Combining MDMA and THC does not worsen cognitive impairment beyond that caused by THC alone, but it does increase the desired subjective drug effects and perceived drug strength, which may explain why many young people use them together. In a placebo-controlled crossover trial with 16 healthy volunteers aged 18–27, THC alone produced more robust cognitive impairment than MDMA alone, and co-administration did not exacerbate single-drug effects on cognitive function. However, the combination enhanced subjective experiences compared with MDMA alone.
The pharmacokinetic parameters of psilocin are consistent across different studies. This finding may help guide the further clinical development of psilocybin-based therapies.