Microglia in Psychiatric Disorders: Stage-Dependent Roles and Therapeutic Implications

Psychiatric disorders, including schizophrenia, mood disorders, and neurodevelopmental disorders, arise from complex interactions between genetic vulnerability and environmental exposures and have traditionally been viewed as diseases resulting from neuronal abnormalities. In recent years, however, growing evidence has highlighted the critical role of non-neuronal cells—particularly microglia—in the pathogenesis of these conditions. Microglia are the resident immune cells of the central nervous system and play essential roles in shaping neural circuits through synaptic pruning and formation. Importantly, microglial functions are not static; they are dynamically regulated in a stage-dependent manner across prenatal, postnatal, and adolescent periods, and disruption at each stage confers distinct risks for psychiatric pathology. In this review, we summarize recent evidence implicating microglia in the pathophysiology of psychiatric disorders, with particular emphasis on how the developmental stage at which microglial dysfunction occurs determines the timing and nature of disease onset. Furthermore, we discuss the therapeutic potential of pharmacological interventions targeting microglial functions in a stage-dependent manner.