Association Between BDNF DNA Methylation and PTSD: A Systematic Meta-Analysis of Human Case–Control Studies

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For making clear how BDNF promoter DNA methylation relate to PTSD, we did this first meta-analysis. Methods: Four case-control studies (617 PTSD patients and 518 controls) published before December 2025 was found from PubMed, Web of Science, CNKI, and Wanfang. Using RevMan 5.4 to do sensitivity analyses, subgroup analyses (promoter I vs. IV), and random-effects meta-analyses. The Newcastle—Ottawa Scale (NOS) was applied for assessing the quality of methods. Results: Pooled BDNF methylation was significantly lower in PTSD than in controls (SMD = − 3.45, 95%CI(-4.45,-2.45), P<0.01), but heterogeneity was high. Subgroup analyses revealed a robust hypomethylation signal for promoter IV, whereas promoter I data showed opposite directional effects and substantial inter-study variance; the combined promoter-I estimate crossed the null line. Sensitivity analyses—alternating effect models, excluding the largest study, and leave-one-out iterations—yielded consistent P < 0.05, indicating a stable overall effect. Funnel-plot asymmetry suggested possible publication bias. Conclusions: The potential of BDNF promoter IV hypomethylation as a peripheral epigenetic biomarker is supported by its continuous association with human PTSD. But for promoter-I part, the findings still not so clear and need bigger studies with proper medicine control to make sure. PTSD BDNF DNA methylation epigenetics meta-analysis biomarker promoter IV Figures Figure 1 Figure 2 Figure 3 Figure 4 1. Introduction A mental illness known as post-traumatic stress disorder (PTSD) can arise following exposure to extremely traumatic situations including physical assault, automobile accidents, or war. Re-experiencing, avoidance, unfavorable changes in mood and cognition, and hyper-arousal are its main symptom clusters [ 1 ]. According to global burden-of-disease studies, the lifetime prevalence is estimated to be around 3.9% globally, with rates exceeding 5.0% in high-income nations and populations with substantial trauma exposure [ 2 ]. PTSD not only makes life worse but also brings higher chance to get depression, anxiety, drug problems and even suicide, so it becomes a big health problem for whole world[ 3 ]. The underlying biological mechanisms of post-traumatic stress disorder (PTSD) are still not fully known, despite established diagnostic criteria and evidence-based psychosocial therapies. As a result, with existing therapies, about half of affected patients have recurring episodes or persistent symptoms. Conventional research has focused on dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis, hyper-reactivity of the amygdala, and reduced prefrontal inhibitory control; however, these changes are insufficient to explain why the illness only affects a portion of people who have experienced trauma [ 4 – 6 ]. Recent research suggests that a crucial biological mediator between environmental stress and brain dysfunction is epigenetic modification, specifically DNA methylation. Methylation in the promoter of the brain-derived neurotrophic factor (BDNF) gene can directly affect transcriptional efficiency, controlling the production and release of BDNF proteins [ 7 ]. Chronic traumatic stress causes methylation alterations in BDNF promoter regions, which lower gene expression in emotion-regulating regions including the hippocampus and prefrontal cortex and trigger behaviors similar to anxiety and depression, according to research on animals [ 8 , 9 ]. Peripheral BDNF protein levels are clinically considerably lower in PTSD patients, and preliminary findings indicate a correlation between promoter methylation status and symptom intensity and illness risk [ 10 ]. However, published results are conflicting: some papers claim hypermethylation or null results, while others reveal hypomethylation at CpG sites within BDNF promoters I and IV [ 11 ]. The validation of BDNF methylation as a legitimate PTSD biomarker has been hindered by small sample sizes (less than 100 patients), varied trauma types, variable CpG locations, and psychotropic drug confounds [ 12 ]. Notably, FKBP5 and NR3C1 have been the focus of previous systematic reviews and meta-analyses, and there is presently no quantitative synthesis of BDNF methylation in PTSD, making it impossible to estimate an overall impact size and impeding translational evaluation [ 13 ]. The majority of investigations have concentrated on particular trauma exposures (like combat-related) or specific ethnic groups, leaving the generalizability of different trauma types and ancestries unresolved [ 14 ]. Cross-sectional designs are the dominant method, but the sparency of targeted analyses of discrete BDNF promoter regions (e.g., promoters I and IV) makes it difficult to discern region-specific roles in PTSD pathogenesis [ 15 ].Furthermore, the uncertainty is further increased as medication use and psychiatric comorbidities have not been adequately addressed [ 16 ]. The lack of clarity on the value of BDNF DNA methylation as a PTSD biomarker has hindered its clinical utility for early recognition and mechanistic research. We searched Chinese and English databases until December 2025 to fix these shortcomings and carried out the first meta-analysis of case-control studies that examined the relationship between BDNF DNA methylation and PTSD. Four investigations (617 PTSD patients and 518 controls) were included. By calculating standardized mean differences (SMDs), assessing heterogeneity and publication bias, and undertaking subgroup and sensitivity analyses, we aimed to: (1) quantify the overall difference in BDNF methylation between PTSD patients and healthy controls; (2) evaluate the influence of promoter region, geographical population, and medication use; and (3) provide an evidence-based foundation for future epigenetic mechanistic studies and precision interventions in PTSD. 2. Materials and Methods 2.1. Data Sources and Search Strategy A systematic literature review was conducted in accordance with PRISMA 2020 guidelines. Four electronic databases were searched without language restriction up to 31 December 2025: CNKI and Wanfang Data (Chinese), PubMed and Web of Science (English). The search strategy combined Medical Subject Headings (MeSH) and free-text terms for PTSD, DNA methylation, and BDNF. The complete Boolean strings are presented in Supplementary Table S1. Reference lists of eligible articles and relevant reviews were manually screened to identify additional records. 2.2. Eligibility Criteria Studies were included if they met all of the following criteria: Case–control design comparing PTSD patients with non-PTSD controls; Quantitative data on CpG-specific or promoter-average BDNF DNA methylation in both groups (mean ± SD or derivable statistics); Peer-reviewed original research published before December 2025. Exclusion criteria were: Reviews, conference abstracts, animal studies, or in vitro experiments; Studies lacking extractable numerical outcomes or separate PTSD group; Duplicate publications or overlapping datasets (the most comprehensive report was retained). 2.3. Data Extraction Two reviewers (X.X. and Y.Y.) independently extracted the following variables using a standardized form: first author, publication year, country/region, study design, PTSD assessment instrument, sample source (tissue or peripheral blood), detection method for methylation, demographic characteristics, and outcome metrics. The primary endpoints were: Promoter I CpG methylation (Kim et al., 2017); Promoter IV CpG methylation (Guo et al., 2018; Hossack et al., 2020). Lee et al. (2022) and Kim et al. (2017) examined identical CpG positions (CpG1 = 688, CpG2 = 686, CpG3 = 682, CpG4 = 675); the remaining two studies did not report genomic coordinates. 2.4. Quality Appraisal Methodological quality was evaluated with the Newcastle–Ottawa Scale (NOS) for case–control studies, which allocates up to nine points across three domains: selection, comparability, and exposure/outcome assessment. Studies scoring 7–9, 4–6, and 0–3 were considered good, fair, and poor quality, respectively. The certainty of evidence was further graded using the GRADE (Grading of Recommendations Assessment, Development and Evaluation) approach. Disagreements were resolved by consensus or consultation with a third reviewer (Z.Z.). Details are provided in Table 1 . Table 1 Newcastle–Ottawa Scale (NOS) Quality Criteria for Case–Control Studies. Study Item # Scoring Criteria Case Selection Adequacy of case definition (Score = 1) ① Yes, with independent validation*; ② Yes, e.g., based on record linkage or self-report; ③ No description. Representativeness of cases(Score = 1) ① Consecutive or otherwise clearly representative case series*; ② Potential for selection bias or not stated. Selection of controls (Score = 1) ① community controls*; ② hospital controls; ③ not described. Definition of controls(Score = 1) ① no history of the target disease (endpoint)*; ② source not described. Comparability of Groups Comparability of cases and controls on the basis of design or analysis(Score = 2) ① study controls for the most important confounding factor(s)*; ② study controls for any additional important confounding factor(s)*. Outcome Assessment Ascertainment of exposure (Score = 1) ① secure record (e.g., surgical records)*; ② structured interview blind to case/control status*; ③ interview not blind to case/control status; ④ written self-report or medical records only; ⑤ no description. Same method of ascertainment for cases and controls(Score = 1) ① yes*; ② no. Non-response rate(Score = 1) ① non-response rate is the same in both groups*; ② non-responders are described*; ③ non-response rate differs and no description is provided. # scoring item; * criterion for awarding the point. 