Etiology and Pathophysiology of Schizophrenia

1. Overview & Epidemiology

• Definition: Schizophrenia is a chronic psychotic disorder of complex, multifactorial etiology — genetic vulnerability interacting with environmental and neurodevelopmental insults. No single cause is proven (the explicit point of PSY-4.50).
• Lifetime prevalence: ~1% worldwide (1 in 100); broadly uniform across cultures.
• Sex: Affects males and females equally, but onset is earlier in men (peak 20–28 yrs) than women (peak 26–32 yrs). The later/bimodal female onset is attributed in part to a protective estrogen effect (a dopaminergic modulator).
• Incidence: ~0.5–5.0 per 10,000/yr, with **geographic variation — higher i