Simple schizophrenia: an investigation of Bleuler's criteria based on the major twin studies of schizophrenia.

Schizophrenics fulfilling Bleuler's criteria for simple schizophrenia--no evidence of hallucinations, delusions, and catatonic behavior--were similar to schizophrenics with more typical forms of the disorder with respect to negative symptoms, premorbid social adjustment, and age at onset. These results support the validity of the simple schizophrenia subtype by providing evidence that schizophrenics without conspicuous positive symptoms are similar to those with such symptoms on these core features of the disorder.