Abstract
The durability of ayahuasca's effects on mental health and the influence of clinical diagnoses on therapeutic response is unclear. Adults with no prior exposure to ayahuasca (n = 66) participating in neo-shamanic ayahuasca ceremonies completed questionnaires at baseline, 7 days, and 1, 6, and 12 months. Mixed models were used to characterize temporal trajectories in mental health, alcohol and cannabis use, affect, personality, spirituality, and relationships and examine the longevity of effects in individuals with and without a depressive or anxiety disorder. After multiple comparison correction, ayahuasca use was associated with decreases in depression, anxiety, stress, negative affect, negative emotionality, acceptance of external influence, and self-alienation at all time points. Improvements in mental health, self-efficacy, and spirituality were observed up to 12 months post-ceremony. Individuals with depression and anxiety diagnoses maintained significant symptom reductions, whereas those without a diagnosis experienced short-term benefits. Decreases in alcohol and cannabis use were only observed at month 1. Naturalistic ayahuasca use was associated with persisting improvements in mental health and wellbeing, with the largest magnitude of symptom reduction observed in those diagnosed with a depressive or anxiety disorder. Differing trajectories of change were identified across psychological constructs, suggestive of both enhancement and attenuation of gains over time.