This study followed 52 people who attended psilocybin retreats in the Netherlands and measured their anxiety levels before, one day after, and one week after the experience. Participants showed significant reductions in both immediate anxiety (state anxiety) and long-term anxiety tendencies (trait anxiety) that lasted up to a week. The anxiety improvements were most strongly linked to feeling a sense of ego dissolution during the experience and to lasting changes in personality traits, particularly becoming less neurotic.