Antidepressant use is increasing worldwide, especially in high-income countries. However, roughly 30 percent of people taking the drugs are resistant to their effects. A recent systematic review and meta-analysis found that people with depressive symptoms who took psilocybin were two times more likely to respond to treatment than those not taking the drug.

Researchers analyzed the findings of randomized clinical trials that evaluated the effects of psilocybin therapy on depressive symptoms. They included nine studies involving 436 patients in their analysis.

They found that participants taking psilocybin were two times more likely to respond to treatment than those not taking the drug, especially among those with secondary depression, which can arise due to another medical or psychological issue. Participants experienced few adverse effects, and most were mild and transient. Interestingly, those who had used psychedelics before experienced greater symptom relief, possibly due to “expectancy bias” – a phenomenon where a person’s previous experience makes them expect positive results.

These findings suggest that psilocybin exerts potent antidepressant effects. Although the treatment response was high, the review’s authors graded the quality of the evidence as “low” due to heterogeneity among the studies, including dose and concomitant psychotherapy.

Psilocybin is a psychedelic compound present in mushrooms. Learn more about the effects of psilocybin and other psychedelic drugs in this episode featuring Dr. Roland Griffiths.