A systematic review and meta-analysis of seven randomized trials involving 436 adults with clinically significant depression found that psilocybin produced a moderate-to-large reduction in depression symptoms compared with placebo or non-psychoactive comparators (Hedges' g = 0.66). Greater improvements were linked to secondary depression, use of self-report scales, older age, and prior psychedelic use. All studies had moderate risk of bias, but the evidence was rated as moderate certainty. The authors conclude that further research is needed to clarify expectancy effects, moderating factors, and treatment delivery.
New Zealand clinicians developed practical guidelines for using ketamine to treat treatment-resistant major depressive disorder in publicly funded specialist mental health services. The guidelines offer two treatment pathways: a test of responsiveness with intramuscular ketamine followed by a 3-month course of oral ketamine, aiming to maximize short-term benefits. The guidance was created through consultation with senior leadership, clinical pharmacy, psychiatrists, nursing, service users, and Māori mental health workers.