Schizophrenia is a complex mental disorder influenced by both genetic and environmental factors, and it is not passed down by just one parent. Neither the mother nor the father is solely responsible inheritance occurs through a combination of genes from both parents.

Genetic Contribution

• Schizophrenia has a strong hereditary component, with heritability estimated at 70–80% based on twin and family studies (Sullivan et al., Archives of General Psychiatry, 2003).
• No single gene causes schizophrenia. Instead, it results from multiple genetic variants (polygenic risk) interacting with each other and environmental triggers.
• Children of a parent with schizophrenia have a ~10% risk of developing it (vs. 1% in the general population), but this risk comes from inherited DNA from both parents, not one exclusively.
• Identical twins share 100% of genes: if one has schizophrenia, the other has a 40–50% chance of developing it far higher than fraternal twins (~10%), confirming genetics but also showing non-genetic factors matter.

Maternal vs. Paternal Influence

• No evidence shows one parent contributes more genetically. Risk is comparable whether the affected parent is the mother or father (Gottesman, Schizophrenia Genesis, 1991).
• Maternal factors like prenatal infections, stress, or malnutrition can increase risk via epigenetic changes or brain development issues but these are environmental, not direct genetic transmission from the mother.
• Paternal age (>40) slightly raises risk due to de novo mutations in sperm, but this is a minor factor and not "passing down" the disorder in the traditional sense.

Key Takeaway

Schizophrenia risk is shared equally through genes from both parents, amplified by environment. If one parent has schizophrenia, genetic counseling can help assess risk, but most children will not develop the disorder. Early intervention and monitoring are key for at-risk individuals.