The persistent gap between psychiatric diagnosis and effective biological treatment is one of medicine's most stubborn failures. Roughly half of patients with depression, schizophrenia, or anxiety disorders achieve only partial remission on existing medications, and side-effect burdens drive high non-adherence. A comprehensive new review argues the field has been fishing in too small a pond — and identifies the largely untapped neurochemical systems that may hold the next generation of targets.
Published in the Journal of Neurochemistry and originating from the International Society for Neurochemistry's 2024 Flagship School, this review maps the pathophysiological roles of neuromodulatory systems that have historically received secondary attention. Beyond the classical dopamine and serotonin axes, the authors catalog the contributions of histamine, acetylcholine, norepinephrine, endocannabinoids, neuropeptides, trace amines, and cytokines to circuit-level dysfunction across depression, schizophrenia, autism spectrum disorder, and alcohol use disorder. Each system is framed not as a curiosity but as a mechanistically plausible intervention point — one where dysfunction has been documented in human imaging, post-mortem, and preclinical data alike.
The review's broader significance lies in its timing and framing rather than any single novel discovery. The past decade has seen clinical proof-of-concept for several of these pathways: ketamine's glutamatergic mechanism reshaped depression treatment; CB1 receptor modulation has entered anxiety and PTSD trials; trace amine-associated receptor 1 (TAAR1) agonists have reached Phase III trials for schizophrenia. What this synthesis offers is a conceptual scaffold that connects these scattered advances into a coherent research agenda. The chief limitation is inherent to the review format: mechanistic understanding does not automatically translate to druggable targets or tolerable therapies. Identifying a neuromodulatory system's role in pathophysiology has repeatedly proven easier than converting that knowledge into clinical benefit. Still, for a field that has relied on serendipitous pharmacology for seven decades, a mechanism-first framework represents a meaningful philosophical shift — and potentially a more efficient path to treatments that modify disease course rather than mask symptoms.
