Nanocarriers in psychiatry: a comprehensive review of emerging frontiers in the management of psychiatric disorders.

Psychiatric disorders are characterized by clinically significant disturbances in cognition, emotional regulation, and behavior and represent a substantial global health burden. Pharmacological management relies primarily on antidepressants, anxiolytics, antipsychotics, mood stabilizers, hypnotics, and stimulants. However, conventional therapy may be limited by unfavorable physicochemical properties, variable pharmacokinetics, suboptimal brain exposure, frequent dosing, and systemic adverse effects, which may compromise therapeutic outcomes and long-term treatment adherence. Nanocarrier-based drug delivery systems have emerged as a promising approach to address some of these limitations. By optimizing particle size, composition, morphology, and surface characteristics, nanocarriers may improve drug solubility and stability, modify pharmacokinetic and release profiles, protect therapeutic agents from degradation, and facilitate brain delivery through the blood-brain barrier-associated transport mechanisms or nose-to-brain pathways. Controlled or sustained release may additionally reduce dosing frequency and improve patients' compliance. This review critically examines organic, inorganic, and hybrid nanocarrier systems investigated for psychotropic drug delivery, with particular emphasis on brain delivery mechanisms, safety considerations, clinical translation, regulatory challenges, and emerging strategies for psychiatric nanomedicine.