Specific memory deficits in ecstasy users? The results of a meta-analysis.

A meta-analysis was carried out on the possible functional neurotoxic effects of ecstasy use in humans on verbal short-term memory (STM), verbal long-term memory (LTM), processing speed (RT) and % errors (attention). To that end studies were found on the effect of ecstasy that fulfilled the criteria for a meta-analysis (number of subjects, means and standard deviations of the dependent variables). Ten studies were included on STM, ten on LTM, eight on RT and eight on % errors (attention). In addition meta-regression analyses were carried out on the effect sizes with total lifetime ecstasy consumption (TLEC) as predictor. It was found that in all four meta-analyses the mean effect size (ES) was significant: ecstasy users had lower verbal STM and LTM scores, reacted slower and made more errors. The meta-regression coefficients were not significant, indicating no support for a linear relationship between the mean ES values and TLEC, leaving open the possibility for a stepwise relationship. Additional meta-analyses on ecstasy groups that did not differ in lifetime cannabis consumption showed that only the ES for LTM became insignificant. This suggests that ecstasy use does not decrease LTM, but the number of studies on which this conclusion is based was very low. Copyright 2003 John Wiley & Sons, Ltd.