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When people are deprived of sleep, the first and most salient effects are mood changes – we become irritable and the daily grind feels harder.Getty Images/iStockphoto

Depressed? Can't sleep? Or should I say: Can't sleep? Depressed? New research findings are turning old beliefs about the depression-sleep connection on their head.

When people are deprived of sleep, the first and most salient effects are mood changes – we become irritable and the daily grind feels harder. Take these mood symptoms up a notch in intensity and duration and you have what's called clinical depression or major depressive disorder.

Major depressive disorder is characterized by low mood and/or loss of interest in activities, which co-occur with symptoms such as feelings of worthlessness, difficulty concentrating, reduced appetite, sleep difficulty, fatigue and suicidal thoughts.

In the past, clinicians who treated clinical depression viewed sleep difficulty as a tag-along symptom of the mood disorder. The approach was to treat the depression as the main problem and hope that the insomnia took care of itself.

However, often the insomnia did not clear up on its own, persisting after the person's mood improved and sometimes forecasting a recurrence of depressed mood. Now, results of two lines of research are converging to suggest that sleep plays a prominent role in the development of depression and that the treatment of sleep can play a key role in recovery.

Insomnia increases the risk of developing depression

Researchers who have followed people with insomnia over months and years have found that (non-depressed) people who have insomnia are more likely than those without insomnia to subsequently develop major depression.

More than 20 studies have found this relationship and their findings were combined in a meta-analysis by Chiara Baglioni from the University of Freiburg in Germany and her colleagues. This meta-analysis, published in Journal of Affective Disorders in 2011, showed that, on average, having insomnia doubled the likelihood of becoming clinically depressed within the next few years (the average duration of follow-up was six years). The notion of insomnia only being a tag-along symptom of depression is in question now because here we have evidence of insomnia being a forerunner of depression.

Treating insomnia elevates mood

Researchers are finding that treating insomnia has the pleasant side-effect of enhancing mood.

Rachel Manber at Stanford University and colleagues found that the mood of patients is lifted when their insomnia is treated using cognitive behavioural therapy for insomnia, or CBT-I, a non-drug treatment (in the Journal of Clinical Sleep Medicine in 2008 and in the journal SLEEP in 2011).

A study recently published in SLEEP from the Karolinska Institute in Stockholm by Kerstin Blom and colleagues compared Internet-delivered CBT-1 to Internet-delivered cognitive behaviour therapy for depression (an effective psychological treatment for depression) for patients who had both major depression and insomnia. The patients were randomly assigned to one of the two treatments.

The data showed that not only did the CBT-I treatment lead to superior improvements in sleep, but it also led to improvements in mood that were at least as large as those associated with the depression-specific treatment.

This suggests that treating the insomnia may be just as effective, or possibly more effective, than treating the depression itself. Another recent study showed that treating insomnia in more than 400 American veterans using CBT-I improved their sleep as expected, but was also associated with a reduction in suicidal ideation, a feature of some cases of depression.

In Canada, Colleen Carney at Ryerson University is working to improve the treatment and prevention of chronic insomnia and depression. As she says on her website, "Improving sleep in those with depression produces far greater depression recovery rates than our current approach to depression, which is to treat the depression alone, so our results may directly improve depression treatment."

This type of research has opened up new avenues to our understanding of depression and the importance of sleep to our emotional well-being. Perhaps in the future, mood disorders will be treated or prevented by using sleep interventions.

It's too early to recommend using CBT-I alone for depression, but if you are depressed and have insomnia, it can't hurt to go ahead and use CBT-I to treat the insomnia. This will improve your sleep and may also help your mood.

Dr. Judith R. Davidson is a clinical psychologist and sleep researcher. She works with the Kingston Family Health Team and Queen's University at Kingston. She is the author of Sink into Sleep: A Step-by-Step Workbook for Reversing Insomnia. You can follow her on Facebook and on Twitter at @JudithRDavidson

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