To the Editor. —
Family history is often used to support diagnostic formulations. Using the validation criteria of treatment response, course of illness, and family history for differentiating schizophrenia from affective illness, Pope and Lipinski1 presented a convincing argument regarding the common practice of underdiagnosing affective illness and overdiagnosing schizophrenia. If a patient with a family history of affective illness meets DSM-III criteria for schizophrenia, should the diagnosis be reconsidered based on the family history?The answer is no, based on the data presented recently by Kendler et al.2 They examined the risk for various psychiatric diagnoses using DSM-III criteria in 723 first-degree relatives of schizophrenic patients and in 1056 first-degree relatives of matched Surgical controls. Affective disorders were nearly three times more frequent than was schizophrenia in the firstdegree relatives of schizophrenic probands (prevalence was 7.0% for affective disorders vs 2.7% for schizophrenia; corrected for differential mortality).