Can one psilocybin session change personality? The 2011 study on openness
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The question
Personality tends to be fairly stable in adulthood, especially after about age 30. Psychologists often describe it in five broad areas: neuroticism, extraversion, openness, agreeableness and conscientiousness. "Openness" covers curiosity, imagination, appreciation of art and beauty, awareness of one's feelings, and openness to new ideas and values.
Researchers at Johns Hopkins asked a simple question. Could a single, carefully guided psilocybin session lead to a lasting change in personality? And if so, did it depend on whether the person had a mystical-type experience (a strong sense of unity, meaning and deep peace) during the session?
Who took part and what happened
This study did not recruit new people. Instead, it pooled data from two earlier Johns Hopkins psilocybin studies, both double-blind (neither volunteers nor session staff knew which dose was given on a given day). Together they included 52 healthy adults (30 women, 22 men, average age 46). None had used hallucinogens before, and most were active in some spiritual practice.
Each person had between two and five day-long sessions, at least three weeks apart. The analysis focused on one session: a high dose of psilocybin (30 mg per 70 kg of body weight). Sessions took place in a comfortable living-room-style space, with two trained monitors present throughout.
Personality was measured with a standard, widely used questionnaire (the NEO Personality Inventory). People filled it out at the start, again one to two months after the high-dose session, and again at a long-term follow-up, which took place on average about 16 months later. The researchers also used a questionnaire to see who had a "complete" mystical experience during the session (scoring at least 60% on each of six parts of the scale).
What they found
- Openness went up after the high-dose session. Across all 52 people, openness rose by an average of 2.8 points on the standard scale.
- The change was linked to mystical experience. Thirty of the 52 volunteers (a bit more than half) had a complete mystical experience. In this group, openness rose by 5.7 points. In the other 22 people, it rose by only 1.2 points, which was not a meaningful change.
- It lasted. At the long-term follow-up (about 16 months on average), the mystical-experience group was still 4.2 points above where they started. The other group was back near their starting point.
- Several sides of openness changed. The increase showed up in imagination, appreciation of beauty and art, awareness of feelings, openness to ideas, and openness in values.
- Other traits did not change. There were no significant changes in neuroticism, extraversion, agreeableness or conscientiousness.
To put this in context: openness usually drifts down by about 1 point per decade as adults age. The increase of more than 4 points in the mystical-experience group was larger than that. The authors also noted that it was larger than changes reported in earlier studies of antidepressant treatment or substance-use counseling.
What this study does not tell us
- A small, unusual group. Fifty-two people is a small sample. They were motivated, unpaid, healthy volunteers, and most were spiritually active. Results may differ in other people.
- Pooled studies. The data came from two separate studies that were not designed to answer this exact question. In one of them, people also had other doses, so the effect of the high-dose session cannot be fully separated.
- No comparison for the personality change. The analysis compared people with and without a mystical experience. It did not compare them with a group that never received psilocybin.
- Self-reported personality. Personality was measured by questionnaires people filled out themselves. The mystical-experience questionnaire used here had not been formally validated at the time.
- Careful conditions. Volunteers were screened, prepared and supported by trained staff. The same results may not appear in other settings.
Why it matters
This was one of the first studies to show a measurable, lasting change in an adult personality trait after a single, controlled event. The change was modest and limited to one trait. It appeared mainly in people who had a mystical-type experience during the session.
The authors called for larger studies with more varied participants. Openness is linked in other research to creativity and to how people approach new experiences, so this remains an active area of study.
This is a summary of published research for general information. It is not medical advice. The study took place in a clinical research setting with medical screening and professional support.
Source: MacLean, K. A., Johnson, M. W., & Griffiths, R. R. (2011). Mystical experiences occasioned by the hallucinogen psilocybin lead to increases in the personality domain of openness. Journal of Psychopharmacology, 25(11), 1453–1461. doi:10.1177/0269881111420188 · PubMed · Full text
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