3. Psychedelics in psychiatry: focus on evidence and mechanisms of relevance to affective disorders and addictions

After a decades-long global arrest of research on psychedelic drugs, investigations into psychedelic-assisted therapies have recently provided promising results for a range of serious psychiatric conditions, including major depression and tobacco and alcohol addictions.

In a double-blind, randomized, controlled major depression trial we compared 6 weeks of daily escitalopram (a selective serotonin reuptake inhibitor, or SSRI) with 2 treatment sessions (3 weeks apart) with the classic tryptamine psychedelic, psilocybin.

Overall, symptom severity generally favoured psilocybin over escitalopram when assessed at week 6 (Carhart-Harris et al 2021, NEJM). However, neither long-term follow-up depression severity data, treatment expectation effects or effects of being tapered off antidepressant medication prior to start of treatment in this trail were addressed in the original publication. The data will be presented together with evidence and models related to possible brain mechanisms of psychedelic action.

The presentation will aim to highlight mechanisms of relevance to both affective disorders and addictions. Funding: Work presented was supported by a private donation from the Alexander Mosley Charitable Trust and by the founding partners of Imperial College London’s Centre for Psychedelic Research. Infrastructure support was provided by the NIHR Imperial Biomedical Research Centre and the NIHR Imperial Clinical Research Facility.