The findings of 2 studies suggest that chronic insomnia may trigger and prolong depression among the elderly population. The first study followed the mental health of >1800 men and women over the age of 65 diagnosed with severe and/or mild depression. Once the researchers determined whether or not the participants had persistent insomnia, the patients were evaluated twice, first at 6 months and then after 1 year, for markers of depressive illness.
The results of the study showed that individuals who experienced insomnia were almost 11 times more likely to continue being depressed after 6 months. Furthermore, they were 17 times more prone to be depressed after a year, compared with patients without insomnia.
The second study included 147 men and women over the age of 60 with no history of mental illness at the study's onset. Of the participants, 34 experienced persistent insomnia, 47 had less persistent "indeterminate insomnia," and 65 had no sleep problems. After conducting 2 tests over a 1-year period, the investigators discovered that 12 patients experienced newonset depression during the time frame. Of the newly depressed patients, half experienced persistent insomnia, 4 had indeterminate insomnia, and 2 had no sleep problems.
Patients with persistent insomnia and most at risk for depression were the "middle insomniacs," characterized by sleep patterns that were usually disturbed by waking up in the middle of the night. The researchers concluded that patients with persistent insomnia are 6 times more likely to exhibit serious new-onset depression, compared with individuals who rest easily.