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Review
. 2018:36:393-430.
doi: 10.1007/7854_2017_474.

Classic Hallucinogens and Mystical Experiences: Phenomenology and Neural Correlates

Frederick S Barrett  1 , Roland R Griffiths  2   3
Affiliations
Review

Classic Hallucinogens and Mystical Experiences: Phenomenology and Neural Correlates

Frederick S Barrett et al. Curr Top Behav Neurosci. 2018.

Abstract

This chapter begins with a brief review of descriptions and definitions of mystical-type experiences and the historical connection between classic hallucinogens and mystical experiences. The chapter then explores the empirical literature on experiences with classic hallucinogens in which claims about mystical or religious experiences have been made. A psychometrically validated questionnaire is described for the reliable measurement of mystical-type experiences occasioned by classic hallucinogens. Controlled laboratory studies show that under double-blind conditions that provide significant controls for expectancy bias, psilocybin can occasion complete mystical experiences in the majority of people studied. These effects are dose-dependent, specific to psilocybin compared to placebo or a psychoactive control substance, and have enduring impact on the moods, attitudes, and behaviors of participants as assessed by self-report of participants and ratings by community observers. Other studies suggest that enduring personal meaning in healthy volunteers and therapeutic outcomes in patients, including reduction and cessation of substance abuse behaviors and reduction of anxiety and depression in patients with a life-threatening cancer diagnosis, are related to the occurrence of mystical experiences during drug sessions. The final sections of the chapter draw parallels in human neuroscience research between the neural bases of experiences with classic hallucinogens and the neural bases of meditative practices for which claims of mystical-type experience are sometimes made. From these parallels, a functional neural model of mystical experience is proposed, based on changes in the default mode network of the brain that have been observed after the administration of classic hallucinogens and during meditation practices for which mystical-type claims have been made.

Keywords: Angular gyrus; Default mode network; Hallucinogens; Inferior parietal lobule; Medial prefrontal cortex; Meditation; Mystical experiences; Neural model; Posterior cingulate; Psilocybin.

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Figures

Figure 1.
Figure 1.
Mystical experience on session days predicts ratings of spiritual significance at 14 months. Total score on the 30-item Mystical Experience Questionnaire (MEQ30) is expressed as the percent of the maximum possible score. Data points represent individual participants (n=36). B = slope of the regression of spiritual significance on mystical experience questionnaire total score. SE = standard error of the slope (B). Adjusted R2 indicates the amount of variance in spiritual significance ratings that is explained by the mystical experience questionnaire total score. MEQ30 data have been rescored from MEQ43 responses reported in Griffiths et al., 2008.
Figure 2.
Figure 2.
Measures of mystical experience on session days as a function of psilocybin dose. “Dose Effects Study” data (5 pairs of bars at the left) show the dose-related effect of psilocybin on two measures of mystical experience (Griffiths et al 2011). “3 studies” observations (bars at the right) show post-session ratings from the first high-dose (30 mg/70 kg) session administered in each of 3 studies (Griffiths et. al. 2006, , unpublished study in beginning meditators). Dark bars show the percentage of volunteers who met criteria for having a complete mystical experience. Lighter bars show the mean Mystical Experience Questionnaire total score expressed as a percentage of maximum possible score; brackets show ± 1 S.E.M. Categorizations of complete mystical experiences and calculations of total scores were based on the 30-item Mystical Experience Questionnaire (MEQ30).
Figure 3.
Figure 3.
Follow-up ratings of spiritual experience and positive behavior change as a function of psilocybin dose. “Dose Effects Study” data (5 pairs of bars at the left) show the dose-related effect of psilocybin on retrospective ratings assessed 1 month after sessions (Griffiths et al., 2011). “3 studies” observations (bars at the right) show retrospective ratings assessed 3 to 8 weeks after the first high-dose (30 mg/70 kg) session administered in each of 3 studies (Griffiths et. al. 2006, , unpublished study in beginning meditators). Dark bars show the percentage of volunteers who rated their session as within the top five or single most spiritual experience of their life. Lighter bars show the percentage of volunteers who rated a moderate or greater degree of positive behavior change at follow-up.
Figure 4.
Figure 4.
Revised 30-item Mystical Experience Questionnaire (MEQ30). The MEQ30 is a psychometrically-validated retrospective measure of mystical experience. The 4 factors of the psychometrically validated questionnaire are derived from a total of 30 items that probe 7 dimensions (designated by underlines) of mystical experience that were identified by Stace (1960). The Mystical factor is composed of 15 items probing four dimensions of the Stace model (internal unity, external unity, noetic quality, and sacredness). Positive Mood (6 items), Transcendence of Time and Space (6 items) and Ineffability (3 items) factors correspond to three separate dimensions of the Stace model.
Figure 5.
Figure 5.
Mystical experience scores on session days predicts change in smoking craving score at 6 months. X-Axis: total score on the 30-item version of the Mystical Experience Questionnaire (MEQ30) expressed as the percent of the maximum possible score. Y-Axis: difference in score on the Questionnaire on Smoking Urges between study intake and 6-month follow-up. Data points represent individual participants (n=15). B = slope of the regression of cigarette smoking craving change score on mystical experience questionnaire total score, SE = standard error of the slope (B). Adjusted R2 indicates the amount of variance in spiritual significance ratings that is explained by mystical experience questionnaire total score. MEQ30 data have been rescored from MEQ43 responses reported in Garcia-Romeu et al. 2015.
Figure 6.
Figure 6.
Mystical experience on session days predicts change in anxiety at 5 weeks post-psilocybin. X-Axis: total score on the 30-item version of the Mystical Experience Questionnaire (MEQ30) expressed as the percent of the maximum possible score. Y-Axis: difference in score on the Hamilton Anxiety Rating Scale between baseline and 5-week follow-up. Data points represent individual participants (n=51). r = Pearson product moment correlation between HAM-A and MEQ30 scores. Data are from Griffiths et al., 2016.
Figure 7.
Figure 7.
Similar deactivations in the medial default mode network during meditation and experience with psilocybin. The upper portion of the figure illustrates approximate locations of the medial prefrontal cortex (labeled in green) and posterior cingulate cortex (labeled in red). The center portion of the figure (adapted from Carhart-Harris et al 2014, Figure 4, with permission), shows regions in the medial default mode network, including the medial prefrontal cortex and posterior cingulate, where both deactivation in blood-oxygenation-level-dependent (BOLD) data and decrease in cerebral blood flow (CBF) were observed after intravenous injection of psilocybin. The lower portion of the figure (adapted from Brewer et al 2011, Figure 1, with permission) shows regions in the medial default mode network, including the medial prefrontal cortex and posterior cingulate, where decreases in BOLD data were observed during meditation. The decreased activity within the medial prefrontal cortex and posterior cingulate which is observed after psilocybin and during meditation is consistent with decreased self-referential processing that accompanies introvertive mystical experience.
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