Schizophrenia is caused by a complex interplay of genetic, environmental, and neurobiological factors, rather than a single known cause.
Genetic Factors
- Schizophrenia tends to run in families, indicating a strong genetic component. Studies show that genetics can explain about 80% of the risk
- No single gene causes schizophrenia; instead, multiple genes contribute modestly to the risk. Some rare mutations, like the chromosome 22q11.2 deletion, significantly increase risk
- Twin studies reveal that if one identical twin has schizophrenia, the other has about a 50% chance of developing it, while for non-identical twins, the risk is about 12.5%
Brain Structure and Chemistry
- People with schizophrenia often show subtle differences in brain structure and development, although these changes are not present in all cases and can occur in people without the disorder
- Neurotransmitter imbalances, especially involving dopamine and possibly serotonin, play a key role. Medications that reduce dopamine activity can alleviate symptoms, indicating dopamine's involvement
Environmental and Developmental Factors
- Complications during pregnancy and birth, such as low birth weight, premature labor, or oxygen deprivation, may subtly affect brain development and increase schizophrenia risk
- Exposure to viruses or toxins in the womb is also considered a possible risk factor
Psychological and Social Triggers
- Stressful life events like bereavement, abuse, loss of job or home, and other major emotional stresses can trigger schizophrenia in people who are already vulnerable
- Drug abuse, particularly cannabis (especially high-potency forms), cocaine, LSD, and amphetamines, is linked to an increased risk of developing schizophrenia or triggering relapse in those with the condition
Summary
Schizophrenia results from a combination of inherited genetic vulnerabilities and environmental influences that affect brain development and function. Stressful life events and substance use can act as triggers in susceptible individuals, but no single cause explains all cases
