A STUDY OF FAMILIAL AGGREGATION OF DEPRESSION, DEMENTIA AND PARKINSONS-DISEASE

Depression is often accompanied by other disorders including Alzheimer 's disease and Parkinson's disease. We studied the familial aggregatio n of these disorders in order to examine the possibility of a shared g enetic origin. In a population-based study of 6596 subjects, we studie d the association of self-reported depression, which required treatmen t by a psychiatrist, to family history of psychiatric disease, dementi a, and Parkinson's disease. A family history of psychiatric disease wa s significantly associated with overall depression as well as with uni polar (n = 303 patients) and bipolar (n= 27 patients) depression. The risk of unipolar depression was associated with the presence of two or more demented individuals among their first degree relatives (e.g. pa rents, siblings and children). Since there was no evidence for familia l aggregation in subjects with only one demented relative, our study s uggests that unipolar depression may be associated specifically to a s trongly familial, form of dementia. The risk of bipolar depression was in creased for those with one or more relatives with dementia and, pe rhaps, for those with relatives with Parkinson's disease. The familial aggregation of depression with dementia and perhaps Parkinson's disea se suggests that there may be shared susceptibility gene(s) underlying these diseases. Our study indicates further that there may be differe nces in the genetic etiology between unipolar and bipolar depression.