Microstructural brain abnormalities in HIV+ individuals with or without chronic marijuana use.

Area of Science:

• Neuroscience
• Neurology
• Infectious Diseases

Background:

• HIV infection is associated with cognitive deficits and brain microstructural abnormalities.
• Chronic marijuana use is prevalent among individuals with HIV, raising concerns about potential additive neurotoxic effects.

Purpose of the Study:

• To investigate whether chronic marijuana use exacerbates cognitive deficits or brain microstructural abnormalities in HIV-positive individuals.
• To assess the impact of marijuana use on neuroinflammation and neuronal injury in the context of HIV infection.

Main Methods:

• A 2x2 design compared HIV-positive (HIV+) and seronegative (SN) participants, with subgroups of minimal/no marijuana (MJ) users and chronic active MJ users.
• Neuropsychological performance across seven cognitive domains and diffusion tensor imaging (DTI) metrics (FA, AD, RD, MD) were assessed in 18 cortical and 4 subcortical brain regions.
• Automated atlas-based analysis was employed for DTI metrics.

Main Results:

• HIV+ individuals exhibited lower fractional anisotropy (FA) and higher diffusivities in white matter and subcortical regions, alongside poorer performance in fluency, attention/working memory, learning, and memory, irrespective of MJ use.
• Chronic MJ users showed lower axial diffusivity (AD) in the uncinate fasciculus, but comparable cognitive function to non-users.
• An interaction effect between HIV status and MJ use was observed on mean diffusivity (MD) in the right globus pallidus, but not on cognitive function. Lower FA and higher diffusivities predicted poorer cognitive outcomes.
• MJ users, with or without HIV, demonstrated accelerated age-dependent FA declines in specific white matter tracts and the globus pallidus.

Conclusions:

• Chronic marijuana use generally does not impose additional neurocognitive or microstructural burdens on HIV-positive individuals, with the exception of the globus pallidus.
• Reduced AD in the uncinate fasciculus among MJ users suggests potential axonal loss, impacting regions involved in verbal memory and emotion.
• Accelerated age-dependent FA declines in MJ users indicate a potential for reduced neuronal integrity in specific brain regions with aging.