The corpus callosum, a brain structure connecting the two hemispheres, was thicker in the isthmus region among 22 ayahuasca users compared to 22 matched controls. A positive correlation was observed between callosal thickness in the rostral body and the number of past ayahuasca sessions, though neither finding survived correction for multiple comparisons. No brain region was thicker in controls than in ayahuasca users, and no region was negatively linked to ayahuasca use. This provides preliminary evidence of an association between ayahuasca use and callosal structure, but replication with larger samples and longitudinal designs is needed.
Ayahuasca, a psychoactive brew used as an entheogen for centuries, is being investigated as a treatment for clinical disorders. This study analyzed open-ended descriptions from nine people with treatment-resistant depression and twenty healthy controls after their first ayahuasca experience. Using quantitative textual analysis, five clusters emerged: altered consciousness, cognitive changes, somatic alterations, auditory experiences, and visual content. People with depression reported more aversive bodily reactions. The findings align with known psychedelic experience patterns and may guide therapeutic use of ayahuasca.