Mechanisms of integration in psychedelic-assisted therapy.

Introduction: In recent clinical trials, psychedelic-assisted psychotherapy (PAP) led to symptomatic improvement among people with several psychiatric conditions. PAP has three distinct phases: preparation, support during psychedelic administration, and integration. The purpose of this scoping review was to identify randomized controlled trials that used PAP and synthesize the research base related to neuronal networks and neural function as measured with neuroimaging during the integration period and to link these findings to psychological changes after PAP. Methods: PubMed and ProQuest databases were searched using key words. Inclusion and exclusion criteria were used to determine whether an article would be reviewed. The authors specifically focused on articles that used neuroimaging or reported a psychological outcome one day or more after psychedelic administration. Results: Most articles used functional magnetic resonance imaging (fMRI) and, in particular, resting-state fMRI to assess functional connectivity. Results generally reported changes in higher-order networks, although the direction of change in strength of connectivity was variable. Themes related to psychological findings were linked to increases in psychological and cognitive flexibility, increased openness, and decreased neuroticism after psychedelic treatment. Discussion: In general, more consistent methodology across the field should be applied to make progress in understanding network-based changes underlying clinical improvements after PAP. Limited evidence suggests that changes in the executive control network, and in its integration with other networks, may result in greater cognitive flexibility during the integration period.