Classic psychedelics in obsessive–compulsive disorder: a circuit-based framework
Nature Mental Health April 1, 2026 Saif S. Ali, Robin L. Carhart-Harris, Karl G. Sieg
LSD and psilocybin may help treat obsessive-compulsive disorder (OCD) by disrupting maladaptive brain circuits and enhancing neuroplasticity. OCD involves dysfunction in the cortico-striatal-thalamo-cortical circuit, default mode network, and salience network. Psychedelics acutely dysregulate the default mode network and increase connectivity between normally segregated networks, potentially breaking cycles of rumination and self-referential thought. They also modulate the cortico-striatal-thalamo-cortical circuit and rapidly promote dendritic spine formation via 5-HT2A receptors in rodents. These dual mechanisms could reset pathological patterns and support long-term restructuring of maladaptive circuits, but clinical trials with neuroimaging endpoints are needed to validate this framework.