Since E. Kraepelin isolated schizophrenia and bipolar disorder as heterogeneous diseases, attempts to categorize mental illnesses have continued to the DSM-5. Meanwhile, cases of psychosis occurring as a result of neurosyphilis have been reported. Whilst in some cases it is useful to divide mental illnesses, in others imposing such classifications may be not be feasible. Since 2008 numerous papers have been published showing that the same genes are related to an increased incidence of several psychiatric diseases including intellectual disorder, autism, ADHD, schizophrenia, bipolar disorder, and depression. This suggests that the theory that these are separate and heterogeneous diseases should be rejected. Aside from the categorical classification in the DSM, it is desirable to create new diagnostic criteria that capture mental illness as a spectrum.