In a randomized controlled trial, chance decides who gets the treatment and who gets the comparison. Randomizing spreads differences between people, known and unknown, evenly across the groups, so a difference in outcomes is more likely to come from the treatment. Groups are often also blinded so that no one knows who got what (ClinicalTrials.gov).
The comparison varies, and it changes what a result means. Psilocybin depression trials have used a waiting list (Davis et al., 2021), a daily antidepressant (Carhart-Harris et al., 2021), a very low dose (Goodwin et al., 2022) and niacin as an active placebo (Raison et al., 2023). Against escitalopram, the primary result was not significantly different (Carhart-Harris et al., 2021).
Randomization doesn’t fix everything. Small samples, short follow-up and functional unblinding limit what psychedelic trials can show (Muthukumaraswamy et al., 2021). In Canada, a drug trial needs Health Canada’s review of a clinical trial application and approval from a research ethics board (Health Canada).
Sources
- ClinicalTrials.gov: Learn About Studies
- Carhart-Harris et al., NEJM, 2021
- Muthukumaraswamy et al., 2021
- Health Canada: Clinical trials and drug safety
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