MDMA research is a fascinating branch of research medicine that is now really taking off. Dr Pathania refers to the recent work of Mithoefer and colleagues, whose long-term follow-up study showed a sustained absence of PTSD symptoms in 20 patients with treatment-resistant PTSD 4 years after a single course of MDMA-assisted psychotherapy.

In the wake of these pilot studies, MDMA therapy research is now moving into phase 3, with large, multicentre trials beginning within the next 24 months (see www.maps.org/research/mdma for more details). This includes, we hope, a UK-based arm of the project and a planned licensing date for MDMA as a prescription medicine for treatment-resistant PTSD by 2021. These are bold steps indeed. For the large population of patients with PTSD who remain chronically unwell and untreated by traditional methods (almost 50% of all sufferers) this cannot come soon enough.

Drs Nour & Krzanowski provided a thoughtful and stimulating reply to the article I co-authored with Dr Matt Johnson regarding the contemporary development of psychedelic drug-assisted psychotherapy for drug dependence disorders. ^{Reference Sessa and Johnson1} They are absolutely correct to draw attention to the importance of set and setting. These are essential factors to bear in mind whenever a psychedelic drug is used – either clinically, during research or recreationally; the outcome of a psychedelic experience is highly dependent on the user’s mindset and the environmental conditions in which they take the drug. ^{Reference Sessa2} All the research studies Dr Johnson and I mentioned in our review have appropriately paid attention to the concepts of set and setting.

In Dr Johnson’s work within the USA with psilocybin, in all the UK-based psychedelic drug studies that I have contributed towards in recent years (with LSD, ketamine and psilocybin), and in our forthcoming UK-based MDMA study, we have been careful to ensure that participants are fully informed about the drugs they are taking, that appropriate safety measures are in place to reassure them and that the studies are conducted in safe, welcoming, relaxed and facilitative environments. These measures are an important active part of the drug experience. It is arguable that much of the bad press psychedelics have received in the decades since their vilification in the late 1960s has arisen as a result of negative psychedelic experiences in the context of poorly managed set and settings. When these factors are diligently managed, the vast majority of psychedelic experiences in most people are positive. The epidemiological work of Dr Teri Krebs, who looked at a very large sample of psychedelic users, illustrates the relative safety and benefit of psychedelic drug use in contemporary times. ^{Reference Krebs and Johansen3}