Reasoning deficits in ecstasy (MDMA) polydrug users

Rationale/objectives: Previous research has shown that ecstasy users are impaired in thinking and reasoning. The present study sought to explore the possibility that syllogistic reasoning errors in ecstasy users were due to an inability to construct a model of the premises due to working memory limitations. Methods: Twenty-nine ecstasy users and 25 nonecstasy user controls completed abstract syllogistic reasoning problems varying in difficulty. Pairs of premises were provided, and participants were required to generate conclusions that followed necessarily from them. Results: On the easier problems, both groups performed at well above chance although nonusers achieved significantly more correct responses. Consistent with existing research, on the more difficult problems, errors by nonusers were characterised by incorrect conclusions suggesting that while nonusers have the working memory capacity to construct a single model of the premises, this is not an exhaustive representation and usually results in an erroneous conclusion. On the other hand, for all problem types, ecstasy users, rather than produce incorrect responses, were more likely to fail to generate a conclusion. Conclusions: The present results are consistent with the possibility that ecstasy users with their reduced working memory capacity may experience difficulty in constructing even a single model of the premises. While this might be attributable to the effects of 3,4-methlylenedioxymethamphetamine neurotoxicity, many of the ecstasy users in the present study were polydrug users. Thus, the possibility that other drugs including cannabis and cocaine might contribute to the present results cannot be excluded.