From the Journals

Novel analysis links insomnia to first-onset major depressive disorder



Severity of insomnia, specifically difficulty initiating sleep, was a significant predictor of major depressive disorder, a prospective study of 768 adults with a history of depression suggests.

Insomnia has been identified as a risk factor for depression, but the impact of lifetime depression history and the role of insomnia in major depressive disorder (MDD) remains unclear, wrote Tessa Blanken, MSc, of the Netherlands Institute for Neuroscience, Amsterdam, and colleagues. Studies of this relationship have been hampered by the difficulty of isolating the impact of insomnia as an independent predictor of MDD from depression and other disorders.

In a study published in Sleep, the researchers reviewed data from 768 adults aged 18-65 years who were participants in the Netherlands Study of Depression and Anxiety, a multicenter, longitudinal study that included four assessments over 6 years. The participants had no current or prior diagnosis of MDD. The average age of the participants was 41 years, and 63% were women.

The investigators used Network Outcome Analysis to study the link between insomnia and MDD. The investigators wrote, “Network modeling techniques provide a unique framework to study the interactions among symptoms and their role in the development and maintenance of psychiatric disorders. Using network analysis we can estimate the unique association between pairs of symptoms, while controlling for the state and associations of all other symptoms.”

Over 6-years’ follow-up, 141 participants (18%) were diagnosed with first-onset MDD. Overall, insomnia severity was a significant predictor of first-onset MDD (hazard ratio 1.11, 95% confidence interval). The analysis showed that the predictive effect of insomnia on first-onset MDD was driven solely by the item “Did you have trouble falling asleep” (hazard ratio, 1.33; 95% confidence interval, 1.12-1.57; observed range, 0-4). Those individuals who had trouble falling asleep 3-4 times or more than 4 times a week were 2.3 or 3.2 times, respectively, more likely to develop first-onset MDD. None of the other sleep complaints, such as nocturnal and early morning awakening, significantly increased the risk of first-onset MDD.

The study findings were limited by several factors including the full impact of short sleep duration and lack of chronotype assessment, the researchers noted. However, “the identification of ‘difficulty initiating sleep’ as a risk factor is particularly promising because a recent meta-analysis showed that cognitive behavioural therapy, the treatment of choice for insomnia, is highly effective,” the researchers wrote. The results suggest that treating problems in sleep initiation could contribute to preventing first-onset depression and reducing the overall burden of MDD, they concluded.

The study was supported by the European Research Council. The researchers had no financial conflicts to disclose.

SOURCE: Blanken TF et al. Sleep. 2019 Dec 2. doi: 10.1093/sleep/zsz288.

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