2.5. Statistical Analysis For each trial, the mean and standard deviation of methylation levels at the investigated BDNF promoter CpG sites were extracted. Outcomes that did not reach statistical significance within the original study (P > 0.01) were excluded from the meta-analysis. Between-study heterogeneity was assessed with the Higgins I² statistic and its associated P-value; I² values of 75% were interpreted as absent, low, moderate and high heterogeneity, respectively. A fixed-effect model was used when heterogeneity was negligible or low; otherwise, a random-effects model was applied. Robustness of the pooled estimate was examined by sensitivity analyses. Because the genomic coordinates of the CpG sites differed across studies, subgroup analyses were further conducted according to prespecified study characteristics. All statistical computations were performed with RevMan version 5.4 (Cochrane Collaboration, Copenhagen, Denmark). 3. Results 3.1. Characteristics of the Included Studies The study-selection process is depicted in Fig. 1 . Four English-language publications were found to meet all eligibility criteria in the 72 records identified by the search. In total, these reports included 617 individuals with PTSD and 518 individuals who were not affected by PTSD. Studies showed a variety of trauma exposures, which included combat-related stress, motor vehicle accidents, and physical assault. Case-control design was used in all investigations. The Clinician-Administered PTSD Scale (CAPS), the PTSD Checklist—Military version (PCL-M), or the PTSD Checklist for DSM-5 (PCL-5) were used to establish PTSD diagnoses. Peripheral blood was the source of DNA in every study. Pyrosequencing or MS-SNuPE were used to measure the methylation levels of BDNF promoter CpG sites. Two studies focused on promoter I and two on promoter IV, and Table 2 summarizes their detailed characteristics. Table 2 Basic Characteristics of the Included Studies. Author & year Country Sample size Study type PTSD Assessment Tool Sample Source Detection Method Outcome Measure PTSD Control group Kim et al. 2017 South Korea (Seoul) 126 122 CCS CAPS PB Bisulfite Pyrosequencing BDNF promoter I CpG methylation level Guo et al. 2018 China (Hainan Province) 322 215 CCS CAPS PB MS-SNuPE BDNF promoter IV CpG methylation level Hossack et al. 2020 United States 70 100 CCS PCL-M PB Pyrosequencing BDNF promoter IV CpG meth Lee et al. 2022 South Korea 99 81 CCS PCL-5 PB Pyrosequencing BDNF promoter I CpG methylation level Although Hossack et al. (2020) did not explicitly label the amplicon, the reported genomic coordinates (GRCh37/hg19, chr11:27,743,452 − 27,743,863) map to BDNF promoter IV. We therefore classified these data as promoter-IV methylation. Standard deviations were not provided in the original paper; we derived pooled SDs for each sub-region (BDNF_08 and BDNF_10) from the two-way ANOVA mean-square error and applied these values to all sites within the corresponding amplicon. Quality assessment with the Newcastle–Ottawa Scale yielded scores of 5–7 for the four studies, indicating moderate methodological quality (Table 3 ). The main potential sources of bias were the use of hospital-based rather than community controls and incomplete reporting of non-response rates. Table 3 Summary of Bias Risk Study Item Kim et al. 2017 Guo et al. 2018 Hossack et al. 2020 Lee et al. 2022 Case Selection Adequacy of case definition(Score = 1) √ √ √ √ Representativeness of cases (Score = 1) √ √ × × Selection of controls(Score = 1) × × × √ Definition of controls(Score = 1) √ √ √ √ Comparability of Groups Comparability of cases and controls on the basis of design or analysis(Score = 2) √√ √ √√ √ Outcome Assessment Ascertainment of exposure(Score = 1) × × √ √ Same method of ascertainment for cases and controls(Score = 1) √ √ √ √ Non-response rate(Score = 1) √ × × × Total score 9 7 5 6 6 3.2. Meta-Analytic Results Four case–control studies encompassing 617 PTSD patients and 518 non-PTSD controls (total n = 1135) were retained. The overall heterogeneity was substantial (I² = 100%, P < 0.01); consequently, a random-effects model was applied. The pooled analysis revealed a statistically significant difference in BDNF methylation between the two groups: SMD = − 3.45, 95% CI − 4.45 to − 2.45, P < 0.01, with the confidence interval not crossing the null line (Fig. 2 ). Subgroup analyses indicated low heterogeneity among the CpG sites examined by Kim et al. (2017), Lee et al. (2022) and Hossack et al. (2020). PTSD subjects exhibited significantly lower methylation levels in BDNF promoter IV. In contrast, the two studies evaluating promoter I (Lee et al. 2022; Kim et al. 2017) displayed opposite directions of effect. This discrepancy may be attributable to higher psychotropic medication use in Lee’s cohort, whereas Kim’s observation ran counter to the expected pharmacological influence, suggesting a disease-related signal. When both promoter-I studies were combined, the pooled confidence interval crossed the null, yielding a non-significant summary estimate (Fig. 3 ). Sensitivity analyses affirmed robustness: (i) switching between fixed- and random-effects models, (ii) removing the study with the largest weight, and (iii) conducting a leave-one-out iterative meta-analysis all produced P values < 0.05 and stable effect sizes. Visual inspection of the funnel plot revealed asymmetry, implying potential publication bias (Fig. 4 ). 4. Discussion This systematic review and meta-analysis combines molecular, clinical and case-control data to explain how BDNF promoter DNA methylation connects with PTSD, where the key discovery shows certain BDNF promoter methylation really links to PTSD, supporting earlier clinical findings and giving proof for the "environmental trauma→epigenetic change →brain problem" disease path. Nevertheless, the substantial heterogeneity and directionally opposite effects observed across studies indicate that BDNF methylation is modulated by multiple factors. 4.1. Methodological and Individual Sources of Heterogeneity It seems that the observed heterogeneity is largely caused by differences in study design.Though all four studies used case-control method, but there exist big differences between them. Kim et al. (2017) and Lee et al. (2022) both examined BDNF promoter I, but the latter cohort had a high proportion of participants taking antidepressants or anxiolytics—medications known to modulate epigenetic enzymes and thereby influence BDNF methylation. Direct comparison of absolute methylation values is hindered by variations in laboratory technique (pyrosequencing vs. MS-SNuPE) and precise CpG coordinates analyzed. It is necessary for future research to have harmonized procedures because there are no standardized guidelines for CpG selection or assay protocols. PTSD has inherent individual biological variability, which goes beyond technical factors. Studies specific to cell types show that BDNF methylation can be increased in hippocampal neurons but decreased in microglia after stress, which explains the differing epigenetic responses among cell populations. According to our subgroup analyses, there was a consistent hypomethylation (I2 = 0%) in studies of promoter IV, while studies of promoter I showed contradictory results. The primary role of promoter IV is to regulate BDNF transcription in circuits related to stress (such as the prefrontal cortex and hippocampus), while promoter I has a wider range of regulatory activities and may be more responsive to genetic background and environmental interactions. In order to interpret BDNF-associated findings in PTSD, it is necessary to take into account both region-specific and cell-specific methylation patterns. 4.2. Multilevel Mechanistic Insights Even though there are inconsistencies, BDNF DNA methylation appears to serve as a crucial epigenetic link connecting traumatic exposure to PTSD pathophysiology. Because the prefrontal-amygdala way have BDNF level drop by too much methylation, so the top-down control not strong enough, this make fear reactions last long and spread wide, which in clinic shows as over-excited and always remember bad things. Stress-induced BDNF hypermethylation at the hippocampal level can cause synaptic plasticity to be impaired, resulting in declarative memory deficits and intrusive trauma memories, which is a plausible explanation for the frequent observed declarative memory deficits and intrusive trauma memories in PTSD. BDNF methylation and glucocorticoid-receptor (NR3C1) methylation work together in the neuroendocrine system to counteract negative feedback in the hypothalamic–pituitary–adrenal axis, causing cortisol dysregulation and promoting stress responsiveness. Hypomethylation of BDNF promoter IV shown here has translational potential, especially when combined with other epigenetic signatures, like NR3C1 methylation. Despite the marked heterogeneity, it is important to evaluate trauma history, clinical phenotype, and medication status simultaneously for diagnostic purposes. 