Moderate MDMA use does not cause lasting cognitive impairments beyond those linked to general heavy drug use, but using multiple drugs together may lead to dose-related problems in temporal and frontoparietal brain function. Marijuana use appears especially harmful. The cause-effect relationships remain uncertain.
MDMA, also known as ecstasy, is a selective serotonin neurotoxin in many species and has been linked to memory problems in humans. Recent research indicates that this memory impairment can last for at least a year after stopping use, but it was unclear which stage of memory processing is affected. This study compared 31 current MDMA users, 30 former users who had abstained for over two years, and 30 non-users using the WMS-III memory test. The results suggest MDMA use is associated with memory dysfunction that persists for up to two years after cessation, and that the impairment may stem from interference during the encoding stage of memory processing.
Psilocybin temporarily changes specific cognitive functions in a way that depends on dose and time, affecting localized brain processes rather than overall cognition. The authors note that current research has important methodological limitations, so more studies are needed—especially those using standardized methods, focusing on depression, and tracking effects over longer periods.