Depression and manic depression are associated with dementia, and the more often a patient is hospitalized for these mental illnesses the greater their risk, Danish researchers report.

The study involved an analysis of all hospital admissions for mental illnesses that took place in Denmark between 1970 and 1999. The study included 18,726 patients with depression and 4248 with manic depression, also called bipolar disorder.

Dr. L. V. Kessing and Dr. P. K. Andersen, from the University of Copenhagen in Denmark, report their findings in the Journal of Neurology, Neurosurgery, and Psychiatry.

As noted, the risk of dementia increased as the number of hospitalizations for these mental illnesses rose. For patients with depression and those with bipolar disorder the rate of dementia increased by 13 and 6 percent, respectively, for each episode resulting in admission.

“The study supports the possibility of a direct association between (these mental illnesses) and dementia,” the authors note. “If our results can be confirmed in future studies they underscore the importance of early (treatment of) depressive and bipolar disorders,” they add.

SOURCE: Journal of Neurology, Neurosurgery, and Psychiatry, December 2004.