Psychopharmacology at an Inflection Point: From Syndromes to Stratified Mechanisms, Circuit-Based Treatments, and...

Psychopharmacology, once propelled by a series of serendipitous mid-20th-century discoveries, has matured into a field defined by mechanistic diversity, translational neuroscience, and an expanding array of circuit-based interventions. Despite more than 100 approved psychiatric drugs, remission rates for major depressive disorder and other serious mental disorders remain modest, underscoring the biological heterogeneity embedded within syndromic diagnoses. Roughly 60% of patients with major depressive disorder respond to monoaminergic treatments, while others respond preferentially to glutamatergic agents such as ketamine or esketamine, and a smaller subset remains minimally responsive to both. These differential response patterns challenge the notion of a singular depressive disorder and highlight the need for biologically informed patient stratification. Contemporary psychopharmacology extends well beyond classic neurotransmitter modulation, encompassing synaptic plasticity, circuit regulation, inflammatory pathways, neurosteroids, muscarinic systems, drug-assisted psychotherapies, and computational neuroscience. Parallel advances in neuromodulation, including repetitive transcranial magnetic stimulation, transcranial direct current stimulation, vagus nerve stimulation, focused ultrasound, and adaptive deep brain stimulation, reflect a shift from region-based to network-based conceptualizations of psychiatric illness. Simultaneously, advances in pharmacogenomics, neuroimaging, artificial intelligence, and biomarker identification are beginning to make precision psychiatry a practical, though still emerging, reality. With these broadly described advances in mind, this column reflects on the historical trajectory of psychopharmacology, explores the convergence of pharmacology and neuromodulation, and considers the future of psychiatry through the lens of mechanism-based and personalized care. In doing so, it aims to carry forward the disciplined, mechanistically grounded scholarship that has long characterized this column.