Psychedelics in the treatment of unipolar and bipolar depression

Classic psychedelics such as LSD, psilocybin, mescaline, and ayahuasca are being studied again for treating unipolar and bipolar depression. They alter sensory perception, emotion, and self-processing by stimulating serotonin 2A receptors in the brain. Psychedelic-assisted psychotherapy integrates a safe psychedelic experience into ongoing therapy. Early randomized trials with psilocybin show promising results for unipolar depression, but classic psychedelics may also trigger mania. Atypical psychedelics like MDMA and ketamine work through different mechanisms; esketamine is approved for treatment-resistant unipolar depression, and ketamine shows early evidence for bipolar depression. Larger trials and careful legal frameworks will determine their broader clinical use.

Study at a glance

Abstract

Abstract This is a narrative review about the role of classic and two atypical psychedelics in the treatment of unipolar and bipolar depression. Since the 1990s, psychedelics experience a renaissance in biomedical research. The so-called classic psychedelics include lysergic acid diethylamide (LSD), psilocybin, mescaline and ayahuasca. Characteristic effects like alterations in sensory perception, as well as emotion- and self-processing are induced by stimulation of serotonin 2A receptors in cortical areas. The new paradigm of psychedelic-assisted psychotherapy suggests a therapeutic framework in which a safely conducted psychedelic experience is integrated into a continuous psychotherapeutic process. First randomized, controlled trials with psilocybin show promising efficacy, tolerability, and adherence in the treatment of unipolar depression. On the other hand, classic psychedelics seem to be associated with the induction of mania, which is an important issue to consider for the design of research and clinical protocols. So called atypical psychedelics are a heterogeneous group with overlapping subjective effects but different neurobiological mechanisms. Two examples of therapeutic value in psychiatry are 3,4-methyl​enedioxy​methamphetamine (MDMA) and ketamine. Since 2020 the ketamine enantiomer esketamine has been granted international approval for treatment-resistant unipolar depression, and also first evidence exists for the therapeutic efficacy of ketamine in bipolar depression. Whether psychedelics will fulfil current expectations and find their way into broader clinical use will depend on future rigorous clinical trials with larger sample sizes. A well-considered therapeutic and legal framework will be crucial for these substances to create new treatment settings and a potential paradigm shift.