5. Limitations Several limitations should be acknowledged.First, although doing subgroup and sensitivity analyses, some unmeasured factors like specific medicine using or CpG sites functional meaning may affect the accuracy. Second, cross-sectional designs are the mainstay of research, so causal inference cannot be made; longitudinal or Mendelian-randomization studies are needed to determine whether BDNF methylation changes are predisposing or resulting from PTSD. Third, sample sizes were modest and populations were restricted to specific ethnic groups and trauma types, which limited generalizability. Negative or small-scale studies may have been overlooked due to our failure to systematically assess publication bias, potentially resulting in an overestimation of effect estimates. 6. Conclusions DNA methylation within specific BDNF promoter regions, specifically promoter IV, is linked to PTSD through strong evidence provided by this meta-analysis. The observed epigenetic modifications likely mediate the translation of environmental stress into pathological phenotypes by modulating neural circuits, hippocampal function and HPA-axis activity. Although heterogeneity is high, BDNF methylation holds promise as an auxiliary biomarker for PTSD. Large-scale, standardized and multi-dimensional investigations are warranted to validate its clinical utility and to inform precision prevention and treatment strategies. Declarations Availability of data and materials The datasets supporting the conclusions of this article are included within the article and its additional files. Competing interests The authors declare that they have no competing interests. Funding This work was supported by the Heilongjiang Provincial Excellent Youth Basic Research Support Program (Project No. PYSCT-2025017); and the Special Research Project on Digital Transformation in Higher Education (Project No. GJX25Z2096). Authors' contributions All authors make substantial contributions to all of the following: The conception and design of the study, or acquisition of data, or analysis and interpretation of data. Drafting the article or revising it critically for important intellectual content. All authors read and approved the final manuscript. Acknowledgements Not applicable References Koenen KC, Ratanatharathorn A, Ng L, McLaughlin KA, Bromet EJ, Stein DJ, Karam EG, Meron Ruscio A, Benjet C, Scott K, Atwoli L, Petukhova M, Lim CCW, Aguilar-Gaxiola S, Al-Hamzawi A, Alonso J, Bunting B, Ciutan M, de Girolamo G, Degenhardt L, Gureje O, Haro JM, Huang Y, Kawakami N, Lee S, Navarro-Mateu F, Pennell BE, Piazza M, Sampson N, Ten Have M, Torres Y, Viana MC, Williams D, Xavier M, Kessler RC. Posttraumatic stress disorder in the World Mental Health Surveys. Psychol Med. 2017 Oct;47(13):2260-2274. doi: 10.1017/S0033291717000708. Epub 2017 Apr 7. PMID: 28385165; PMCID: PMC6034513. Zaretsky TG, Jagodnik KM, Barsic R, Antonio JH, Bonanno PA, MacLeod C, Pierce C, Carney H, Morrison MT, Saylor C, Danias G, Lepow L, Yehuda R. The Psychedelic Future of Post-Traumatic Stress Disorder Treatment. Curr Neuropharmacol. 2024;22(4):636-735. doi: 10.2174/1570159X22666231027111147. PMID: 38284341; PMCID: PMC10845102. Kessler RC, Chiu WT, Demler O, Merikangas KR, Walters EE. Prevalence, severity, and comorbidity of 12-month DSM-IV disorders in the National Comorbidity Survey Replication. Arch Gen Psychiatry. 2005 Jun;62(6):617-27. doi: 10.1001/archpsyc.62.6.617. Erratum in: Arch Gen Psychiatry. 2005 Jul;62(7):709. Merikangas, Kathleen R [added]. PMID: 15939839; PMCID: PMC2847357. Yehuda R, LeDoux J. Response variation following trauma: a translational neuroscience approach to understanding PTSD. Neuron. 2007 Oct 4;56(1):19-32. doi: 10.1016/j.neuron.2007.09.006. PMID: 17920012. Shalev A, Cho D, Marmar CR. Neurobiology and Treatment of Posttraumatic Stress Disorder. Am J Psychiatry. 2024 Aug 1;181(8):705-719. doi: 10.1176/appi.ajp.20240536. PMID: 39086292. Koenen KC, Ratanatharathorn A, Ng L, McLaughlin KA, Bromet EJ, Stein DJ, Karam EG, Meron Ruscio A, Benjet C, Scott K, Atwoli L, Petukhova M, Lim CCW, Aguilar-Gaxiola S, Al-Hamzawi A, Alonso J, Bunting B, Ciutan M, de Girolamo G, Degenhardt L, Gureje O, Haro JM, Huang Y, Kawakami N, Lee S, Navarro-Mateu F, Pennell BE, Piazza M, Sampson N, Ten Have M, Torres Y, Viana MC, Williams D, Xavier M, Kessler RC. Posttraumatic stress disorder in the World Mental Health Surveys. Psychol Med. 2017 Oct;47(13):2260-2274. doi: 10.1017/S0033291717000708. Epub 2017 Apr 7. PMID: 28385165; PMCID: PMC6034513. Nasca C, Zelli D, Bigio B, Piccinin S, Scaccianoce S, Nisticò R, McEwen BS. Stress dynamically regulates behavior and glutamatergic gene expression in hippocampus by opening a window of epigenetic plasticity. Proc Natl Acad Sci U S A. 2015 Dec 1;112(48):14960-5. doi: 10.1073/pnas.1516016112. Epub 2015 Nov 16. PMID: 26627246; PMCID: PMC4672825. Wang F, Li Z, Li B, Xu M, Wang Y, Wang J, Li J, Zhu Y, He L, Ma J, Mao L, Xu X, Li X, Zhang H, Yang J, Zhang K, Wu C. Xiaochaihutang ameliorates depression-like behaviors induced via chronic social defeat stress by regulating exon-specific Bdnf transcription through H3K18 acetylation in the hippocampus of mice. Phytomedicine. 2025 May;140:156567. doi: 10.1016/j.phymed.2025.156567. Epub 2025 Mar 3. PMID: 40068295. Roth TL, Zoladz PR, Sweatt JD, Diamond DM. Epigenetic modification of hippocampal Bdnf DNA in adult rats in an animal model of post-traumatic stress disorder. J Psychiatr Res. 2011 Jul;45(7):919-26. doi: 10.1016/j.jpsychires.2011.01.013. Epub 2011 Feb 9. PMID: 21306736; PMCID: PMC3335738. Fungaro Rissatti L, Wilson D, Palace-Berl F, de Mello Ponteciano B, Sardela de Miranda F, Alece Arantes Moreno I, Dos Santos Vieira T, Pereira Sorroche B, Rebolho Batista Arantes LM, Madeira Alvares da Silva A, D'Almeida V, Demarzo M, Rodrigues de Oliveira D. BDNF methylation associated with stress in women: Novel insights in epigenetics and inflammation. Brain Behav Immun Health. 2024 Oct 31;42:100900. doi: 10.1016/j.bbih.2024.100900. PMID: 39552782; PMCID: PMC11565430. Kim TY, Kim SJ, Chung HG, Choi JH, Kim SH, Kang JI. Epigenetic alterations of the BDNF gene in combat-related post-traumatic stress disorder. Acta Psychiatr Scand. 2017 Feb;135(2):170-179. doi: 10.1111/acps.12675. Epub 2016 Nov 25. PMID: 27886370. Tseilikman VE, Tseilikman OB, Pashkov AA, Ivleva IS, Karpenko MN, Shatilov VA, Zhukov MS, Fedotova JO, Kondashevskaya MV, Downey HF, Manukhina EB. Mechanisms of Susceptibility and Resilience to PTSD: Role of Dopamine Metabolism and BDNF Expression in the Hippocampus. Int J Mol Sci. 2022 Nov 23;23(23):14575. doi: 10.3390/ijms232314575. PMID: 36498900; PMCID: PMC9737079. Alahmad R, Hinchey LM, Shaikh M, Amirsadri A, Javanbakht A. Gene expression and epigenetic changes in post-traumatic stress disorder, depression, and anxiety in first responders: A systematic review. J Psychiatr Res. 2025 Feb;182:438-451. doi: 10.1016/j.jpsychires.2025.01.032. Epub 2025 Jan 23. PMID: 39892213. Golubeva E, Zeltser A, Zorkina Y, Ochneva A, Tsurina A, Andreyuk D, Kostyuk G, Morozova A. Epigenetic Alterations in Post-Traumatic Stress Disorder: Comprehensive Review of Molecular Markers. Complex Psychiatry. 2024 Nov 18;10(1-4):71-107. doi: 10.1159/000541822. PMID: 39564465; PMCID: PMC11573359. Lipov EG, Candido K, Ritchie EC. Possible Reversal of PTSD-Related DNA Methylation by Sympathetic Blockade. J Mol Neurosci. 2017 May;62(1):67-72. doi: 10.1007/s12031-017-0911-3. Epub 2017 Mar 31. PMID: 28364364. Veltri A, Nicolì V, Marino R, Rea F, Corsi M, Chiumiento M, Giangreco M, Caldi F, Guglielmi G, Foddis R, Coppedè F, Silvestri R, Buselli R. Plasma Brain-Derived Neurotrophic Factor (BDNF) Levels and BDNF Promoters' DNA Methylation in Workers Exposed to Occupational Stress and Suffering from Psychiatric Disorders. Brain Sci. 2024 Oct 30;14(11):1106. doi: 10.3390/brainsci14111106. PMID: 39595869; PMCID: PMC11592044. Kim TY, Kim SJ, Chung HG, Choi JH, Kim SH, Kang JI. Epigenetic alterations of the BDNF gene in combat-related post-traumatic stress disorder. Acta Psychiatr Scand. 2017;135(2):170-179. doi: 10.1111/acps.12675. PMID: 27886370. Lee HS, Kwon A, Lee SH. Oxytocin receptor genes moderate BDNF epigenetic methylation by childhood trauma. J Affect Disord. 2022;306:167-173. doi: 10.1016/j.jad.2022.03.020. PMID: 35314247. Guo JC, Yang YJ, Zheng XA, Jiang XL, Guo M, Wang XD, et al. CpG methylation of brain-derived neurotrophic factor gene promoter as a potent diagnostic and prognostic biomarker for post-traumatic stress disorder. Int J Clin Exp Pathol. 2018;11(10):5101-5109. PMID: 31949588; PMCID: PMC6962936. Hossack MR, Reid MW, Aden JK, Gibbons T, Noe JC, Willis AM. Adverse Childhood Experience, Genes, and PTSD Risk in Soldiers: A Methylation Study. Mil Med. 2020;185(3-4):377-384. doi: 10.1093/milmed/usz292. PMID: 32976583. Roth, T. L., Matt, S., Chen, K., & Blaze, J. (2014). Bdnf DNA methylation modifications in the hippocampus and amygdala of male and female rats exposed to different caregiving environments outside the homecage. Developmental Psychobiology, 56(8), 1726-1740. doi: 10.1002/dev.21218. Epub 2014 Apr 21. de la Torre, R., Montero-Marin, J., Pérez-Caballero, D., et al. (2023). Plasma Brain-Derived Neurotrophic Factor (BDNF) Levels and BDNF Promoters' DNA Methylation in Workers Exposed to Occupational Stress and Suffering from Psychiatric Disorders. International Journal of Environmental Research and Public Health, 20(22), 8215. doi: 10.3390/brainsci14111106. PMID: 39595869; PMCID: PMC11592044. Chou PC, Huang YC, Yu S. Mechanisms of Epigenetic Inheritance in Post-Traumatic Stress Disorder. Life (Basel). 