Schizophrenia is a complex mental disorder that typically emerges in late adolescence or early adulthood, with onset usually between ages 16–30. It rarely begins before puberty or after age 45. The exact cause is unknown, but it arises from a combination of genetic, biological, environmental, and neurodevelopmental factors rather than a single trigger.

Genetic Factors: Schizophrenia has a strong hereditary component. Having a first-degree relative (parent or sibling) with the disorder increases risk 10-fold, from ~1% in the general population to ~10%. Twin studies show concordance rates of 40–50% in identical twins versus 10–15% in fraternal twins, pointing to genetics. Over 100 gene variants, like those affecting dopamine regulation (e.g., DRD2) or glutamate (e.g., GRIN2A), contribute subtly.

Brain Chemistry and Structure: Imbalances in neurotransmitters, especially excess dopamine in mesolimbic pathways, drive positive symptoms (hallucinations, delusions). Reduced glutamate activity impairs cognition. Brain imaging reveals enlarged ventricles, reduced gray matter in prefrontal and temporal lobes, and disrupted connectivity often present before symptoms.

Environmental Triggers: Prenatal insults (maternal infections, malnutrition, stress) or birth complications raise risk via neurodevelopmental disruption. Childhood trauma, urban upbringing, or cannabis use (especially high-THC strains in adolescence) can precipitate onset in genetically vulnerable individuals. Migration and social adversity also correlate with higher rates.

Prodromal Phase: Symptoms don't appear suddenly. A prodrome lasts months to years, with subtle changes like social withdrawal, odd beliefs, flattened emotions, or attenuated psychosis (mild hallucinations). This transitions to acute psychosis if untreated.

Early intervention during prodrome improves outcomes. Risk calculators (e.g., combining genetics, biomarkers) aid prediction, but diagnosis requires persistent symptoms per DSM-5. Consult a psychiatrist for concerns.