Major depressive disorder (MDD) is a clinically defined entity with little understanding as to the underlying pathological substrate. Biologically, MDD is characterized by disruption of neurotransmitters, especially serotonin and noradrenaline, which are the main targets of antidepressants. We previously demonstrated significant reduction of glial cell number in the cingulate and dorsolateral prefrontal cortical regions. Unfortunately, individuals living with HIV still have very high rates of MDD, despite the fact that mortality rates have fallen sharply with effective antiretroviral treatment. It is possible that in this treatment era, living with chronic HIV infection may result in long-term neuropathological changes that predispose to MDD. For example, it is known that HIV is associated with a range of inflammatory pathologies, neuronal loss, and dendrite-synaptic damage. In HIV, these neurodegenerative changes have been linked to neurocognitive impairments, however it is also possible that these changes potentiate MDD.