The Longitudinal Impact of Cannabis Use On Cognitive Functioning in First Episode Psychosis
Methods: A total of 183 first episode neuroleptic naïve participants with psychosis were recruited through Western Psychiatric Institute and Clinic, Pittsburgh. Participants were enrolled and followed 1-year from their first psychotic episode. Of those enrolled, 41 (22%) used cannabis over the 1-year follow-up period. The computerized version of the Wisconsin Card Sorting Test was used to assess executive functioning (WSCT) at baseline, 6-months and 1-year. Linear growth curve models were used to examine 1-year executive functional outcome trajectories between the cannabis misusing and non-cannabis using participants with psychosis.
Results: The differences in WSCT percent perseverative errors score changes between first episode participants who used cannabis and the non-cannabis users were examined. Over 1-year, the effects of cannabis on cognition in schizophrenia were readily discernible between participant groups. Contrary to our expectations, participants who used cannabis exhibited significantly faster improvement in executive functioning compared to those not using cannabis, F (1, 130) = 4.55, p = .035, comparatively. These results show that the first-episode participants who used cannabis experienced slightly greater improvements in cognitive functioning following their first-episode of psychosis, which may account for cross-sectional studies demonstrating greater cognitive abilities in participants with psychosis who use cannabis.
Conclusions and Implications: The clinical relevance of this research is underscored by the fact that this was the first study to examine the longitudinal effects of cannabis use on cognition in first-episode psychosis. Our sample was clinically homogenous, and presented without the confounding effects of illness chronicity and neuroleptic medications on cognition. Despite our expectations, the use of cannabis was associated with a more rapid decrease in executive impairments after the introduction of antipsychotic medication. This may be due to elevated initial rates or a different pathogenesis of cognitive dysfunction among cannabis users that may be more responsive to traditional pharmacotherapy. The clinical correlates of cannabis have not been thoroughly examined in first-episode psychosis, and it will be important for social work to secure an integral role in future research development efforts.