The serotonin system and spiritual experiences.

OBJECTIVE The serotonin system has long been of interest in biological models of human personality. The purpose of this positron emission tomography (PET) study was to search for relationships between serotonin 5-HT(1A) receptor density and personality traits. METHOD Fifteen normal male subjects, ages 20-45 years, were examined with PET and the radioligand [(11)C]WAY100635. Personality traits were assessed with the Swedish version of the Temperament and Character Inventory self-report questionnaire. Binding potential, an index for the density of available 5-HT(1A) receptors, was calculated for the dorsal raphe nuclei, the hippocampal formation, and the neocortex. For each region, correlation coefficients between 5-HT(1A) receptor binding potential and Temperament and Character Inventory personality dimensions were calculated and analyzed in two-tailed tests for significance. RESULTS The authors found that the binding potential correlated inversely with scores for self-transcendence, a personality trait covering religious behavior and attitudes. No correlations were found for any of the other six Temperament and Character Inventory dimensions. The self-transcendence dimension consists of three distinct subscales, and further analysis showed that the subscale for spiritual acceptance correlated significantly with binding potential but not with the other two subscales. CONCLUSIONS This finding in normal male subjects indicated that the serotonin system may serve as a biological basis for spiritual experiences. The authors speculated that the several-fold variability in 5-HT(1A) receptor density may explain why people vary greatly in spiritual zeal.