MDMA (ecstasy) slows the ability to perceive angry facial expressions, heightens physiological responses to happy expressions, and increases the use of positive words and perceptions of empathy and regard during social interactions. In a double-blind study with 36 healthy volunteers who had previously used ecstasy, doses of 0.75 and 1.5 mg/kg produced these prosocial effects, which were not strongly linked to participants' desire to take the drug again. The findings suggest MDMA alters basic emotional processing by dampening negative emotion recognition and amplifying positive responses, which may contribute to its therapeutic value in psychotherapy but appears less related to its abuse potential.
Low doses of LSD (13 and 26 micrograms) produced broad reductions in brain wave power across multiple frequency bands during rest and dampened specific event-related potentials (P300 and N170) during a visual task in healthy adults. The drug also increased positive mood, energy, and anxiety, as well as heart rate and blood pressure, but did not cause the full perceptual or sensory changes typical of higher psychedelic doses. These neurophysiological effects resemble those seen with higher doses, suggesting that very low LSD doses might produce subtle behavioral or therapeutic effects without inducing a full psychedelic experience.