2024 Jan 8;14(1):98. doi: 10.3390/life14010098. PMID: 38255713; PMCID: PMC10817356. Nibuya M, Morinobu S, Duman RS. Regulation of BDNF and trkB mRNA in rat brain by chronic electroconvulsive seizure and antidepressant drug treatments. J Neurosci. 1995 Nov;15(11):7539-47. doi: 10.1523/JNEUROSCI.15-11-07539.1995. PMID: 7472505; PMCID: PMC6578063. Shao SH, Shi SS, Li ZL, Zhao MS, Xie SY, Pan F. Aging effects on the BDNF mRNA and TrkB mRNA expression of the hippocampus in different durations of stress. Chin J Physiol. 2010 Oct 31;53(5):285-93. doi: 10.4077/cjp.2010.amk056. Erratum in: Chin J Physiol. 2010 Dec 31;53(6):472. PMID: 21793339. Park C, Rosenblat JD, Brietzke E, Pan Z, Lee Y, Cao B, Zuckerman H, Kalantarova A, McIntyre RS. Stress, epigenetics and depression: A systematic review. Neurosci Biobehav Rev. 2019 Jul;102:139-152. doi: 10.1016/j.neubiorev.2019.04.010. Epub 2019 Apr 18. PMID: 31005627. 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Wang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAzElEQVRIiWNgGAWjYBACxvbmw4///LCp72dvIFILc8+xNAPenjTGmT0HiNTCPsNHQYKH7TDjhhsJRGrhncHDYCDBw8xscPPxxhsMNTbRBLVIzu498MDAgo1N8nZasQXDsbTcBkJaDOecSzBI4OHh4budYybB2HCYsBb7GzkGEgfYJCQYbp4hUgvjjBwDyQY2AwOBGzzEagEGsjFjT0KCZA/QLwnE+AUclQw//ifwsx/eeONDjQ1hLcjAQCKBFOUQLaTqGAWjYBSMgpEBALQpQZRcR9/NAAAAAElFTkSuQmCC","orcid":"","institution":"Heilongjiang University","correspondingAuthor":true,"prefix":"","firstName":"Lin","middleName":"","lastName":"Wang","suffix":""},{"id":572148630,"identity":"0cd1c9aa-7aaa-4550-b2fd-e8e9a4b71a2d","order_by":1,"name":"Zehao Yan","email":"","orcid":"","institution":"Heilongjiang University","correspondingAuthor":false,"prefix":"","firstName":"Zehao","middleName":"","lastName":"Yan","suffix":""}],"badges":[],"createdAt":"2026-01-02 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10:22:16","extension":"xml","order_by":11,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":94087,"visible":true,"origin":"","legend":"","description":"","filename":"aad65a9a2b084dc09947b91513dab4a11structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-8497887/v1/f83375f410c51cdf1b7160b8.xml"},{"id":100132071,"identity":"f6518359-5187-4cb0-b030-91c3910128c0","added_by":"auto","created_at":"2026-01-13 10:22:16","extension":"html","order_by":12,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":107084,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-8497887/v1/39291eb6c3e1f48dea3cf075.html"},{"id":100132055,"identity":"79aa9702-8a72-41c3-8e34-96dc42de866c","added_by":"auto","created_at":"2026-01-13 10:22:16","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":107223,"visible":true,"origin":"","legend":"\u003cp\u003eStudy selection flowchart.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-8497887/v1/fbe0f345e9511cfd87357012.png"},{"id":100132057,"identity":"ef011eae-5a5c-466b-b42d-793a0cc2570c","added_by":"auto","created_at":"2026-01-13 10:22:16","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":21746,"visible":true,"origin":"","legend":"\u003cp\u003eForest plot of the meta-analysis.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-8497887/v1/49aa7f7a394b07a5bc9956f1.png"},{"id":100366637,"identity":"8d6e7388-0169-44bd-a7c0-9995c9c9629e","added_by":"auto","created_at":"2026-01-16 07:56:25","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":34886,"visible":true,"origin":"","legend":"\u003cp\u003eForest plot of the subgroup analysis.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-8497887/v1/4ec78074597e4f444fff5bc2.png"},{"id":100367961,"identity":"3be19fa3-e6a9-45b3-914e-386e213bc71e","added_by":"auto","created_at":"2026-01-16 07:57:28","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":5300,"visible":true,"origin":"","legend":"\u003cp\u003eFunnel plot.\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-8497887/v1/9a38a618dd8c64a2826aa2da.png"},{"id":107854666,"identity":"ecd4850d-c955-4a8f-bf54-21199055e0cf","added_by":"auto","created_at":"2026-04-27 03:25:19","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":458067,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8497887/v1/373e4783-6cc9-4e34-aca8-cf6ddef88c3c.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Association Between BDNF DNA Methylation and PTSD: A Systematic Meta-Analysis of Human Case–Control Studies","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eA mental illness known as post-traumatic stress disorder (PTSD) can arise following exposure to extremely traumatic situations including physical assault, automobile accidents, or war. Re-experiencing, avoidance, unfavorable changes in mood and cognition, and hyper-arousal are its main symptom clusters [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. According to global burden-of-disease studies, the lifetime prevalence is estimated to be around 3.9% globally, with rates exceeding 5.0% in high-income nations and populations with substantial trauma exposure [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. PTSD not only makes life worse but also brings higher chance to get depression, anxiety, drug problems and even suicide, so it becomes a big health problem for whole world[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe underlying biological mechanisms of post-traumatic stress disorder (PTSD) are still not fully known, despite established diagnostic criteria and evidence-based psychosocial therapies. As a result, with existing therapies, about half of affected patients have recurring episodes or persistent symptoms. Conventional research has focused on dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis, hyper-reactivity of the amygdala, and reduced prefrontal inhibitory control; however, these changes are insufficient to explain why the illness only affects a portion of people who have experienced trauma [\u003cspan additionalcitationids=\"CR5\" citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eRecent research suggests that a crucial biological mediator between environmental stress and brain dysfunction is epigenetic modification, specifically DNA methylation. Methylation in the promoter of the brain-derived neurotrophic factor (BDNF) gene can directly affect transcriptional efficiency, controlling the production and release of BDNF proteins [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. Chronic traumatic stress causes methylation alterations in BDNF promoter regions, which lower gene expression in emotion-regulating regions including the hippocampus and prefrontal cortex and trigger behaviors similar to anxiety and depression, according to research on animals [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Peripheral BDNF protein levels are clinically considerably lower in PTSD patients, and preliminary findings indicate a correlation between promoter methylation status and symptom intensity and illness risk [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eHowever, published results are conflicting: some papers claim hypermethylation or null results, while others reveal hypomethylation at CpG sites within BDNF promoters I and IV [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. The validation of BDNF methylation as a legitimate PTSD biomarker has been hindered by small sample sizes (less than 100 patients), varied trauma types, variable CpG locations, and psychotropic drug confounds [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Notably, FKBP5 and NR3C1 have been the focus of previous systematic reviews and meta-analyses, and there is presently no quantitative synthesis of BDNF methylation in PTSD, making it impossible to estimate an overall impact size and impeding translational evaluation [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe majority of investigations have concentrated on particular trauma exposures (like combat-related) or specific ethnic groups, leaving the generalizability of different trauma types and ancestries unresolved [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. Cross-sectional designs are the dominant method, but the sparency of targeted analyses of discrete BDNF promoter regions (e.g., promoters I and IV) makes it difficult to discern region-specific roles in PTSD pathogenesis [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e].Furthermore, the uncertainty is further increased as medication use and psychiatric comorbidities have not been adequately addressed [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. The lack of clarity on the value of BDNF DNA methylation as a PTSD biomarker has hindered its clinical utility for early recognition and mechanistic research.\u003c/p\u003e \u003cp\u003eWe searched Chinese and English databases until December 2025 to fix these shortcomings and carried out the first meta-analysis of case-control studies that examined the relationship between BDNF DNA methylation and PTSD. Four investigations (617 PTSD patients and 518 controls) were included. By calculating standardized mean differences (SMDs), assessing heterogeneity and publication bias, and undertaking subgroup and sensitivity analyses, we aimed to: (1) quantify the overall difference in BDNF methylation between PTSD patients and healthy controls; (2) evaluate the influence of promoter region, geographical population, and medication use; and (3) provide an evidence-based foundation for future epigenetic mechanistic studies and precision interventions in PTSD.