Psychiatric disorders in relatives of subjects with Alzheimer's disease. No evidence for common genetic risk factors.

INTRODUCTION: The clustering of two or more disorders in the same family might indicate the presence of common genetic risk factors. The prevalence of various psychiatric disorders in relatives of Alzheimer's disease (AD) patients has rarely been investigated. Consequently, family study data were reinvestigated to assess, if there are indications for an overlap of genetic risk factors of AD and other psychiatric disorders. METHOD: Family history information on 2964 living and deceased first-degree relatives of 146 AD patients, 168 patients with major depression (MD) and 136 control subjects were obtained by at least one informant. Of the living relatives, 49.2 % could also be interviewed. Best-estimate lifetime diagnoses were made on all available information. Lifetime prevalences of psychiatric disorders were compared in relatives of AD patients, of MD patients and of control subjects using chi(2) statistics. Cox proportional hazards regression analyses were additionally performed to control for the relative's age, gender and source of information (interview vs. family history information). RESULTS: Relatives of AD patients had no increased risk of other psychiatric disorder compared with relatives of the comparison groups. CONCLUSION: AD is genetically distinct from other psychiatric disorders, i. e., schizophrenia, anxiety, obsessive-compulsive, somatoform disorders, alcoholism, substance abuse or dependency.