Schizophrenia

Description

• Major psychiatric disorder characterized by prodrome, active, and residual psychotic symptoms involving disturbances in appearance, speech, behavior, perception, and thought that last for at least 6 months
• DSM-5 eliminated subcategories of schizophrenia (1).
• System(s) affected: central nervous system (CNS)

Epidemiology

• 7.7 to 43/100,000
• Predominant sex: male-to-female ratio = 1.4:1.0
• Age of onset: typically <30 years, earlier in males (early to mid-20s) than females (late 20s), with a smaller peak that occurs in women >45 years

• Lifetime (1%): highest prevalence in lower socioeconomic classes and urban settings (2-fold higher risk)
• 1.1% of the population >18 years old; similar rates in all countries

Etiology and Pathophysiology

• Stems from a complex interaction between genetic and environmental factors; higher incidence if prenatal infection or hypoxia, winter births, first-generation immigrants, advanced paternal age, drug use, and genetic (velocardiofacial) syndromes
• Overstimulation of mesolimbic dopamine D₂ receptors, deficient prefrontal dopamine, and aberrant prefrontal glutamate (NMDA) activity results in perceptual disturbances, disordered thought process, and cognitive impairments

Genetics
If first-degree biologic relative has schizophrenia, risk is 8–10% (a 10-fold increase).

General Prevention

• Currently, no known preventive measures decrease the incidence of schizophrenia.
• Interventions to improve long-term outcome and associated comorbid conditions are employed during management.

Commonly Associated Conditions

• Nicotine dependence (>50%) (1) and substance use disorders are common and lead to significant long-term medical and social complications.
• Metabolic syndrome, diabetes mellitus, obesity, and certain infectious diseases, including HIV, hepatitis B, and hepatitis C all occur in higher-than-expected rates in individuals with schizophrenia.