Swedish adults who have used psychedelics at least once report less depression than non-users who are the same sex and age, but also report more drug use. The difference in depression is partly explained by lower neuroticism among users. Psychedelic users also score much higher on openness to experience, a personality trait. The findings come from a national online survey comparing 400 psychedelic users with 400 matched non-users.
A systematic review of nine studies on psychedelic-assisted therapy found that masking success was rarely reported and almost 78% of the studies had at best poor masking. Among active placebo studies, 60% showed large effect sizes, and among inactive placebo studies, 75% showed large effect sizes. Masking influences, including benign unmasking, cannot be excluded. Therefore, the efficacy of psilocybin, ayahuasca, or LSD is only one possible interpretation of large positive changes in symptoms for conditions like alcohol use disorder, anxiety, depression, and treatment-resistant depression. The authors recommend improving masking procedures and considering alternative trial designs.