AFFECTIVE-ILLNESS IN FAMILY MEMBERS AND MATCHED CONTROLS

As part of the US National Institute of Mental Health Collaborative Pr ogram on the Psychobiology of Depression study, a subset of 460 random ly chosen relatives of affectively ill probands were compared to a con trol group matched by the acquaintanceship method. The rate of major a ffective disorder in relatives was found to be 36%; the rate among con trols was 28%. Relatives were also found to have significantly higher rates of bipolar II disorder, any Research Diagnostic Criteria (RDC) a ffective disorder and any RDC mental disorder. All of these rates were found to be significantly higher when female relatives were compared with their acquaintances, but only the rate of any RDC mental disorder was higher when this comparison was made in men. The acquaintanceship method enabled the selection of a control group that closely resemble d the relatives, probably to the extent of ''overmatching''. When the match was evaluated to determine whether relatives tended to select co mparably ill (or well) acquaintances, this was found to be the case on ly for alcoholic and never mentally ill relatives.