Final answer:
Schizophrenia is more prevalent in identical twins than in fraternal twins, indicating a genetic component. Additionally, environmental factors interact with genetic predispositions, as evidenced by higher rates of schizophrenia among high-risk individuals in disturbed environments.
Step-by-step explanation:
The prevalence of schizophrenia is higher in identical (monozygotic) twins compared to fraternal (dizygotic) twins. This finding suggests that schizophrenia has a genetic component. Studies reveal that the risk of developing schizophrenia is significantly increased in individuals with a high genetic risk who are also raised in disturbed family environments, as opposed to those from healthy family environments or those with low genetic risk. Notably, a 2004 study found that the likelihood of adoptees with high genetic risk (biological mothers with schizophrenia) developing the disorder was 36.8% in disturbed environments and 5.8% in healthy environments, supporting the gene-environment interaction hypothesis.