The profound mismatch between the growing autism diagnosis rate and the near-total absence of treatments targeting its neurobiological roots makes this review timely. The two approved pharmacological options — risperidone and aripiprazole — address behavioral symptoms through dopamine blockade without touching the serotonergic dysregulation, impaired synaptic plasticity, or chronic neuroimmune activation now recognized as core features of autism spectrum disorder (ASD). A mechanistically grounded alternative has been largely absent — until the psychedelic renaissance reopened the question.
This review, published in Progress in Neuro-Psychopharmacology & Biological Psychiatry, synthesizes molecular through systems-level evidence for serotonergic psychedelics — principally psilocybin and LSD — as candidate ASD therapeutics. Both compounds act as high-affinity 5-HT2A receptor agonists, and the review argues they may address ASD through at least three converging mechanisms: upregulating synaptic plasticity via BDNF and mTOR pathways, recalibrating cortical excitatory-inhibitory balance and oscillatory dynamics, and shifting microglial phenotypes away from pro-inflammatory states. Critically, the authors invoke the REBUS (Relaxed Beliefs Under Psychedelics) framework and the anarchic brain hypothesis to explain how psychedelics may transiently loosen the rigid, hyper-segregated cortical connectivity characteristic of ASD — effectively reopening developmental critical periods for social learning.
Positioning this work in the broader landscape, the serotonin-autism connection is not new — early observations of hyperserotonemia in autistic individuals date to the 1960s — but the specific mechanism linking 5-HT2A agonism to neuroplasticity restoration represents a genuinely evolved hypothesis. The critical-period reopening concept draws strength from well-replicated animal work showing that psychedelics can reinstate juvenile-like synaptic malleability in adult cortex. However, the leap from that preclinical substrate to clinical benefit in ASD remains largely unvalidated in humans. Trial populations have been small, diagnostic heterogeneity in ASD is enormous, and the subjective psychedelic experience itself raises profound challenges for consent and distress management in non-speaking or sensory-sensitive individuals. This review is best read as a rigorous mechanistic scaffold for clinical hypotheses rather than a therapeutic endorsement — an important distinction as early trials begin to emerge.