Research hasn’t definitively answered whether MDMA is addictive, although it affects many of the same neurotransmitter systems in the brain that are targeted by other addictive drugs. Experiments have shown that animals will self-administer MDMA—an important indicator of a drug’s addictive potential—although the degree of self-administration is less than some other addictive drugs, such as cocaine.114,115

Data from both humans and animals suggest that regular MDMA use produces adaptations in the serotonin and dopamine systems that are associated with substance use disorder and related behaviors, such as increased impulsivity.116 Few studies have attempted to assess MDMA addiction or dependency among people with a history of use in the general population. Studies that have been conducted have shown widely varying results, likely because of the different population samples and different types of measures used. Some people who use MDMA do report symptoms of addiction, including continued use despite negative physical or psychological consequences, tolerance, withdrawal,117,118 and craving.119