| Summary: | Rationale - MDMA is currently an illegally abused recreational drug. Non-human animal studies demonstrate that MDMA causes non-repairable damage to serotonergic neurons. As the acute behavioural effects of MDMA are similar between non-human animals and humans, it is plausible to suggest that the neurotoxic effects of MDMA will be the same in each group. Results from previous human research investigating the psycho biological effects of MDMA have been inconsistent. They have relied on limited sample sizes and lack adequate control groups. The overall aim of the present study was to examine behaviours associated with 5- HT including: sleep, depression, impulsivity, memory, and executive functioning. The study investigated 5- HT related behaviours comparing past and present polydrug MDMA users whilst controlling for other recreational drugs. Method - The study involved a total of 1399 participants split across 6 groups: non-drug control; nicotine/alcohol control; nicotine/alcohol/cannabis control; non-MDMA polydrug control; current MDMA polydrug and past MDMA polydrug. Participants were required to complete the following: demographic and drug history questionnaire, Becks Depression Inventory (Version II), Pittsburgh Sleep Scale, Barratt Impulsivity Questionnaire, Wechsler Memory Test (Revised), Wisconsin Card Sorting Test, and the Tower of London Test. Results - The study found that past and present MDMA users suffer from specific deficits in measures of depression (cognitive-affective subscale), sleep, impulsivity (attention and motor subscales) and memory (verbal, visual, delayed). Past and present MDMA users displayed problems in selected executive functions: planning; solution time; and number of errors. Interestingly, statistical regression analysis predicted that these deficits in executive functioning may be due to MDMA, (1) directly affecting other psychological processes: memory, impulsivity, and sleep, which indirectly affects performance on executive functions; or, (2) MDMA directly disrupts executive functions: planning, solution time, and number of errors. Discussion - The present study is the first and largest study to date to suggest that MDMA causes acute and long lasting changes to specific psychological functioning: depression, sleep, impulsivity, memory, and executive functioning; without recovery even after 5 years of abstinence. Future studies need to control for mood, sleep disturbance, memory deficits, and elevated impulsivity when investigating disruptions to executive functions in past and present polydrug MDMA users.
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