Have Halpern et al. (2004) detected 'residual neuropsychological effects' of MDMA? Not likely

[Extract] The preliminary study by Halpern et al. (2004) is a commendable attempt to isolate correlates of ‘Ecstasy’ use from some of the many confounds that have plagued previous work on this controversial issue. However, Halpern et al. go far beyond their data by concluding that the few significant differences they found, out of a great number of comparisons conducted on a small sample of subjects, actually represent ‘residual neuropsychological effects of MDMA.’ Indeed, as their findings fail to establish a cause–effect relationship between heavy MDMA use and neurocognitive impairment, their use of the term ‘residual effect’ is very misleading.