Medically reviewed by Dr. Alicia Moreno, PhD
Co-Occurring Disorders Editor & Mental Health · Last reviewed January 2025

Schizophrenia is a severe, chronic mental disorder affecting approximately 0.25–0.64% of the U.S. population, according to the NIMH. Despite its relatively low prevalence, schizophrenia accounts for a disproportionate share of psychiatric disability and healthcare utilization. It typically emerges in late adolescence to early adulthood, with earlier onset in men (late teens to early 20s) than women (mid-20s to early 30s).

Symptoms

Positive Symptoms

Positive symptoms represent experiences added to baseline functioning — things that are present that shouldn't be:

Delusions — Fixed, false beliefs not amenable to reason or evidence (e.g., persecutory delusions, grandiose delusions, ideas of reference)
Hallucinations — Perceptions without external stimuli; auditory hallucinations (hearing voices) are most common
Disorganized thinking — Manifested in speech as loose associations, tangentiality, or incoherence
Grossly disorganized or catatonic behavior

Negative Symptoms

Negative symptoms represent diminutions in normal functioning — things that are absent that should be present. They are often more treatment-resistant and functionally disabling than positive symptoms:

Affective flattening — Reduced emotional expression
Alogia — Poverty of speech
Avolition — Reduced motivation and goal-directed activity
Anhedonia — Reduced capacity for pleasure
Asociality — Reduced desire for social interaction

Schizophrenia and Substance Use

Substance use disorders are extraordinarily common in schizophrenia — estimated prevalence of comorbid SUD is approximately 47%. Cannabis use is particularly concerning in schizophrenia: it can precipitate psychotic episodes in vulnerable individuals, worsen positive symptoms, and reduce antipsychotic efficacy. The relationship between cannabis and schizophrenia is an active area of research, with growing evidence that high-potency cannabis use is associated with increased psychosis risk in genetically vulnerable individuals. See our article on schizophrenia and substance use.

Treatment

Antipsychotic Medications

Antipsychotic medications are the cornerstone of schizophrenia treatment and the primary intervention for acute psychosis. Second-generation (atypical) antipsychotics — including olanzapine, risperidone, quetiapine, aripiprazole, clozapine, and others — are generally preferred over first-generation agents for most patients due to a more favorable side-effect profile regarding extrapyramidal symptoms.

Clozapine is the most effective antipsychotic for treatment-resistant schizophrenia, with evidence of efficacy in approximately 30–60% of treatment-resistant patients. Its use requires regular blood monitoring due to the risk of agranulocytosis.

Long-acting injectable antipsychotics (LAIs) are an important option for patients with adherence challenges — eliminating the need for daily oral medication and providing consistent blood levels.

Psychosocial Interventions

Pharmacotherapy alone is insufficient for optimal outcomes in schizophrenia. Evidence-based psychosocial interventions include Coordinated Specialty Care (CSC) for first-episode psychosis, Assertive Community Treatment (ACT) for severely ill individuals with frequent hospitalizations, cognitive remediation therapy for cognitive deficits, and supported employment programs (Individual Placement and Support model).