\u003c/p\u003e"},{"header":"2. Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1. Data Sources and Search Strategy\u003c/h2\u003e \u003cp\u003eA systematic literature review was conducted in accordance with PRISMA 2020 guidelines. Four electronic databases were searched without language restriction up to 31 December 2025: CNKI and Wanfang Data (Chinese), PubMed and Web of Science (English). The search strategy combined Medical Subject Headings (MeSH) and free-text terms for PTSD, DNA methylation, and BDNF. The complete Boolean strings are presented in Supplementary Table S1. Reference lists of eligible articles and relevant reviews were manually screened to identify additional records.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2. Eligibility Criteria\u003c/h2\u003e \u003cp\u003eStudies were included if they met all of the following criteria:\u003c/p\u003e \u003cp\u003e \u003col\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eCase\u0026ndash;control design comparing PTSD patients with non-PTSD controls;\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eQuantitative data on CpG-specific or promoter-average BDNF DNA methylation in both groups (mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD or derivable statistics);\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003ePeer-reviewed original research published before December 2025.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003c/ol\u003e \u003c/p\u003e \u003cp\u003eExclusion criteria were:\u003c/p\u003e \u003cp\u003e \u003col\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eReviews, conference abstracts, animal studies, or in vitro experiments;\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eStudies lacking extractable numerical outcomes or separate PTSD group;\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eDuplicate publications or overlapping datasets (the most comprehensive report was retained).\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003c/ol\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3. Data Extraction\u003c/h2\u003e \u003cp\u003eTwo reviewers (X.X. and Y.Y.) independently extracted the following variables using a standardized form: first author, publication year, country/region, study design, PTSD assessment instrument, sample source (tissue or peripheral blood), detection method for methylation, demographic characteristics, and outcome metrics. The primary endpoints were:\u003c/p\u003e \u003cp\u003e \u003col\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003ePromoter I CpG methylation (Kim et al., 2017);\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003ePromoter IV CpG methylation (Guo et al., 2018; Hossack et al., 2020).\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003c/ol\u003e \u003c/p\u003e \u003cp\u003eLee et al. (2022) and Kim et al. (2017) examined identical CpG positions (CpG1\u0026thinsp;=\u0026thinsp;688, CpG2\u0026thinsp;=\u0026thinsp;686, CpG3\u0026thinsp;=\u0026thinsp;682, CpG4\u0026thinsp;=\u0026thinsp;675); the remaining two studies did not report genomic coordinates.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4. Quality Appraisal\u003c/h2\u003e \u003cp\u003eMethodological quality was evaluated with the Newcastle\u0026ndash;Ottawa Scale (NOS) for case\u0026ndash;control studies, which allocates up to nine points across three domains: selection, comparability, and exposure/outcome assessment. Studies scoring 7\u0026ndash;9, 4\u0026ndash;6, and 0\u0026ndash;3 were considered good, fair, and poor quality, respectively. The certainty of evidence was further graded using the GRADE (Grading of Recommendations Assessment, Development and Evaluation) approach. Disagreements were resolved by consensus or consultation with a third reviewer (Z.Z.). Details are provided in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eNewcastle\u0026ndash;Ottawa Scale (NOS) Quality Criteria for Case\u0026ndash;Control Studies.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eStudy\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eItem\u003csup\u003e#\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eScoring Criteria\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003eCase Selection\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAdequacy of case definition (Score\u0026thinsp;=\u0026thinsp;1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e① Yes, with independent validation*;\u003c/p\u003e \u003cp\u003e② Yes, e.g., based on record linkage or self-report;\u003c/p\u003e \u003cp\u003e③ No description.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRepresentativeness of cases(Score\u0026thinsp;=\u0026thinsp;1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e① Consecutive or otherwise clearly representative case series*;\u003c/p\u003e \u003cp\u003e② Potential for selection bias or not stated.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSelection of controls (Score\u0026thinsp;=\u0026thinsp;1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e① community controls*; ② hospital controls; ③ not described.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDefinition of controls(Score\u0026thinsp;=\u0026thinsp;1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e① no history of the target disease (endpoint)*; ② source not described.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eComparability of Groups\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eComparability of cases and controls on the basis of design or analysis(Score\u0026thinsp;=\u0026thinsp;2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e① study controls for the most important confounding factor(s)*; ② study controls for any additional important confounding factor(s)*.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eOutcome Assessment\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAscertainment of exposure (Score\u0026thinsp;=\u0026thinsp;1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e① secure record (e.g., surgical records)*;\u003c/p\u003e \u003cp\u003e② structured interview blind to case/control status*;\u003c/p\u003e \u003cp\u003e③ interview not blind to case/control status;\u003c/p\u003e \u003cp\u003e④ written self-report or medical records only;\u003c/p\u003e \u003cp\u003e⑤ no description.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSame method of ascertainment for cases and controls(Score\u0026thinsp;=\u0026thinsp;1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e① yes*; ② no.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNon-response rate(Score\u0026thinsp;=\u0026thinsp;1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e① non-response rate is the same in both groups*;\u003c/p\u003e \u003cp\u003e② non-responders are described*;\u003c/p\u003e \u003cp\u003e③ non-response rate differs and no description is provided.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e# scoring item; * criterion for awarding the point.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.5. Statistical Analysis\u003c/h2\u003e \u003cp\u003eFor each trial, the mean and standard deviation of methylation levels at the investigated BDNF promoter CpG sites were extracted. Outcomes that did not reach statistical significance within the original study (P\u0026thinsp;\u0026gt;\u0026thinsp;0.01) were excluded from the meta-analysis. Between-study heterogeneity was assessed with the Higgins I\u0026sup2; statistic and its associated P-value; I\u0026sup2; values of \u0026lt;\u0026thinsp;25%, 25\u0026ndash;50%, 50\u0026ndash;75% and \u0026gt;\u0026thinsp;75% were interpreted as absent, low, moderate and high heterogeneity, respectively. A fixed-effect model was used when heterogeneity was negligible or low; otherwise, a random-effects model was applied.\u003c/p\u003e \u003cp\u003eRobustness of the pooled estimate was examined by sensitivity analyses. Because the genomic coordinates of the CpG sites differed across studies, subgroup analyses were further conducted according to prespecified study characteristics. All statistical computations were performed with RevMan version 5.4 (Cochrane Collaboration, Copenhagen, Denmark).\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results","content":"\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e3.1. Characteristics of the Included Studies\u003c/h2\u003e \u003cp\u003eThe study-selection process is depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. Four English-language publications were found to meet all eligibility criteria in the 72 records identified by the search. In total, these reports included 617 individuals with PTSD and 518 individuals who were not affected by PTSD. Studies showed a variety of trauma exposures, which included combat-related stress, motor vehicle accidents, and physical assault. Case-control design was used in all investigations. The Clinician-Administered PTSD Scale (CAPS), the PTSD Checklist\u0026mdash;Military version (PCL-M), or the PTSD Checklist for DSM-5 (PCL-5) were used to establish PTSD diagnoses. Peripheral blood was the source of DNA in every study. Pyrosequencing or MS-SNuPE were used to measure the methylation levels of BDNF promoter CpG sites. Two studies focused on promoter I and two on promoter IV, and Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e summarizes their detailed characteristics.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eBasic Characteristics of the Included Studies.