For some time there has been felt to be an association between a history of depression and eventual development of dementia. Two new studies add weight to that association, as reported in today’s BBC News (http://news.bbc.co.uk/2/hi/health/10507074.stm).
The first study followed a group of older adults and found that development of depression increased the subsequent risk of dementia from 17% to 22% during the study. The second study showed that earlier episodes of depression were associated with increased risk, which nearly doubled if two or more episodes of depression occurred.
Of course, an association does not prove cause-and-effect. Many questions are raised: Does depression affect brain chemistry, producing inflammation or damaging proteins in the brain? Do people who are depressed isolate themselves from society, which may also contribute to cognitive decline? Does successful treatment of depression lower the risk? How about the studies that show cognitive-behavioral approaches are equal to drug therapy for depression? And what about seasonal affective disorder – does that count?
It has previously been thought that untreated depression caused a higher risk, but these results should prompt more studies to examine the connection further. In the meantime, depression should not be taken lightly and people with suggestive symptoms should seek help, if for no other reason than to feel better.