Learning as the unifying mechanism of psychedelic action

Abstract

Psychedelics are gaining attention as putative treatments for a range of psychiatric conditions, and evidence suggests that they produce sustained behavioural and clinical change. Enhanced learning is an emerging candidate mechanism mediating these sustained effects. This narrative review synthesises evidence across behavioural, neural and computational levels to examine the current evidence base for how psychedelics may alter learning mechanisms. We propose that viewing psychedelic mechanisms through the lens of learning unifies context-dependent outcomes, increased environmental sensitivity and neuroplastic change. We discuss how persistent changes in top-down and bottom-up information processing at a systems-level may account for both the therapeutic and adverse effects of psychedelics, and highlight a mechanistic convergence between such systems-level changes and the recently identified psychedelic-mediated reopening of critical learning periods. This systems-level framework may explain why psychedelic outcomes vary widely and hinge critically on the context: it is the learning environment, including psychological support and therapeutic insights, which shapes the lasting effect. If the post-psychedelic period is characterised by a vulnerable neuroplastic state in combination with increased environmental sensitivity, usually observed uniquely during childhood, this would offer a window of opportunity for revision of entrenched beliefs. Understanding these mechanisms has important translational relevance for the design and implementation of psychedelic-assisted psychotherapy.