The study, published in the journal SLEEP, was carried out by researchers at the Perelman School of Medicine at the University of Pennsylvania and the Naval Health Research Center.
Pre-existing symptoms of insomnia appear to increase the risk of developing mental disorders after deployment.
Lead study author of the study, Philip Gehrman, PhD, assistant professor of Psychology in the Department of Psychiatry, member of the Penn Sleep Center, and the Philadelphia VA Medical Center, said: "Understanding environmental and behavioral risk factors associated with the onset of common major mental disorders is of great importance in a military occupational setting."
"This study is the first prospective investigation of the relationship between sleep disturbance and development of newly identified positive screens for mental disorders in a large military cohort who have been deployed in support of the recent operations in Iraq or Afghanistan."
The research team used self-reported data from the Millennium Cohort Study and assessed the link between symptoms of insomnia before military deployment and the development of mental disorders once they return back home.
Through multivariable logistic regression, the team analyzed the risk of PTSD, depression, and anxiety and adjusted the results to account for factors such as combat-related trauma.
A total of 15,204 service members were analyzed, at the end of deployment 522 of them developed PTSD, 303 suffered from depression, and 151 experienced severe anxiety.
Pre-deployment insomnia symptoms substantially increased the risk of developing mental disorders following military deployment.
Gehrman said that the most interesting aspect of the findings of this study is "not only the degree of risk conferred by pre-deployment insomnia symptoms, but also the relative magnitude of this risk compared with combat-related trauma.The risk conferred by insomnia symptoms was almost as strong as our measure of combat exposure in adjusted models."
Even those who slept fewer than six hours each night (not general insomnia) were at an increased risk of PTSD.
"We found that insomnia is both a symptom and a risk factor for mental illness and may present a modifiable target for intervention among military personnel.
We hope that by early identification of those most vulnerable, the potential exists for the designing and testing of preventive strategies that may reduce the occurrence of PTSD, anxiety, and depression."
The researchers stressed the need for additional studies to be carried out in order to evaluate the full impact that sleep has on the mental health of military personnel, as well as to develop means of intervention that could help them.
A previous study, published in the journal Archives of General Psychiatry, found that military service members who screened positive for mental health disorders before deployment were at a much higher risk of developing post-deployment post-traumatic stress disorder (PTSD) symptoms than their colleagues without these risk factors.
In addition researchers have identified a high prevalence of sleep disorders and a very high rate of short sleep duration among active duty military personnel. Vincent Mysliwiec, MD, at Madigan Army Medical Center in Tacoma, Washington, said that "while sleep deprivation is part of the military culture, the high prevalence of short sleep duration in military personnel with sleep disorders was surprising."
Written by Joseph Nordqvist