MDMA enhances pleasantness of affective touch

A growing body of evidence indicates that ecstasy, or ±3, 4-methylenedioxymethamphetamine (MDMA) produces distinctive pro-social effects. MDMA is a popular recreational drug which purportedly produces feelings of empathy and interpersonal closeness. It has also been used therapeutically, where it enhances treatment for PTSD and social anxiety associated with autism when used in conjunction with psychotherapy [1, 2]. A number of controlled, double-blind studies have examined the behavioral effects of MDMA to identify the psychological and neural processes that underlie these effects, and distinguish it from other stimulant drugs [3–5]. For example, one consistent finding has been that MDMA decreases sensitivity to detecting negative emotions depicted in faces, while improving the ability to detect positive emotions. These two actions could facilitate both positive social interactions with strangers and interactions with a psychotherapist.

To fully understand the profile of social effects of a drug, it is of value to examine its effects on other basic modalities of social communication, aside from perceptions of visual stimuli. One modality that has received little attention is the sense of touch. Anecdotally, recreational MDMA users report that MDMA increases the pleasantness of social touch. In a recent study, we examined the acute effects of MDMA on responses to social, or affective, touch, in healthy young adults, under double blind conditions. Affective touch is touch that is experienced as hedonically pleasant, and has a known sensory pathway through activation of C-tactile afferents in the skin: slow stroking of the skin activates these afferents and is experienced as pleasurable, whereas faster stroking does not, and is not perceived as pleasant. Interestingly, the sensation of affective touch is thought to be mediated by both serotonin and oxytocin, which are also implicated in the behavioral actions of MDMA.

In our study [6], healthy volunteers (N = 36) participants received single doses of MDMA (0.75 or 1.5 mg/kg), 20 mg methamphetamine (MA) or placebo in a double-blind, within-subject design. MA was included as a prototypic stimulant drug, for comparison. At the time of peak drug effect, participants completed a touch task in which they rated the pleasantness (7 point Likert scale) of two different touch stimuli: slow stroking (3 cm/s) and faster stroking (10 cm/s) of the forearm. The touch was conducted with a soft brush rather than a hand to control for variation in skin temperature. Stroking at the slower frequency is known to preferentially activate CT-afferents, and thus is referred to as “affective touch.” As expected, subjects rated the slow, affective, touch as more pleasant than fast touch. Further, and consistent with our expectations, MDMA significantly increased the perceived pleasantness of the slow touch, but not the fast touch. The prototypic stimulant MA produced its typical subjective effects but did not affect either pleasantness or intensity of the touch.

The results advance the field in two ways. First, they demonstrate the pro-social effect of MDMA in a novel modality, the sense of touch. The effect was dose-dependent, specific to MDMA (not MA) and limited to affective touch, compared to touch at other frequencies. Second, our use of the measure of affective touch opens a new door to psychopharmacological research investigating how drugs affect social behavior and perception.

Funding and disclosure

This work was supported by a grant from the National Institute on Drug Abuse (DA02812), and AKB was supported by a training grant from the National Institute of General Medical Sciences (2T32GM007281). We acknowledge our co-authors on the original paper L.M. Mayo, K. Van Hedger, F. McGlone, and S.C. Walker. The authors declare no competing interests.