CONTINUITY AND DISCONTINUITY OF AFFECTIVE-DISORDERS AND SCHIZOPHRENIA- RESULTS OF A CONTROLLED FAMILY STUDY

Background: It is widely acknowledged that the genetic diatheses for s chizophrenia and affective disorders are independent. However, there a re increasing doubts about this classic view, and empirical evidence f or a dichotomy of these two prototypes of functional psychoses is limi ted. A controlled family study of consecutive admissions was conducted to determine whether familial risks for schizophrenic (SCZ) and affec tive disorders were independent or overlapping. Methods: Index proband s met Research Diagnostic Criteria for SCZ (n=146), schizoaffective (S A [n=115]), bipolar(BP [n=80]), or unipolar major depressive (UP [n=18 4]) disorder. Comparison probands met Research Diagnostic Criteria for alcoholism (n=64) or were sampled from the general population (n=109) . A total of 2845 first-degree relatives were blindly diagnosed from i nterview, informant, and/or record data, with direct interviews comple ted in 2070 (82% of living first-degree relatives). Results: By Cox's proportional hazards analysis, SCZ, SA, BP, and UP disorders were fami lial, in that each group of relatives had an increased lifetime morbid risk (vs those with alcoholism and those from the general population) for the proband's diagnosis. The SCZ and BP disorders were transmitte d independently: only probands with manic disorders (BP or SA-BP subty pe) showed increased familial risks of BP disorder, and only probands with prominent SCZ features (SCZ or SA) showed increased familial risk s of SCZ disorder. However, SCZ probands had an increased familial ris k for UP disorder (as did SA, BP, and UP probands) and for the SA-UP s ubtype. Aggregation of depression in families of SCZ probands could no t be explained by the subtype of depression, broad or narrow definitio n of SCZ disorder, presence or absence of history of depression in SCZ probands, whether onset of depression in a relative occurred before o r after onset of a proband's SCZ disorder, or assortative mating. Conc lusions: These data suggest that there could be a familial relationshi p between the predispositions to schizophrenia and to major depression . We discuss a number of alternative hypotheses about the nature of th is possible relationship.