Diathesis-Stress Theory states that psychological disorders develop due to a combination of genetic vulnerability and risk factors in the environment.
Let’s say someone inherited genes that put them at risk for schizophrenia. According to the diathesis-stress model of schizophrenia, the at-risk person might avoid developing the disease if stress in their life is low. But high levels of stress could trigger onset of the disease. Possible environmental stressors include family conflict, abuse, trauma, problems at school, rejection by peers, and even poor nutrition.