1. (1) to identify the proportion of families that have at least one first degree relative (FDR) with major unipolar depression (MUD), across bipolar (BP) and schizophrenic (SC) multiplex families;

2. (2) to assess if there are significant demographic/clinic differences between these two groups.

The sample included 120 families with at least one first or second degree proband relatives diagnosed with BP or SC disorders. We selected BP and SC probands’ families that had at least one FDR with MUD, according to DSM-III-R. All families have been evaluated with Diagnostic Interview for Genetic Studies and selected according to the diagnostic definitions of DSM-III-R, based on the Operational Criteria Checklist. T-tests and chi-square tests used to analyze demographic and clinical differences between the two groups.

Out of the 60 BP families, 38.3% had at least one FDR with MUD; depressed relatives were predominantly female (68.7%) - sisters (35.5%), mothers (29%), daughters (3.2%). The average age of onset and length of illness was 35 and 15 years, respectively. Out of 60 SC families, 31.6% had at least one FDR with MUD; the majority of depressed relatives were females (81.8%) - sisters (42.9%), mothers (38%) daughters (4.8%). The average age of onset and length of illness was 30 and 19 years, respectively. There was no significant statistical differences between BP and SC families.

These results may support the thesis of a common genetic vulnerability to MUD, and the continuum viewpoint of affective and psychotic disorders.