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"9\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eAuthor \u0026amp; year\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eCountry\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003eSample size\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eStudy type\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ePTSD Assessment Tool\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eSample Source\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eDetection Method\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eOutcome Measure\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePTSD\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eControl group\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eKim et al. 2017\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSouth Korea (Seoul)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e126\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e122\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eCCS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eCAPS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003ePB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003eBisulfite Pyrosequencing\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003eBDNF promoter I CpG methylation level\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGuo et al. 2018\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina (Hainan Province)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e322\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e215\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eCCS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eCAPS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003ePB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003eMS-SNuPE\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003eBDNF promoter IV CpG methylation level\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHossack et al. 2020\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eUnited States\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e70\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e100\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eCCS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePCL-M\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003ePB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003ePyrosequencing\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003eBDNF promoter IV CpG meth\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLee et al. 2022\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSouth Korea\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e99\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e81\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eCCS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePCL-5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003ePB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003ePyrosequencing\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003eBDNF promoter I CpG methylation level\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eAlthough Hossack et al. (2020) did not explicitly label the amplicon, the reported genomic coordinates (GRCh37/hg19, chr11:27,743,452\u0026thinsp;\u0026minus;\u0026thinsp;27,743,863) map to BDNF promoter IV. We therefore classified these data as promoter-IV methylation. Standard deviations were not provided in the original paper; we derived pooled SDs for each sub-region (BDNF_08 and BDNF_10) from the two-way ANOVA mean-square error and applied these values to all sites within the corresponding amplicon.\u003c/p\u003e \u003cp\u003eQuality assessment with the Newcastle\u0026ndash;Ottawa Scale yielded scores of 5\u0026ndash;7 for the four studies, indicating moderate methodological quality (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The main potential sources of bias were the use of hospital-based rather than community controls and incomplete reporting of non-response rates.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eSummary of Bias Risk\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eStudy\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eItem\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eKim et al. 2017\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eGuo et al. 2018\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eHossack et al. 2020\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eLee et al. 2022\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003eCase Selection\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAdequacy of case definition(Score\u0026thinsp;=\u0026thinsp;1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u0026radic;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026radic;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026radic;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u0026radic;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRepresentativeness of cases (Score\u0026thinsp;=\u0026thinsp;1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u0026radic;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026radic;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026times;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u0026times;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSelection of controls(Score\u0026thinsp;=\u0026thinsp;1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u0026times;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026times;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026times;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u0026radic;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDefinition of controls(Score\u0026thinsp;=\u0026thinsp;1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u0026radic;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026radic;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026radic;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u0026radic;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eComparability of Groups\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eComparability of cases and controls on the basis of design or analysis(Score\u0026thinsp;=\u0026thinsp;2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u0026radic;\u0026radic;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026radic;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026radic;\u0026radic;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u0026radic;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eOutcome Assessment\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAscertainment of exposure(Score\u0026thinsp;=\u0026thinsp;1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u0026times;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026times;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026radic;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u0026radic;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSame method of ascertainment for cases and controls(Score\u0026thinsp;=\u0026thinsp;1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u0026radic;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026radic;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026radic;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u0026radic;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNon-response rate(Score\u0026thinsp;=\u0026thinsp;1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u0026radic;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026times;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026times;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u0026times;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTotal score\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e3.2. Meta-Analytic Results\u003c/h2\u003e \u003cp\u003eFour case\u0026ndash;control studies encompassing 617 PTSD patients and 518 non-PTSD controls (total n\u0026thinsp;=\u0026thinsp;1135) were retained. The overall heterogeneity was substantial (I\u0026sup2; = 100%, P\u0026thinsp;\u0026lt;\u0026thinsp;0.01); consequently, a random-effects model was applied. The pooled analysis revealed a statistically significant difference in BDNF methylation between the two groups: SMD = \u0026minus;\u0026thinsp;3.45, 95% CI \u0026minus;\u0026thinsp;4.45 to \u0026minus;\u0026thinsp;2.45, P\u0026thinsp;\u0026lt;\u0026thinsp;0.01, with the confidence interval not crossing the null line (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eSubgroup analyses indicated low heterogeneity among the CpG sites examined by Kim et al. (2017), Lee et al. (2022) and Hossack et al. (2020). PTSD subjects exhibited significantly lower methylation levels in BDNF promoter IV. In contrast, the two studies evaluating promoter I (Lee et al. 2022; Kim et al. 2017) displayed opposite directions of effect. This discrepancy may be attributable to higher psychotropic medication use in Lee\u0026rsquo;s cohort, whereas Kim\u0026rsquo;s observation ran counter to the expected pharmacological influence, suggesting a disease-related signal. When both promoter-I studies were combined, the pooled confidence interval crossed the null, yielding a non-significant summary estimate (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eSensitivity analyses affirmed robustness: (i) switching between fixed- and random-effects models, (ii) removing the study with the largest weight, and (iii) conducting a leave-one-out iterative meta-analysis all produced P values\u0026thinsp;\u0026lt;\u0026thinsp;0.05 and stable effect sizes. Visual inspection of the funnel plot revealed asymmetry, implying potential publication bias (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4. Discussion","content":"\u003cp\u003eThis systematic review and meta-analysis combines molecular, clinical and case-control data to explain how BDNF promoter DNA methylation connects with PTSD, where the key discovery shows certain BDNF promoter methylation really links to PTSD, supporting earlier clinical findings and giving proof for the \"environmental trauma\u0026rarr;epigenetic change \u0026rarr;brain problem\" disease path. Nevertheless, the substantial heterogeneity and directionally opposite effects observed across studies indicate that BDNF methylation is modulated by multiple factors.