There are many types of mental illnesses, some of which have little to do with heredity and are often related to brain diseases or other diseases of the body, such as cerebral thrombosis, brain tumors, traumatic brain injury, serious infections, and poisoning. For mental illnesses currently considered to be genetically related, genetic factors only play a role. In schizophrenia and depression, for example, more than half a century of research has confirmed that genetic factors play an important role in the development of schizophrenia, with a risk rate of 4%-14% among first-degree relatives suffering from the disease, about 10 times that of the general population. In secondary relatives of patients, the risk rate is about three times higher than that of the general population. In a survey of depressed patients, it was found that about 40-70% of patients have a genetic predisposition, i.e., nearly or more than half of patients can have a family history of depression, so the risk of depression in relatives of depressed patients, especially first-degree relatives, is significantly higher than in the general population. In conclusion, family members may have a higher chance of developing mental illness than the general population, and the closer the relatives, the higher the prevalence.