Insomnia may pave the way for depression rather than occur primarily as a symptom of the disorder, according to two University of Rochester Sleep and Neurophysiology Research Laboratory (SNRL) studies--one slated to appear in the Journal of Behavioral Sleep Medicine and another presented at the Associated Professional Sleep Societies (APSS) 19th Annual Meeting in June.
The studies bolster other evidence that insomnia is a significant risk factor for recurrent and new onset major depressive disorder, according to the researchers.
"We need to think of [insomnia] as both a symptom and a primary disorder," says psychologist Michael L. Perlis, PhD, lead researcher of one of the studies and SNRL director. "Too many people think insomnia is insomnia is insomnia...the evidence to date is that the story is more complicated than that."
In the study published in the Journal of Behavioral Sleep Medicine, Perlis and his colleagues found that adults older than 60 with persistent insomnia were nearly six times more likely to develop a first episode of major depression than were seniors without insomnia. The association was strongest among women and people who suffer from a particular insomnia pattern that causes people to wake repeatedly during the night.
To reach this finding, Perlis and his colleagues used archival data from a 2002 longitudinal study that measured depressive disorders and symptoms in older primary-care patients. The original researchers, led by Jeff Lyness, MD, evaluated 247 participants, 60 to 94 years old, twice in one year for depression using the Structured Clinical Interview for DSM-III-R (SCID) and the Hamilton Rating Scale for Depression.
Perlis and his colleagues then aggregated and categorized the data. They found that seniors with insomnia were more likely to develop a first episode of major depression compared with those with no insomnia.
In the study presented at the APSS Annual Meeting, another member of the SNRL group, Wil Pigeon, PhD, found that depressed seniors with insomnia were eight to 12 times more likely to remain ill compared with patients with no insomnia. In addition, those with persistent insomnia were at greater risk for the development of another depressive episode.
To reach these findings, the researchers used data from a clinical trial that assessed the outcome of Improving Mood-Promoting Access to Collaborative Treatment, a program that looks at late life depression in primary care. The original researchers interviewed 1,801 participants with depression. The researchers diagnosed the participants using SCID and assessed the severity of the depression using Symptom Checklist 90.
They found that, in addition to being a predisposing and prodromal sign of depression, insomnia may dull depression treatment and serve as a barrier to remission.
Although the association is likely to be mediated by a variety of factors, Perlis believes that insomnia may precede depression, in part, because both conditions involve the activation of the depressive schema, like feelings of hopelessness and lack of control.
While both studies focused on seniors, Perlis says, the findings for the new onset data are applicable to young adults and middle-age people with chronic insomnia.
"It is increasingly clear that you can't hope that chronic insomnia will just go away of its own accord or with treatment for the 'parent disorder,'" he says. "You have to treat it with interventions that specifically target insomnia, such as cognitive-behavioral therapy for insomnia."
To help put their findings into practice, Perlis and his colleagues aim to recruit clinical psychologists to undergo training and certification to treat insomnia.