\u003c/p\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003e4.1. Methodological and Individual Sources of Heterogeneity\u003c/h2\u003e \u003cp\u003eIt seems that the observed heterogeneity is largely caused by differences in study design.Though all four studies used case-control method, but there exist big differences between them. Kim et al. (2017) and Lee et al. (2022) both examined BDNF promoter I, but the latter cohort had a high proportion of participants taking antidepressants or anxiolytics\u0026mdash;medications known to modulate epigenetic enzymes and thereby influence BDNF methylation. Direct comparison of absolute methylation values is hindered by variations in laboratory technique (pyrosequencing vs. MS-SNuPE) and precise CpG coordinates analyzed. It is necessary for future research to have harmonized procedures because there are no standardized guidelines for CpG selection or assay protocols.\u003c/p\u003e \u003cp\u003ePTSD has inherent individual biological variability, which goes beyond technical factors. Studies specific to cell types show that BDNF methylation can be increased in hippocampal neurons but decreased in microglia after stress, which explains the differing epigenetic responses among cell populations. According to our subgroup analyses, there was a consistent hypomethylation (I2\u0026thinsp;=\u0026thinsp;0%) in studies of promoter IV, while studies of promoter I showed contradictory results. The primary role of promoter IV is to regulate BDNF transcription in circuits related to stress (such as the prefrontal cortex and hippocampus), while promoter I has a wider range of regulatory activities and may be more responsive to genetic background and environmental interactions. In order to interpret BDNF-associated findings in PTSD, it is necessary to take into account both region-specific and cell-specific methylation patterns.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003e4.2. Multilevel Mechanistic Insights\u003c/h2\u003e \u003cp\u003eEven though there are inconsistencies, BDNF DNA methylation appears to serve as a crucial epigenetic link connecting traumatic exposure to PTSD pathophysiology.\u003c/p\u003e \u003cp\u003eBecause the prefrontal-amygdala way have BDNF level drop by too much methylation, so the top-down control not strong enough, this make fear reactions last long and spread wide, which in clinic shows as over-excited and always remember bad things.\u003c/p\u003e \u003cp\u003eStress-induced BDNF hypermethylation at the hippocampal level can cause synaptic plasticity to be impaired, resulting in declarative memory deficits and intrusive trauma memories, which is a plausible explanation for the frequent observed declarative memory deficits and intrusive trauma memories in PTSD.\u003c/p\u003e \u003cp\u003eBDNF methylation and glucocorticoid-receptor (NR3C1) methylation work together in the neuroendocrine system to counteract negative feedback in the hypothalamic\u0026ndash;pituitary\u0026ndash;adrenal axis, causing cortisol dysregulation and promoting stress responsiveness.\u003c/p\u003e \u003cp\u003eHypomethylation of BDNF promoter IV shown here has translational potential, especially when combined with other epigenetic signatures, like NR3C1 methylation. Despite the marked heterogeneity, it is important to evaluate trauma history, clinical phenotype, and medication status simultaneously for diagnostic purposes.\u003c/p\u003e \u003c/div\u003e"},{"header":"5. Limitations","content":"\u003cp\u003eSeveral limitations should be acknowledged.First, although doing subgroup and sensitivity analyses, some unmeasured factors like specific medicine using or CpG sites functional meaning may affect the accuracy. Second, cross-sectional designs are the mainstay of research, so causal inference cannot be made; longitudinal or Mendelian-randomization studies are needed to determine whether BDNF methylation changes are predisposing or resulting from PTSD. Third, sample sizes were modest and populations were restricted to specific ethnic groups and trauma types, which limited generalizability. Negative or small-scale studies may have been overlooked due to our failure to systematically assess publication bias, potentially resulting in an overestimation of effect estimates.\u003c/p\u003e"},{"header":"6. Conclusions","content":"\u003cp\u003eDNA methylation within specific BDNF promoter regions, specifically promoter IV, is linked to PTSD through strong evidence provided by this meta-analysis. The observed epigenetic modifications likely mediate the translation of environmental stress into pathological phenotypes by modulating neural circuits, hippocampal function and HPA-axis activity. Although heterogeneity is high, BDNF methylation holds promise as an auxiliary biomarker for PTSD. Large-scale, standardized and multi-dimensional investigations are warranted to validate its clinical utility and to inform precision prevention and treatment strategies.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cem\u003eAvailability of data and materials\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets supporting the conclusions of this article are included within the article and its additional files.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eCompeting interests\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eFunding\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by the Heilongjiang Provincial Excellent Youth Basic Research Support Program \u0026nbsp;(Project No. PYSCT-2025017); and the Special Research Project on Digital Transformation in Higher Education \u0026nbsp;(Project No. GJX25Z2096).\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eAuthors\u0026apos; contributions\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eAll authors make substantial contributions to all of the following:\u003c/p\u003e\n\u003cp\u003eThe conception and design of the study, or acquisition of data, or analysis and interpretation of data.\u003c/p\u003e\n\u003cp\u003eDrafting the article or revising it critically for important intellectual content.\u003c/p\u003e\n\u003cp\u003eAll authors read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eAcknowledgements\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eKoenen KC, Ratanatharathorn A, Ng L, McLaughlin KA, Bromet EJ, Stein DJ, Karam EG, Meron Ruscio A, Benjet C, Scott K, Atwoli L, Petukhova M, Lim CCW, Aguilar-Gaxiola S, Al-Hamzawi A, Alonso J, Bunting B, Ciutan M, de Girolamo G, Degenhardt L, Gureje O, Haro JM, Huang Y, Kawakami N, Lee S, Navarro-Mateu F, Pennell BE, Piazza M, Sampson N, Ten Have M, Torres Y, Viana MC, Williams D, Xavier M, Kessler RC. Posttraumatic stress disorder in the World Mental Health Surveys. Psychol Med. 2017 Oct;47(13):2260-2274. doi: 10.1017/S0033291717000708. Epub 2017 Apr 7. PMID: 28385165; PMCID: PMC6034513.\u003c/li\u003e\n \u003cli\u003eZaretsky TG, Jagodnik KM, Barsic R, Antonio JH, Bonanno PA, MacLeod C, Pierce C, Carney H, Morrison MT, Saylor C, Danias G, Lepow L, Yehuda R. The Psychedelic Future of Post-Traumatic Stress Disorder Treatment. Curr Neuropharmacol. 2024;22(4):636-735. doi: 10.2174/1570159X22666231027111147. PMID: 38284341; PMCID: PMC10845102.\u003c/li\u003e\n \u003cli\u003eKessler RC, Chiu WT, Demler O, Merikangas KR, Walters EE. Prevalence, severity, and comorbidity of 12-month DSM-IV disorders in the National Comorbidity Survey Replication. Arch Gen Psychiatry. 2005 Jun;62(6):617-27. doi: 10.1001/archpsyc.62.6.617. Erratum in: Arch Gen Psychiatry. 2005 Jul;62(7):709. Merikangas, Kathleen R [added]. PMID: 15939839; PMCID: PMC2847357.\u003c/li\u003e\n \u003cli\u003eYehuda R, LeDoux J. Response variation following trauma: a translational neuroscience approach to understanding PTSD. Neuron. 2007 Oct 4;56(1):19-32. doi: 10.1016/j.neuron.2007.09.006. PMID: 17920012.\u003c/li\u003e\n \u003cli\u003eShalev A, Cho D, Marmar CR. Neurobiology and Treatment of Posttraumatic Stress Disorder. Am J Psychiatry. 2024 Aug 1;181(8):705-719. doi: 10.1176/appi.ajp.20240536. PMID: 39086292.\u003c/li\u003e\n \u003cli\u003eKoenen KC, Ratanatharathorn A, Ng L, McLaughlin KA, Bromet EJ, Stein DJ, Karam EG, Meron Ruscio A, Benjet C, Scott K, Atwoli L, Petukhova M, Lim CCW, Aguilar-Gaxiola S, Al-Hamzawi A, Alonso J, Bunting B, Ciutan M, de Girolamo G, Degenhardt L, Gureje O, Haro JM, Huang Y, Kawakami N, Lee S, Navarro-Mateu F, Pennell BE, Piazza M, Sampson N, Ten Have M, Torres Y, Viana MC, Williams D, Xavier M, Kessler RC. Posttraumatic stress disorder in the World Mental Health Surveys. Psychol Med. 2017 Oct;47(13):2260-2274. doi: 10.1017/S0033291717000708. Epub 2017 Apr 7. PMID: 28385165; PMCID: PMC6034513.