Insomnia as a risk factor for onset of depression in the elderly.

There are at least 9 studies that provide evidence that insomnia is a significant risk factor for recurrent and new onset major depressive disorder (MDD), two of which suggest that this association also exists specifically for the elderly. In this study, archival data from a community sample of healthy elderly participants were used to assess the extent to which insomnia predicts future illness in this age cohort. Out of the 147 participants with no prior history of mental illness, 66 participants were classified as having no insomnia, 47 had indeterminate insomnia, and 34 had persistent insomnia. Twelve participants developed MDD during the 1-year follow-up period. Two had no insomnia, 4 had indeterminate insomnia, and 6 had persistent insomnia. Persistent insomnia with onset of depression occurred only in female participants and was significantly associated with middle insomnia. These data suggest that elderly participants with persistent insomnia are at greater risk for the development of new onset depression.