Legalization of Psychedelic Substances

The Canadian Network for Mood and Anxiety Treatments (CANMAT) Task Force Report: Serotonergic Psychedelic Treatments for Major Depressive Disorder

OBJECTIVE

Serotonergic psychedelics are re-emerging as potential novel treatments for several psychiatric disorders including major depressive disorder. The Canadian Network for Mood and Anxiety Treatments (CANMAT) convened a task force to review the evidence and provide a consensus recommendation for the clinical use of psychedelic treatments for major depressive disorder.

METHODS

A systematic review was conducted to identify contemporary clinical trials of serotonergic psychedelics for the treatment of major depressive disorder and cancer-related depression. Studies published between January 1990 and July 2021 were identified using combinations of search terms, inspection of bibliographies and review of other psychedelic reviews and consensus statements. The levels of evidence for efficacy were graded according to the Canadian Network for Mood and Anxiety Treatments criteria.

RESULTS

Only psilocybin and ayahuasca have contemporary clinical trials evaluating antidepressant effects. Two pilot studies showed preliminary positive effects of single-dose ayahuasca for treatment-resistant depression (Level 3 evidence). Small randomized controlled trials of psilocybin combined with psychotherapy showed superiority to waitlist controls and comparable efficacy and safety to an active comparator (escitalopram with supportive psychotherapy) in major depressive disorder, with additional randomized controlled trials showing efficacy specifically in cancer-related depression (Level 3 evidence). There was only one open-label trial of psilocybin in treatment-resistant unipolar depression (Level 4 evidence). Small sample sizes and functional unblinding were major limitations in all studies. Adverse events associated with psychedelics, including psychological (e.g., psychotomimetic effects) and physical (e.g., nausea, emesis and headaches) effects, were generally transient.

CONCLUSIONS

There is currently only low-level evidence to support the efficacy and safety of psychedelics for major depressive disorder. In Canada, as of 2022, psilocybin remains an experimental option that is only available through clinical trials or the special access program. As such, Canadian Network for Mood and Anxiety Treatments considers psilocybin an experimental treatment and recommends its use primarily within clinical trials, or, less commonly, through the special access program in rare, special circumstances.

Novel ethical and policy issues in psychiatric uses of psychedelic substances

Classic psychedelics and related substances have shown promising initial research results. However, they raise a number of relatively novel ethical and policy challenges in light of their psychoactive properties, their emergence from the unregulated "underground" settings in which they have been used, their rapid commercialization, and the means and speed with which they are moving from a Schedule 1 drug to legalized use. All of these issues are affected by the current limits to the evidence base on use of psychedelics. Here we survey these novel challenges, illustrating the issues raised regarding each, and offering suggestions for how to address them. Emerging findings on psychedelic therapies suggest promise in treating psychiatric disorders, including major depressive disorder with psilocybin (Carhart-Harris et al., 2021; Compass pathways, 2021; Davis et al., 2021) and post-traumatic stress disorder (PTSD) with 3,4-methylenedioxymethamphetamine (MDMA) (Mitchell et al., 2021). Additional research is underway on other conditions (Reiff et al., 2020). At this early stage in the research process, the published evidence supporting psychedelic use is limited by relatively small sample sizes (as compared to Phase 3 trials for conventional anti-depressants), highly selected and perhaps atypical participants, and the need for replication (Smith and Appelbaum, 2021b). Nevertheless, the promise of these findings and the emerging efforts at legalization and/or decriminalization in several parts of the country, utilizing a diversity of mechanisms, raise important ethical and policy questions that have received little systematic exploration. To help address this deficit, this commentary surveys four domains in which ethical and policy questions arise. We focus chiefly on psilocybin, the most promising of the psychedelics now being investigated, though our conclusions may generalize to other classic psychedelics or related agents, like MDMA. Of note, we focus here on questions that are relatively novel or particularly important for psychedelics. Many other ethical issues regarding psychedelics in both research and clinical contexts will be similar to those for other treatment modalities. As with other modalities, when used in clinical practice there will be ethical challenges regarding patient confidentiality, informed consent, balancing the risks and benefits of treatment, and provision of equitable access. Clinical research on psychedelic compounds is not unusual in raising concerns about the adequacy of understanding of randomization and possibility of allocation to the control arm of the trial, therapeutic misconception, and exclusion or exploitation of marginalized or otherwise disadvantaged groups (Emanuel et al., 2000). Regarding disadvantaged groups, like many other areas of medical research, early psychedelic research had a significant history of exploitation of vulnerable populations including imprisoned persons and people of color (Strauss et al., 2021). Although we acknowledge the importance of issues that are very similar to those for other treatment modalities, we do not discuss them in detail.