\u003c/li\u003e\n \u003cli\u003eNasca C, Zelli D, Bigio B, Piccinin S, Scaccianoce S, Nistic\u0026ograve; R, McEwen BS. Stress dynamically regulates behavior and glutamatergic gene expression in hippocampus by opening a window of epigenetic plasticity. Proc Natl Acad Sci U S A. 2015 Dec 1;112(48):14960-5. doi: 10.1073/pnas.1516016112. Epub 2015 Nov 16. PMID: 26627246; PMCID: PMC4672825.\u003c/li\u003e\n \u003cli\u003eWang F, Li Z, Li B, Xu M, Wang Y, Wang J, Li J, Zhu Y, He L, Ma J, Mao L, Xu X, Li X, Zhang H, Yang J, Zhang K, Wu C. Xiaochaihutang ameliorates depression-like behaviors induced via chronic social defeat stress by regulating exon-specific Bdnf transcription through H3K18 acetylation in the hippocampus of mice. Phytomedicine. 2025 May;140:156567. doi: 10.1016/j.phymed.2025.156567. Epub 2025 Mar 3. PMID: 40068295.\u003c/li\u003e\n \u003cli\u003eRoth TL, Zoladz PR, Sweatt JD, Diamond DM. Epigenetic modification of hippocampal Bdnf DNA in adult rats in an animal model of post-traumatic stress disorder. J Psychiatr Res. 2011 Jul;45(7):919-26. doi: 10.1016/j.jpsychires.2011.01.013. Epub 2011 Feb 9. PMID: 21306736; PMCID: PMC3335738.\u003c/li\u003e\n \u003cli\u003eFungaro Rissatti L, Wilson D, Palace-Berl F, de Mello Ponteciano B, Sardela de Miranda F, Alece Arantes Moreno I, Dos Santos Vieira T, Pereira Sorroche B, Rebolho Batista Arantes LM, Madeira Alvares da Silva A, D\u0026apos;Almeida V, Demarzo M, Rodrigues de Oliveira D. BDNF methylation associated with stress in women: Novel insights in epigenetics and inflammation. Brain Behav Immun Health. 2024 Oct 31;42:100900. doi: 10.1016/j.bbih.2024.100900. PMID: 39552782; PMCID: PMC11565430.\u003c/li\u003e\n \u003cli\u003eKim TY, Kim SJ, Chung HG, Choi JH, Kim SH, Kang JI. Epigenetic alterations of the BDNF gene in combat-related post-traumatic stress disorder. Acta Psychiatr Scand. 2017 Feb;135(2):170-179. doi: 10.1111/acps.12675. Epub 2016 Nov 25. PMID: 27886370.\u003c/li\u003e\n \u003cli\u003eTseilikman VE, Tseilikman OB, Pashkov AA, Ivleva IS, Karpenko MN, Shatilov VA, Zhukov MS, Fedotova JO, Kondashevskaya MV, Downey HF, Manukhina EB. Mechanisms of Susceptibility and Resilience to PTSD: Role of Dopamine Metabolism and BDNF Expression in the Hippocampus. Int J Mol Sci. 2022 Nov 23;23(23):14575. doi: 10.3390/ijms232314575. PMID: 36498900; PMCID: PMC9737079.\u003c/li\u003e\n \u003cli\u003eAlahmad R, Hinchey LM, Shaikh M, Amirsadri A, Javanbakht A. Gene expression and epigenetic changes in post-traumatic stress disorder, depression, and anxiety in first responders: A systematic review. J Psychiatr Res. 2025 Feb;182:438-451. doi: 10.1016/j.jpsychires.2025.01.032. Epub 2025 Jan 23. PMID: 39892213.\u003c/li\u003e\n \u003cli\u003eGolubeva E, Zeltser A, Zorkina Y, Ochneva A, Tsurina A, Andreyuk D, Kostyuk G, Morozova A. Epigenetic Alterations in Post-Traumatic Stress Disorder: Comprehensive Review of Molecular Markers. Complex Psychiatry. 2024 Nov 18;10(1-4):71-107. doi: 10.1159/000541822. PMID: 39564465; PMCID: PMC11573359.\u003c/li\u003e\n \u003cli\u003eLipov EG, Candido K, Ritchie EC. Possible Reversal of PTSD-Related DNA Methylation by Sympathetic Blockade. J Mol Neurosci. 2017 May;62(1):67-72. doi: 10.1007/s12031-017-0911-3. Epub 2017 Mar 31. PMID: 28364364.\u003c/li\u003e\n \u003cli\u003eVeltri A, Nicol\u0026igrave; V, Marino R, Rea F, Corsi M, Chiumiento M, Giangreco M, Caldi F, Guglielmi G, Foddis R, Copped\u0026egrave; F, Silvestri R, Buselli R. Plasma Brain-Derived Neurotrophic Factor (BDNF) Levels and BDNF Promoters\u0026apos; DNA Methylation in Workers Exposed to Occupational Stress and Suffering from Psychiatric Disorders. Brain Sci. 2024 Oct 30;14(11):1106. doi: 10.3390/brainsci14111106. PMID: 39595869; PMCID: PMC11592044.\u003c/li\u003e\n \u003cli\u003eKim TY, Kim SJ, Chung HG, Choi JH, Kim SH, Kang JI. Epigenetic alterations of the BDNF gene in combat-related post-traumatic stress disorder. Acta Psychiatr Scand. 2017;135(2):170-179. doi: 10.1111/acps.12675. PMID: 27886370.\u003c/li\u003e\n \u003cli\u003eLee HS, Kwon A, Lee SH. Oxytocin receptor genes moderate BDNF epigenetic methylation by childhood trauma. J Affect Disord. 2022;306:167-173. doi: 10.1016/j.jad.2022.03.020. PMID: 35314247.\u003c/li\u003e\n \u003cli\u003eGuo JC, Yang YJ, Zheng XA, Jiang XL, Guo M, Wang XD, et al. CpG methylation of brain-derived neurotrophic factor gene promoter as a potent diagnostic and prognostic biomarker for post-traumatic stress disorder. Int J Clin Exp Pathol. 2018;11(10):5101-5109. PMID: 31949588; PMCID: PMC6962936.\u003c/li\u003e\n \u003cli\u003eHossack MR, Reid MW, Aden JK, Gibbons T, Noe JC, Willis AM. Adverse Childhood Experience, Genes, and PTSD Risk in Soldiers: A Methylation Study. Mil Med. 2020;185(3-4):377-384. doi: 10.1093/milmed/usz292. PMID: 32976583.\u003c/li\u003e\n \u003cli\u003eRoth, T. L., Matt, S., Chen, K., \u0026amp; Blaze, J. (2014). Bdnf DNA methylation modifications in the hippocampus and amygdala of male and female rats exposed to different caregiving environments outside the homecage. Developmental Psychobiology, 56(8), 1726-1740. doi: 10.1002/dev.21218. Epub 2014 Apr 21.\u003c/li\u003e\n \u003cli\u003ede la Torre, R., Montero-Marin, J., P\u0026eacute;rez-Caballero, D., et al. (2023). Plasma Brain-Derived Neurotrophic Factor (BDNF) Levels and BDNF Promoters\u0026apos; DNA Methylation in Workers Exposed to Occupational Stress and Suffering from Psychiatric Disorders. International Journal of Environmental Research and Public Health, 20(22), 8215. doi: 10.3390/brainsci14111106. PMID: 39595869; PMCID: PMC11592044.\u003c/li\u003e\n \u003cli\u003eChou PC, Huang YC, Yu S. Mechanisms of Epigenetic Inheritance in Post-Traumatic Stress Disorder. Life (Basel). 2024 Jan 8;14(1):98. doi: 10.3390/life14010098. PMID: 38255713; PMCID: PMC10817356.\u003c/li\u003e\n \u003cli\u003eNibuya M, Morinobu S, Duman RS. Regulation of BDNF and trkB mRNA in rat brain by chronic electroconvulsive seizure and antidepressant drug treatments. J Neurosci. 1995 Nov;15(11):7539-47. doi: 10.1523/JNEUROSCI.15-11-07539.1995. PMID: 7472505; PMCID: PMC6578063.\u003c/li\u003e\n \u003cli\u003eShao SH, Shi SS, Li ZL, Zhao MS, Xie SY, Pan F. Aging effects on the BDNF mRNA and TrkB mRNA expression of the hippocampus in different durations of stress. Chin J Physiol. 2010 Oct 31;53(5):285-93. doi: 10.4077/cjp.2010.amk056. Erratum in: Chin J Physiol. 2010 Dec 31;53(6):472. PMID: 21793339.\u003c/li\u003e\n \u003cli\u003ePark C, Rosenblat JD, Brietzke E, Pan Z, Lee Y, Cao B, Zuckerman H, Kalantarova A, McIntyre RS. Stress, epigenetics and depression: A systematic review. Neurosci Biobehav Rev. 2019 Jul;102:139-152. doi: 10.1016/j.neubiorev.2019.04.010. Epub 2019 Apr 18. PMID: 31005627.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"PTSD, BDNF, DNA methylation, epigenetics, meta-analysis, biomarker, promoter IV","lastPublishedDoi":"10.21203/rs.3.rs-8497887/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8497887/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eAlthough there is conflicting quantitative data, the pathophysiology of post-traumatic stress disorder (PTSD) has been linked to epigenetic modification of brain-derived neurotrophic factor (BDNF). For making clear how BDNF promoter DNA methylation relate to PTSD, we did this first meta-analysis.\u003c/p\u003e \u003cp\u003eMethods: Four case-control studies (617 PTSD patients and 518 controls) published before December 2025 was found from PubMed, Web of Science, CNKI, and Wanfang. Using RevMan 5.4 to do sensitivity analyses, subgroup analyses (promoter I vs. IV), and random-effects meta-analyses. The Newcastle\u0026mdash;Ottawa Scale (NOS) was applied for assessing the quality of methods.\u003c/p\u003e \u003cp\u003eResults: Pooled BDNF methylation was significantly lower in PTSD than in controls (SMD = \u0026minus;\u0026thinsp;3.45, 95%CI(-4.45,-2.45), P\u0026lt;0.01), but heterogeneity was high. Subgroup analyses revealed a robust hypomethylation signal for promoter IV, whereas promoter I data showed opposite directional effects and substantial inter-study variance; the combined promoter-I estimate crossed the null line. Sensitivity analyses\u0026mdash;alternating effect models, excluding the largest study, and leave-one-out iterations\u0026mdash;yielded consistent P\u0026thinsp;\u0026lt;\u0026thinsp;0.05, indicating a stable overall effect. Funnel-plot asymmetry suggested possible publication bias.\u003c/p\u003e \u003cp\u003eConclusions: The potential of BDNF promoter IV hypomethylation as a peripheral epigenetic biomarker is supported by its continuous association with human PTSD. But for promoter-I part, the findings still not so clear and need bigger studies with proper medicine control to make sure.\u003c/p\u003e","manuscriptTitle":"Association Between BDNF DNA Methylation and PTSD: A Systematic Meta-Analysis of Human Case–Control Studies","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-01-13 10:22:12","doi":"10.21203/rs.3.rs-8497887/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"4c702357-a3d7-4467-aa6c-27cce97d9055","owner":[],"postedDate":"January 13th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-04-27T03:24:47+00:00","versionOfRecord":[],"versionCreatedAt":"2026-01-13 10:22:12","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8497887","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8497887","identity":"rs-8497887","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}