Not all mental illnesses are hereditary: There are many types of mental illnesses, some of which have little to do with heredity and are often associated with brain disorders or with other disorders of the body, such as cerebral thrombosis, brain tumors, traumatic brain injury, serious infections, and poisoning. Even for psychiatric disorders currently considered to be genetically related, genetic factors play only a minor role. In the case of 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. The risk rate of having the disease among first-degree relatives is 4-14%, about 10 times that of the general population, and if both parents suffer from schizophrenia, the risk rate can be as high as 40%. 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.