Description

• Major psychiatric disorder with a variable course, typically involving prodromal, active, and residual psychotic symptoms with disturbances in thought, speech, affect, behavior, and perception
• DSM-5 eliminated subcategories of schizophrenia (paranoid, disorganized, catatonic, etc.).
• System(s) affected: central nervous system (CNS)

Epidemiology

Incidence

• 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 (late teens to mid-20s) than in females (early 20s to early 30s), with a smaller peak that occurs in women >45 years; more subtle changes in cognition and functioning can precede the diagnosis (prodromal period) by several years.

Prevalence

• 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

Educate all patients on the risks around marijuana use, especially those in a potential prodromal period or those with a family history of psychosis.

Commonly Associated Conditions

• Nicotine dependence (>50%) and substance use disorders
• Metabolic syndrome, diabetes mellitus, obesity, and infectious diseases, including HIV, hepatitis B, and hepatitis C all occur in higher-than-expected rates.