Schizophrenia

Schizophrenia is a complex mental disorder marked by significant disturbances in perception, thought processes, emotional expression, and behaviour. It typically emerges in late adolescence or early adulthood and follows a varied course that may involve episodes of psychosis, long-term functional impairment, or, in a proportion of cases, substantial improvement over time. Diagnosis relies on clinical assessment rather than laboratory testing and incorporates reported experiences, observed behaviour, and collateral information from those familiar with the individual.

Epidemiology and Risk Factors

Globally, schizophrenia affects approximately 0.3–0.7% of the population during their lifetime. In 2022, an estimated 24 million people were living with the condition, and around 1.1 million individuals developed it for the first time in 2017. Males are diagnosed more frequently and tend to experience earlier onset than females.
Genetic predisposition plays a major role, with both common and rare genetic variations contributing to risk. Environmental influences also increase susceptibility, including urban living, childhood trauma, adolescent cannabis use, prenatal malnutrition, advanced paternal age, and certain infections. The interaction of hereditary and environmental factors is considered central to the development of the disorder.

Clinical Course and Outcomes

The long-term course of schizophrenia varies widely. About half of those diagnosed experience notable improvement with minimal relapses, and a small proportion recover completely. The remaining individuals typically show persistent symptoms and functional limitations. Severe cases may require hospitalisation, while social difficulties such as unemployment, poverty, and homelessness frequently accompany the disorder.
People with schizophrenia have elevated physical health risks, including cardiovascular disease and metabolic complications, resulting in a 20–28 year reduction in life expectancy. Suicide occurs in roughly 5% of cases. In 2015, approximately 17,000 deaths worldwide were linked to schizophrenia.

Positive Symptoms

Positive symptoms refer to experiences or behaviours not ordinarily present in healthy individuals. These include hallucinations, delusions, disorganised thinking, and disturbed behaviour or emotional expression. Hallucinations occur in up to 80% of patients at some point, most often auditory verbal hallucinations. Multisensory hallucinations may also appear and tend to show thematic links with delusional beliefs.
Delusions often take persecutory or referential forms and may include experiences of thought insertion, thought withdrawal, or thought broadcasting. These phenomena are sometimes classified as disorders of the self. Positive symptoms generally respond well to antipsychotic medication and may diminish over the lifespan.

Negative Symptoms

Negative symptoms are deficits of normal emotional or cognitive functions and are among the most disabling aspects of schizophrenia. Five core domains are recognised:

• Blunted affect: reduced or flat emotional expression
• Alogia: impoverished speech output
• Anhedonia: inability to experience pleasure
• Asociality: lack of desire for social interaction
• Avolition: reduced motivation or goal-directed behaviour

These symptoms can be broadly divided into apathy/lack of motivation and diminished expression. Apathy, including anhedonia and avolition, is the most prominent subdomain and strongly correlates with impaired functional outcomes. Negative symptoms may be primary to schizophrenia or secondary to other influences such as medication side effects, active psychosis, or social deprivation. While generally less responsive to medication, targeted psychosocial and pharmacological strategies may improve secondary symptoms.
Assessment tools such as the Clinical Assessment Interview for Negative Symptoms (CAINS) and the Brief Negative Symptom Scale (BNSS) provide structured measures of severity and domain-specific deficits.

Cognitive Symptoms

Cognitive impairment affects around 70% of people with schizophrenia and may appear years before the onset of psychosis. Difficulties commonly involve memory, attention, processing speed, planning, and problem solving. These deficits are key predictors of functional outcomes and quality of life. Early-onset and late-onset forms of the disorder often display more pronounced impairments. Cognitive weaknesses may also reflect disrupted neural connectivity affecting multiple brain regions.

Diagnosis

Diagnosis is established according to criteria in the DSM-5 or ICD-11. DSM-5 requires symptoms to persist for at least six months, whereas ICD-11 stipulates one month. The process incorporates evaluation of positive, negative, and cognitive symptoms, functional impairment, and exclusion of other psychiatric or medical conditions. Co-occurring disorders—such as mood disorders, anxiety disorders, substance use disorders, and obsessive–compulsive disorder—are common and complicate clinical assessment.

Treatment Approaches

The primary treatment for schizophrenia is antipsychotic medication, with drugs such as risperidone and olanzapine frequently used. Around one-third of patients do not respond adequately to first-line agents; for these individuals, clozapine is recommended and is generally the most effective antipsychotic, though it carries a higher risk of significant side effects.
Psychotherapy, supported employment, social skills training, and rehabilitation programmes are critical to improving functional outcomes. In acute phases where an individual presents a risk of harm to self or others, short-term involuntary admission may be necessary. Long-term hospitalisation is uncommon in high-resource settings but may occur where community services are limited.

Social and Public Health Considerations

Schizophrenia imposes considerable social and economic burdens. People affected often face stigma, discrimination, and reduced access to education and employment. Homelessness, social isolation, and vulnerability to exploitation are disproportionately common. Efforts to improve community support, access to healthcare, and early intervention services remain essential to reducing the long-term impact of the disorder.