Mystical-type experiences occasioned by psilocybin mediate the attribution of personal meaning and spiritual significance 14 months later

Abstract

Psilocybin has been used for centuries for religious purposes; however, little is known scientifically about its long-term effects. We previously reported the effects of a double-blind study evaluating the psychological effects of a high psilocybin dose. This report presents the 14-month follow-up and examines the relationship of the follow-up results to data obtained at screening and on drug session days. Participants were 36 hallucinogen-naïve adults reporting regular participation in religious/ spiritual activities. Oral psilocybin (30 mg/70 kg) was administered on one of two or three sessions, with methylphenidate (40 mg/70 kg) administered on the other session(s). During sessions, volunteers were encouraged to close their eyes and direct their attention inward. At the 14-month follow-up, 58% and 67%, respectively, of volunteers rated the psilocybin-occasioned experience as being among the five most personally meaningful and among the five most spiritually significant experiences of their lives; 64% indicated that the experience increased well-being or life satisfaction; 58% met criteria for having had a 'complete' mystical experience. Correlation and regression analyses indicated a central role of the mystical experience assessed on the session day in the high ratings of personal meaning and spiritual significance at follow-up. Of the measures of personality, affect, quality of life and spirituality assessed across the study, only a scale measuring mystical experience showed a difference from screening. When administered under supportive conditions, psilocybin occasioned experiences similar to spontaneously occurring mystical experiences that, at 14-month follow-up, were considered by volunteers to be among the most personally meaningful and spiritually significant of their lives.

Figure 1

Total score on lifetime version of the Mysticism Scale at screening, 2 months following psilocybin, and at the 14-month follow-up. Bars are mean scores with brackets showing 1 S.E.M. (N=36). Asterisks show significant differences from the screening assessment. For comparison, lower dashed line shows mean score for college students (Hood et al., 2001; Hood, 2007); upper dashed line show maximum possible score.

Figure 2

Percentage of volunteers endorsing specific answers on the Persisting Effects Questionnaire completed 2 months following the methylphenidate (Methp) and psilocybin (Psil) sessions (n=29), and again retrospectively for psilocybin at the 14-month follow-up (N=36). For ratings of personally meaningful and spiritually significant (top two panels), the data are the percentage rating “among the top 5” or “the single most.” For ratings of increased well-being or life satisfaction, the data are the percentage rating “increased moderately” or “increased very much.” For ratings of positive behavioral change, the data are the percentage rating “moderate”, “strong”, or “extreme.” Asterisks show significant differences (p<.05, z-test of proportions, n=29 at each assessment) from the methylphenidate 2-month assessment; there were no significant differences between the psilocybin 2-month condition and the psilocybin 14-month follow-up assessment. For the methylphenidate results, the data presented are from the first methylphenidate session for the 5 subjects who received methylphenidate on two sessions and who completed this questionnaire.

Figure 3

Ratings of the spiritual significance of the psilocybin session experience at the 14-month follow-up as a function of subject ratings complete 7 hours after psilocybin administration on the Mysticism Scale (upper panel) and the Intensity subscale of the Hallucinogen Rating Scale (HRS). Data points represent individual subject data (N=36); slope and correlation coefficients are shown.