Association of Marijuana Use with Changes in Cognitive Processing Speed and Flexibility for 17 Years in HIV-Seropositive and HIV-Seronegative Men.

Background: The long-term effects of marijuana on cognition, particularly in the context of HIV is not clear, as extant research shows mixed findings.

Objective: To determine associations between current and cumulative exposure to marijuana and changes in cognitive processing speed and flexibility in 788 HIV-seropositive (HIV+) and 1,132 HIV-seronegative (HIV-) men followed for up to 17 years in the Multicenter AIDS Cohort Study.

Results: Among HIV+ men only, current daily marijuana use compared to none-use, was significantly associated with a greater annual percentage decline in cognitive processing speed assessed with the Trail Making Test A (TMTA) (β=-0.41, 95% confidence interval (CI): -0.88, -0.03, p=0.03)] and Symbol Digit Modalities Test (SDMT) (β= -0.14, 95% CI: -0.28, -0.01, p=0.04). Further, monthly marijuana use was associated with greater annual percentage decline in cognitive flexibility assessed with the Trail Making Test B (TMTB) (β= -0.70, 95% CI: -1.34, -0.05; p=0.03] and cognitive processing speed (SDMT) (β= -0.21, 95% CI: -0.40, -0.01, p=0.03). Among the HIV- men only, each 5-marijuana use-years (equivalent to 5-years of daily marijuana use) was significantly associated with a 0.17 annual percentage decline in cognitive processing speed only (TMTA) (β= -0.18, 95% CI: -0.36, -0.01; p=0.04).

Conclusions: Our findings suggest that marijuana use, particularly current use, may be associated with worse cognitive processing speed, but the magnitude of the estimates was not clinically meaningful.