Single Dose of Psilocybin Linked to Lasting Personality Shifts
A landmark study from Johns Hopkins University found that a single dose of psilocybin — the psychoactive compound found in certain species of mushrooms — produced measurable personality changes that lasted well over a year. The research, published in the Journal of Psychopharmacology, offers some of the most compelling evidence to date that a brief psychedelic experience can reshape core personality traits in a durable way.
The study involved 52 adult volunteers who underwent controlled sessions in which they received psilocybin under carefully supervised conditions. Participants had been counseled extensively beforehand, and the drug was administered in supportive environments designed to minimize negative reactions — a protocol considered standard practice in human hallucinogen research.
What the Researchers Measured and How
Led by Katherine A. MacLean, PhD, and her colleagues at Johns Hopkins, the team drew from two separate blinded crossover studies that had already been individually published. In one arm, participants received a relatively high dose of psilocybin (30 mg per 70 kg of body weight) versus methylphenidate as an active control during eight-hour sessions. In the other arm, participants underwent five sessions receiving either placebo or psilocybin at doses ranging from 5 to 30 mg per 70 kg.
Personality was assessed using the NEO Personality Inventory, a well-established instrument that evaluates five dimensions: openness, extroversion, neuroticism, agreeableness, and conscientiousness. Evaluations occurred at baseline, one to two months after each session, and approximately 14 months after the final session. The acute psychosensory effects during each session were also documented through questionnaires designed to capture the depth of any reported mystical experiences.
Openness Increased — and Stayed Elevated for Over a Year
Among the five personality dimensions tracked, only openness showed significant change. Openness encompasses traits such as aesthetic appreciation, imaginative engagement, intellectual curiosity, and heightened awareness of one’s own emotions and those of others. At baseline, participants averaged about 64 on the openness scale. Following the high-dose psilocybin sessions, scores rose by an average of 2.8 points.
The critical variable turned out to be the quality of the subjective experience during the session itself. Participants who met the criteria for a “complete mystical experience” — 30 out of 52 — saw their openness scores jump by an average of 5.7 points. Those who did not reach this threshold showed no meaningful change. This correlation between mystical experience ratings and increased openness was statistically significant (r=0.42, P=0.002).
At the 14-month follow-up, participants who had undergone complete mystical experiences still scored significantly higher in openness than they had at baseline, with scores remaining elevated by 4.2 points (P=0.05). Participants without mystical experiences showed no long-term personality changes whatsoever.
No Adverse Effects Were Reported
Importantly, the research team found no adverse effects from the psilocybin exposure. The other four personality dimensions — extroversion, neuroticism, agreeableness, and conscientiousness — remained statistically unchanged throughout the study period. The researchers also checked whether participants who were already high in openness before the study were more likely to have mystical experiences, and found no such correlation (r=0.12, P=0.41).
How Psilocybin Works in the Brain
Psilocybin is a naturally occurring compound found in various mushroom species. It acts primarily on the serotonin 5-HT2A receptor in the brain. The substance gained widespread cultural attention in the 1960s for producing vivid hallucinatory and introspective experiences. Users have historically reported increased creativity, deeper appreciation of music and visual art, and greater tolerance toward other people.
The findings from this Hopkins study aligned with those earlier anecdotal reports and with previous research suggesting that psilocybin can alter how people relate to the world long after its acute pharmacological effects have dissipated.
Broader Implications for Mental Health and Addiction Treatment
The researchers noted that their findings open new avenues for investigating the biological and psychological mechanisms behind psilocybin’s lasting effects. They also suggested that mystical experiences triggered through non-pharmacological means — such as meditation or deep spiritual practice — could potentially produce similar long-term personality shifts, a hypothesis they argued deserves further study.
This line of inquiry is particularly relevant given that mystical experiences, whether drug-induced or not, have been linked in other research to helping individuals overcome addictions and cope with cancer and other life-threatening illnesses.
Study Limitations Worth Noting
The researchers acknowledged several important caveats. Participants were self-selected rather than randomly drawn from the general population, meaning they were already inclined toward introspection and psychedelic exploration. Nearly all engaged regularly in spiritual activities including religious services, prayer, and meditation, potentially making them more sensitive to psilocybin’s effects.
Additionally, baseline neuroticism scores among participants were nearly one standard deviation below the general population average, suggesting this was already a psychologically stable group. As a result, the team conceded that the drug’s effects could not be fully separated from the self-selection bias inherent in the study design.
A Growing Body of Evidence for Psychedelic-Assisted Research
The study was funded by the National Institute on Drug Abuse, the Council on Spiritual Practices, the Heffter Research Institute, and the Betsy Gordon Foundation. All authors declared no relevant financial interests. The primary source publication was MacLean K, et al., “Mystical experiences occasioned by the hallucinogen psilocybin lead to increases in the personality domain of openness,” published in the Journal of Psychopharmacology in 2011.
This research represents one piece in a growing mosaic of evidence suggesting that psychedelic compounds, when administered responsibly under clinical supervision, may hold genuine therapeutic potential — not just for treating specific conditions, but for fundamentally expanding the way individuals perceive and engage with the world around them.
