Microstructural Brain Abnormalities in HIV+ Individuals with or without Chronic Marijuana Use

Abstract Objective Cognitive deficits and microstructural brain abnormalities are well documented in HIV-positive individuals (HIV+). This study evaluated whether chronic marijuana (MJ) use contributes to additional cognitive deficits or brain microstructural abnormalities that may reflect neuroinflammation or neuronal injury in HIV+. Method: Using a 2 × 2 design, 44 HIV + participants, [23 minimal/no MJ users (HIV+), 21 chronic active MJ users (HIV + MJ)], were compared to 46 seronegative participants [24 minimal/no MJ users (SN) and 22 chronic MJ users (SN + MJ)] on neuropsychological performance (7 cognitive domains) and diffusion tensor imaging metrics, using an automated atlas to assess fractional anisotropy (FA), axial (AD), radial (RD), and mean (MD) diffusivities, in 18 cortical and 4 subcortical brain regions, Results Compared to SN and regardless of MJ use, the HIV + group had lower FA and higher diffusivities in multiple white matter and subcortical structures (p = 0.001–0.050), as well as poorer cognition in Fluency (p = 0.039), Attention / Working Memory (p = 0.009), Learning (p = 0.015) and Memory (p = 0.028). Regardless of HIV-serostatus, MJ users had lower AD in uncinate fasciculus (p = 0.016) but similar cognition as non-users. No additive or interactive effects were found between HIV-serostatus and MJ use on DTI metrics or cognitive function. Furthermore, higher MD in thalamus predicted poorer fluency, learning and memory in HIV + participants, while higher RD in posterior corona radiata predicted poorer learning in MJ users. Lower FA in the anterior internal capsule also predicted worse attention/working memory in all except SN subjects. Lastly, MJ users with or without HIV-infection showed greater than normal age-dependent FA declines in superior longitudinal fasciculus, external capsule and globus pallidus.