Insomnia is an enormous burden in itself, but when combined with a mood disorder, the hardship it causes is multiplied and complicated through a feedback loop of suffering. Sleeping less, or poorly, worsens mood, which interferes with sleep, which heightens anxiety … and so on. And so you might ask: “Do sleep disorders cause mood disorders or vice versa?” Dr. David N. Neubaurer, associate director of the Johns Hopkins Sleep Disorders Center, replies.
Dr. Neubauer: That's not an easy question to answer. It is a relationship that goes both ways. There is very clear evidence that when a person is experiencing a mood disorder, particularly a major depressive episode, he or she is highly likely to suffer from sleep disturbance -- most often, insomnia. In fact, it is so expected that it's part of the diagnostic criteria in the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV).
When surveying people who are depressed, we find that 80% experience insomnia, and it's not only the classic early-morning awakening associated with depression, but rather all the possibilities, including difficulty falling asleep and middle-of-the-night awakenings. There is also the issue of severity: The more depressed someone is, the more likely it is that he or she will have insomnia.
The converse is true, too. If a person suffers from insomnia, over time it creates a risk for developing a mood disorder such as major depression. There are several excellent observational studies that demonstrate the link between insomnia and the future risk of developing a mood disorder. The link is evident as quickly as one year after an episode of insomnia, and can last as long as decades.
Regardless of which comes first, there is a lot of comorbidity (coexistence) between insomnia and depression, and it's important to address both conditions. One of the greatest challenges in depression is to find the medication (or combination of medications) that will alleviate the depression as well as the insomnia.
