Marijuana use and cognitive function in HIV-infected people.

The effect of marijuana use on cognitive function is controversial. Although marijuana use is common in HIV-infected individuals for recreational and medicinal purposes, there have been no studies of the impact of marijuana on cognitive function in these subjects. Marijuana also has known immunologic effects, which increases the relevance in HIV-infected patients. We examined the interaction of HIV disease-stage and marijuana use in 282 subjects, stratified by disease stage and frequency of marijuana use. After controlling for the effects of depression, anxiety, and alcohol use, a significant interaction was observed on an overall measure of cognitive impairment. The effect of marijuana use was greatest in subjects with symptomatic HIV infection. Further inspection suggested that this effect was due primarily to performance on memory tasks. These data suggest that although there is minimal impact of marijuana on uninfected individuals or those at early stages of HIV infection, there is a synergistic effect of HIV and marijuana use in patients with advanced HIV disease. This is consistent with other data suggesting that the subtle effects of some conditions may become more manifest in the setting of immunocompromise.