RESIDUAL NEUROCOGNITIVE FEATURES OF ECSTASY USE: A RE‐INTERPRETATION OF HALPERN ET AL . (2011) CONSISTENT WITH SEROTONERGIC NEUROTOXICITY

Halpern et al. [1] presented some interesting findings from a study of abstinent ecstasy users in Salt Lake City, USA. Their ecstasy group reported comparatively slight use of all psychoactive drugs, both legal and illicit, and were therefore different from the typical user who often takes a range of other drugs. Their control group comprised similar-aged occasional rave attendees, who had never taken ecstasy/3,4-methylenedioxymethamphetamine (MDMA) but had some slight use of other drugs. Halpern et al. [1] reported that ‘we failed to demonstrate marked residual cognitive effects in ecstasy users’, and in their Discussion they suggested that their findings ‘might instead reflect correctly that illicit ecstasy use, by itself, does not generally produce lasting residual neurotoxicity’. I would like to present a rather different interpretation of their findings, as I believe that their data are consistent with current knowledge about the adverse cognitive effects of MDMA and its neurotoxic properties. First, it should be noted that a number of previous studies have also found comparatively slight neurocognitive changes. In a comprehensive meta-analysis of the ecstasy and cognition literature, Rogers et al. [2] noted marked variation across studies. One of the tasks used by Halpern et al. [1] was digit span, and in the meta-analysis by Rogers et al. [2] their Figure 16 revealed a mixture of non-significant and significant changes, although the pooled data showed a significant overall impairment for ecstasy users compared to polydrug controls (P = 0.017). This same pattern emerged with many of the other cognitive tasks. For instance, with the composite index for verbal memory immediate recall (Fig. 21), several studies showed similar group means, others showed moderate significant impairments, while some showed more pronounced deficits. The pooled findings from the 27 published studies again showed a significant overall impairment, in comparison with polydrug control (P < 0.001). Rogers et al. [2] conducted a meta-analysis on seven dependent variables, and six of these showed significant deficits for ecstasy-exposed individuals: Rey Auditory Verbal Learning Test (RAVLT) immediate word recall, RAVLT delayed word recall, Rivermead Behavioural Memory Test (RBMT) immediate prose recall, RBMT delayed prose recall, digit span forwards and digit span backwards. The only measure where ecstasy users did not differ from controls was the National Adult Reading Test Intelligence Quotient (NART IQ) index, showing that the groups did not differ in basic intelligence (Table 4 in their reference 2). So what is causing this variance in findings; why have some studies found cognitive deficits whereas others have not? This was the key issue I addressed in an earlier MDMA review paper [3]. In the introduction I noted that: