The effects of ecstasy (MDMA) and cannabis use on executive functioning

Background: Random letter generation (RLG) loads upon the inhibition and long-term memory access components of executive functioning. Previous studies from our laboratories have reported contrasting findings regarding deficits on this task in users of ‘ecstasy’. The present study examined users’ RLG performance in both a single and dual task condition, and also investigates the potentially confounding role of cannabis use on performance. Method: Group was a between-participants independent variable at three levels, namely, users of both ecstasy and cannabis (E/C group, n = 12), users of cannabis but not ecstasy (CA group, n = 14), and controls (CO group, n = 15). Task condition was within-participants at two levels (single and dual task, respectively). In the single task condition participants produced 100 letters at a rate of 1 every 2 s. In the dual task condition participants performed a computer generated visuospatial working memory task with random letters being produced with the appearance of each grid. Results: RLG redundancy scores showed significantly poorer performance by the E/C group compared to the CO group. No other inter-group comparisons were significant. Age and a measure of visuospatial working memory as respective covariates made this significant comparison narrowly nonsignificant. No interaction was found between group and task condition. Regression analyses using age, and respective estimates of lifetime ecstasy and cannabis consumption showed only ecstasy consumption to be a significant performance predictor in the single task condition. Conclusions: Ecstasy consumption may contribute to deficits in tasks drawing upon the inhibition component of the working memory executive, although further investigation is needed. Cannabis consumption had a negligible effect on RLG performance. The additional executive demands of the dual task condition were spread evenly across the groups.