Epidemiological and clinical correlates of familial and sporadic schizophrenia.

We studied 68 schizophrenic cases with a schizophrenic first-degree relative (familial group) and 62 cases without such a family history (sporadic group). We compared them on: (i) clinical variables, including premorbid adjustment, age of onset and severity of symptoms; (ii) neural abnormalities, including abnormal involuntary movements, neural "soft" and "hard signs"; (iii) neuropsychological tests, including the Wechsler Adult Intelligence Scale and the Continuous Performance Test and (iv) environmental risk factors, including winter birth and obstetrical complications. Sporadic cases were more likely to be born in winter and had more severe psychotic symptoms, but most analyses yielded no difference between the groups. Our results offer some support that sporadic schizophrenia is a more environmental subtype, but they also suggest that the familial vs sporadic distinction of schizophrenia has limited power to identify distinct subgroups.