Hair Cortisol as a Predictive Biochemical Indicator for the Preventive and Personalised Evaluation of Suicide Risk in Depression? An Exploratory Comparison Study Between Mentally-Stable Control Subjects, Depressed Individuals and Individuals After Completing Suicide

Abstract Depression and suicidal behaviour are interrelated, stress-associated mental health conditions, each lacking biological verifiability. Concepts of predictive, preventive and personalised medicine (3PM) are almost completely missing for both conditions but are of utmost importance. Research reported altered levels of the stress hormone cortisol in the scalp hair of depressed individuals, while data on hair cortisol concentrations (HCC) for suicide completers (SC) are completely missing. Compared to mentally-stable control subjects (n = 12), we expected chronic stress-associated HCC elevation in depressed patients (n = 20), with an additional HCC increase in SC (n = 45) that might lead to the identification of between-group differences towards a 3PM conceptualization. HCC was measured cross-sectionally in extracts of pulverized hair (1cm and 3cm hair segments) using ELISA. In 3cm hair segments, we found an average increase in HCC for depressed patients (x1.66) and SC (x5.46) compared to controls. Furthermore, the average HCC in SC was significantly increased compared to the depressed group (x3.28). A significant correlation between HCC in the 1cm and the 3cm hair segments, as well as a significant association between HCC (3cm segment) and the severity of depressive symptoms, were also found. We replicate findings of increased HCC in depressed subjects compared to controls. Additionally, we provide data on HCC in SC, showing an additional increase in HCC compared to both controls and depressed patients. The usage of HCC as a predictive/preventive tool in the context of 3PM to possibly indicate and monitor suicidal risk in depression is an urgent question that needs to be answered timely.