Final answer:
The likelihood of developing schizophrenia increases if a sibling has it due to genetic factors, but environmental factors also play a crucial role. One parent with the disorder increases the risk for their child, and having both parents with schizophrenia further raises the likelihood.
Step-by-step explanation:
The likelihood of developing schizophrenia if a sibling has the condition increases compared to the general population, as schizophrenia has a genetic component. When one parent has schizophrenia, your chances of developing the disorder are higher still. In cases where both parents are diagnosed with schizophrenia, the likelihood that their children will develop the condition increases even more. However, genetics is not the sole factor in determining whether a person will develop schizophrenia. Environmental factors, including being raised in a disturbed family environment, can significantly increase the risk for those with a genetic predisposition.
Studies have shown that adoptees with high genetic risk (biological mother with schizophrenia) and raised in disturbed family environments have a particularly high likelihood of developing schizophrenia, up to 36.8%. However, if the family environment is healthy, this risk lowers to 5.8%. This underscores the importance of both genetic and environmental factors in the development of schizophrenia.