People with depression frequently have trouble sleeping and this restlessness often first appears at the onset of the depressive disorder and continues until well after the depression has been successfully treated.

This new meta-analysis conducted by a research team from the University of Freiburg Medical Center in Germany, investigates if insomnia can be viewed as a predictor of depression. The researchers conducted a systematic search to identify longitudinal epidemiological studies simultaneously investigating insomniac complaints and depression. They found 21 studies to include in their analysis. Considering all studies together, heterogeneity was found. They used the odds ratio for insomnia to predict whether or not depression was likely.

Here’s what they found:

• Non-depressed people with insomnia have a two-fold risk of developing depression, compared to people with no sleep difficulties
• The random-effects model showed an overall odds ratio for insomnia to predict depression of 2.60 (confidence interval [CI]: 1.98-3.42)
• When the analysis was adjusted for outliers, the studies were no longer heterogeneous
• The fixed-effects model showed an overall odds ratio of 2.10 (CI: 1.86-2.38)

The authors concluded:

Early treatment programs for insomnia might reduce the risk for developing depression in the general population and be considered a helpful general preventive strategy.

Baglioni C, Battagliese G, Feige B, Spiegelhalder K, Nissen C, Voderholzer U, Lombardo C, Riemann D. Insomnia as a predictor of depression: a meta-analytic evaluation of longitudinal epidemiological studies. J Affect Disord. 2011 Dec;135(1-3):10-9. Epub 2011 Feb 5. [PubMed abstract]