On August 27, 2013, the Journal of Psychopharmocology published a Letter to the Editor arguing that our completed Swiss study of MDMA-assisted psychotherapy for PTSD had a large effect size not previously reported in the January 2013 publication of the results in the same journal. In the unsolicited yet most welcome letter, “MDMA-assisted psychotherapy found to have a large effect for post-traumatic stress disorder,” researcher Henri Chabrol of the University of Toulouse, France, explains why our traditional statistical method should have been supplemented by an effect size calculation, and that in fact subjects showed “on average, a substantial improvement in PTSD symptoms over the course of MDMA-assisted psychotherapy.” Receiving this unsolicited positive feedback on our results from an independent expert highlights both the importance of international collaboration in psychedelic research and the sincere caution with which we report our results. View the letter | Download the original paper
