In the realm of recreational substances, MDMA, commonly known as 'ecstasy' or 'molly,' has long been used in social settings such as parties and concerts. Users report that the drug enhances their sense of connection and empathy toward others. Even rodents exhibit more prosocial behaviors when given MDMA, such as spending more time laying in close physical contact next to other rats. These effects are believed to be mediated by oxytocin, a neuropeptide released in response to positive social interactions in mammals.

In our recent study, we sought to quantify the effects of MDMA on feelings of connectedness during social interactions in healthy volunteers. We also studied the effects of MDMA to another stimulant drug, methamphetamine, for comparison, to see if the social effects were specific to MDMA. One group of subjects received MDMA or placebo on two sessions, before engaging in a casual conversation with a stranger they had never met before. They met with one partner after MDMA and another conversation partner after placebo, engaging in 45-minute conversations discussing relatively impersonal topics (e.g., favorite holidays or the last concert they attended). The drug was administered under double-blind conditions. After the 5-hour session, participants were asked to rate their feelings toward their conversation partners and the overall quality of the conversations. The results confirmed our hypothesis: participants reported feeling significantly more connected the partner they met after consuming MDMA, compared to partner they met after placebo. MDMA also made the conversations seem more meaningful, both during the session and as long as one week later.

A separate group of participants underwent a similar procedure with methamphetamine (Study 2), a prototypical stimulant which is not widely thought to increase empathy. Surprisingly, we found that methamphetamine also increased feelings of connectedness and enhanced the meaningfulness of conversations, just as MDMA did. We also measured salivary levels of the bonding hormone oxytocin during the sessions. We found that increased levels of oxytocin were related to feelings of closeness after MDMA, but not after methamphetamine.

Our study provides new information about the prosocial effects of MDMA. First, it shows that the drug enhanced feelings of connection and meaningfulness, even when expectancies were minimized with the double-blind procedure. This was the first study to investigate the effect of MDMA during a structured, dyadic conversation. Second, we discovered, to our surprise, that methamphetamine produced a similar effect, even though methamphetamine is not typically known for its effects on empathogenic effects. Third, we found that the increased feelings of closeness were related to drug-induced increases in oxytocin levels after MDMA, but not after methamphetamine. This suggests that different physiological factors might contribute to feelings of closeness. The findings are especially important as MDMA is close to approval for use in therapeutic settings. Prosocial effects such as those reported here may also contribute to the therapeutic effectiveness of MDMA, when combined with psychotherapy. Further studies are needed to replicate and extend these findings to other drugs and doses, other subject samples, and other types of social interactions. Studies of this kind will ultimately help us understand how the drugs produce behavioral effects, in both recreational and clinical settings.