We have thought for a number of years that chronic insomnia, as defined by an inability to fall asleep, stay asleep, or early morning awakenings, can lead to depression. On the other hand, insomnia is the most common symptom of depression. So it has always been a case of the chicken or the egg, which came first?
A very important study on our military published this month in the journal Sleep has advanced this relationship even further. It is called the Millennium Cohort Study. In it, a little over 15,000 military personal were followed from 2001 through 2008. They were screened predeployment for insomnia or short sleep duration as defined by six or less hours of sleep per night. Prior studies had shown that 20% of active duty and 40% of reserves returning from Iraq and Afghanistan have significant mental health issues. Therefore, the military wants to see if anything can be done before, not after, the fact.
In this study, they found that military personnel who had insomnia or short sleep duration before being deployed were far more likely to develop depression, anxiety, or PTSD (Post Traumatic Stress Disorder) upon returning. One theory that came out of the study is that insomnia and lack of sleep disrupts REM sleep, which is important for emotional processing, especially in the case of emotional trauma. The other theory is that these individuals tend to be ruminators and worriers to begin with thus predisposing them to stress-induced mental disorders. The jury is out on both of these theories.
So what does all of this mean? As far as our military, screening for and addressing sleep disorders before combat deployment could help to reduce mental illness in returning veterans. As for you and I, it is an important study that shows a direct link between sleep disorders such as insomnia or insufficient sleep and the development of mood and anxiety disorders such as depression, PTSD, and GAD (Generalized Anxiety Disorder). The take home message is that if you are not getting enough sleep, widely recognized to be seven to eight hours, do something about it. It looks like we finally know which is first when it comes to the chicken or the egg.
