Single or multiple familial cognitive risk factors in schizophrenia?

The fact that relatives schizophrenia display abnormalities suggests geneti c transmission of an underlying cognitive endopheno-type. It was examined t o what extent the cognitive abnormalities that discriminate patients and re latives from controls do so independently of each other, and independent of IQ, Neuropsychological measures were assessed in 50 patients with schizoph renia, 50 first-degree relatives of patients with schizophrenia, and 50 hea lthy controls. The assessment focused on episodic memory, attentional span, simple and complex speed of information, and semantic memory. Factor analy sis of the cognitive test results yielded four factors reflecting speed, ep isodic memory, working memory, and semantic fluency, Performance of the rel atives was intermediate to that of the patients and the controls after adju stment for age, sex, educational level, and IQ, For both patients and relat ives, speed of information processing, working memory, and episodic memory independently discriminated from control performance, with a similar patter n in the order of the size of the effects. The results suggest the existenc e of more than one familial cognitive risk factor for schizophrenia. Indepe ndent familial cognitive risk factors may represent separate causal influen ces or separate indicators of risk related to the same genetic mechanism. ( C) 2001 Wiley-Liss, Inc.