Definition
Schizophrenia is a serious and persistent psychiatric disorder defined by disturbances in thought, perception, emotion, and behavior. Its diagnostic core includes positive symptoms — features that should be absent but are present, such as hallucinations and delusions — and negative symptoms — features that should be present but are diminished, such as emotional expression, motivation, and social engagement. Cognitive disorganization, including disrupted thinking, speech, and attention, accompanies these in many cases. The term was coined by Eugen Bleuler in 1908 to describe a "splitting" of mental functions, not a split personality as is widely misunderstood.
Onset typically occurs in late adolescence or early adulthood and the condition usually follows a chronic course with periods of exacerbation and partial remission. Worldwide prevalence is around one percent of the adult population, and the disorder ranks among the leading causes of long-term disability, partly through its direct symptoms and partly through the social consequences that accumulate when severe illness begins early in adult life.
Why it matters
How it works
The biological account places dopaminergic dysregulation at the center of schizophrenia. Excess dopamine signaling in mesolimbic pathways is associated with positive symptoms, while reduced signaling in prefrontal mesocortical pathways is linked to negative and cognitive symptoms. Antipsychotic medications act primarily by blocking dopamine D2 receptors, which reliably reduces positive symptoms but leaves negative and cognitive features less responsive. Beyond dopamine, abnormalities in glutamate signaling, neurodevelopmental wiring, and grey-matter volume have all been documented, suggesting schizophrenia is best understood as a disorder of brain development whose symptoms emerge once the maturing brain reaches a particular configuration.
The clinical picture has been reshaped by an emphasis on early intervention. Specialized early-psychosis services aim to identify and treat first episodes quickly, on the evidence that a shorter duration of untreated psychosis is associated with better long-term outcomes. Treatment combines antipsychotic medication with structured psychosocial care: cognitive-behavioral therapy for psychosis works directly on the appraisal of hallucinations and delusions, family intervention reduces relapse by reducing high-expressed-emotion home environments, and supported employment and education help preserve the social trajectory that the illness threatens. Stigma — fueled by the persistent confusion of schizophrenia with violence or split personality — remains a significant barrier to recovery and is now itself a target of public-education work.