Smoked Cannabis Effects in Cannabis Users at Clinical High-Risk for Psychosis: A Further Investigation of Cognition and Reward

Cannabis acutely worsened cognitive control and produced more aversive intoxication in cannabis users at clinical high-risk for psychosis, but not in psychiatrically-healthy cannabis users. Six high-risk and six healthy users smoked either active (5.5% THC) or placebo cannabis under double-blind conditions. High-risk participants showed decreased response inhibition and aversive intoxication after active cannabis, along with changes in psychomotor speed and cannabis-related attentional bias. No such effects appeared in healthy users. The findings provide preliminary evidence of a deleterious cognitive and reward-related response to cannabis in individuals with preexisting psychosis risk.

Study at a glance

Abstract

Objective. Some adverse cannabis effects are greater in individuals on the psychosis spectrum compared to healthy individuals. We have previously reported that smoked cannabis acutely worsened psychotic-like states and reduced cognitive performance selectively in cannabis users at clinical high-risk (CHR) for psychosis. The objective of the present study was to further investigate the acute effects of cannabis on cognition and reward processing in CHR cannabis users. Method. Six CHR cannabis users and six psychiatrically-healthy cannabis users comparable in intellectual, demographic, and cannabis use characteristics (including nontreatment-seeking status), participated in the study. Objective and subjective measures of cognition and cannabis reward, were completed before and after smoking half of an active (5.5% Δ9tetrahydrocannabinol [Δ9-THC]) or half of a placebo (0.0% Δ9-THC) cannabis cigarette, under randomized/double-blind conditions. Repeated measures ANOVA tested main effects of drug condition (active vs. placebo) and/or the drug condition × time (baseline vs. post-administration) interactions; groups were analyzed separately due to the small sample size. Results. CHR participants exhibited evidence of decreased objective response inhibition and aversive intoxication following active cannabis, relative to placebo. Psychomotor speed and cannabis-related attentional bias were also affected by cannabis intoxication. No such effects were observed in psychiatrically-healthy cannabis users. Conclusion. These findings provide further preliminary evidence of a deleterious cognitive and reward-related response to cannabis in individuals with preexisting risk for psychosis.