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"Sleep well and live better: overcoming insomnia using CBT" - the links between sleep disturbance and depression (2nd post)

I wrote a first post last month about a workshop I went to given by Professor Colin Espie - "Sleep well and live better: overcoming insomnia using CBT".  I mentioned that he went through the sequence: What is insomnia?  Why is it a big deal?  Why is cognitive behaviour therapy relevant?  Is it clinically effective?  How can it be delivered in real world practice?  In today's post I would like to look more at Why is it a big deal?  And I would like particularly to focus on links between insomnia and depression. 

  • Current insomnia is a major risk factor for subsequent depression, as well as for a series of other health problems.  In a recent systematic review - "Insomnia as a predictor of depression: A meta-analytic evaluation of longitudinal epidemiological studies" - Baglioni & colleagues identified and assessed 21 relevant research papers.  They concluded "Non-depressed people with insomnia have a twofold risk to develop depression, compared to people with no sleep difficulties.  Thus, early treatment programs for insomnia might reduce the risk for developing depression in the general population and be considered a helpful general preventive strategy in the area of mental health care."  Current sleep problems sadly are also associated with increased risk of developing a series of other health issues as well.  Salo et al. - "Sleep disturbances as a predictor of cause-specific work disability and delayed return to work" - followed up nearly 57,000 subjects for over 3 years and found initial sleep disturbance on most nights of the week predicted greater likelihood of subsequent extended time off work from any of a variety of problems - mental disorders, circulatory disorders, musculoskeletal symptoms, nervous system, and injuries.  This link between current insomnia and subsequent long-term disability is a strong one, so the authors of "The long-term effect of insomnia on work disability: the HUNT-2 historical cohort study" reported that "Insomnia was a strong predictor of subsequent permanent work disability ... and this association remained significant after adjustment for psychiatric and physical morbidity and for health-related behaviors."

  • Suffering from both insomnia and depression is associated with more severe depression.  In a further major recent paper assessing nearly 4,000 depressed people - "Insomnia in patients with depression: a STAR*D report" - it was found that 85% also suffered from current insomnia. Depression with sleep problems was more severe than the much less common depression without sleep problems.  Another large study - "The relationship between depression and sleep disturbances: a Japanese nationwide general population survey" - reported that "Those whose sleep duration was less than 6 hours and those whose sleep duration was 8 hours or more tended to be more depressed than those whose sleep duration was between 6 and 8 hours. Thus, sleep duration exhibited a U-shaped association with symptoms of depression.  As subjective sleep sufficiency (self-rating of sleep adequacy) decreased, symptoms of depression increased, indicating a linear inverse-proportional relationship.  Conclusion: The fact that sleep duration and subjective sleep sufficiency exhibited different relationships with symptoms of depression indicates that these 2 sleep parameters each have their own significance with regard to depression."  It's worth noting here that a diagnosis of "insomnia" involves not only criteria about time spent sleeping but also that "the sleep disturbance (or associated daytime fatigue) causes clinically significant distress or impairment in social, occupational, or other important areas of functioning".  There is interesting research suggesting that short sleep duration on its own, without linked distress or impairment, may not be much of a mental/physical health risk - see, for example "The effect of short sleep duration on coronary heart disease risk is greatest among those with sleep disturbance".  As a happy but somewhat 'short duration' sleeper myself (part of what allows me to write this blog!), I look forward to more research emerging on this latter point.

I intend to write more on insomnia and cognitive therapy soon.

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