Executive Working Memory Deficits in Abstinent Ecstasy/MDMA Users: A Critical Review

A review of 33 studies on abstinent ecstasy (MDMA) users found that deficits in executive functioning are most consistently observed for updating verbal information and for visuospatial memory tasks that demand more than simple storage and retrieval, suggesting the overall level of executive demand is important. Evidence for impairment in shifting between mental sets was weak, while findings for inhibition and long-term memory access were unclear. All but one study used a cross-sectional design, a noted limitation, but researchers generally controlled for confounds such as other drug use through group designs and statistics. The review recommends future studies specify which executive processes tasks measure and consider task difficulty.

Study at a glance

Abstract

Aims: This review examined studies of executive functioning in abstinent ecstasy (3,4-methylenedioxymethamphetamine, MDMA) users on tasks which had been empirically mapped onto updating, shifting, inhibition and accessing long-term memory executive processes. Studies of some aspects of visuospatial memory performance were also included because of the investment of executive resources in such tasks. Methods:Thirty-three studies were identified for the review following searches of the Psychinfo and Medline databases. Inclusion criteria were the reporting of new empirical findings from participants drug free at the time of testing, in peer-reviewed journals in the English language. Results:Evidence for ecstasy-related performance deficits was strongest for the updating of verbal material, and for visuospatial memory tasks requiring additional processing beyond storage and retrieval. Such processing suggested that the overall level of executive demand was an important consideration. Executive shifting showed little evidence of ecstasy-related impairment, whilst examination of inhibition and long-term memory access presented an unclear picture. Conclusions: All but one of the studies had a cross-sectional design. Although this is a potential weakness with regard to confounds, the necessity of such designs was acknowledged. Studies were generally aware of the need to control for potential confounds, especially the effects of other drugs, through a mixture of group designs and statistical techniques. It was recommended that future studies of executive functioning in ecstasy users should detail the relationship of the tasks and dependent variables reported to specific executive processes and consider the level of executive demand imposed by such tasks.