Insomnia as a health risk factor.

This article reviewed insomnia epidemiological research, identifying areas where insomnia was a risk factor and isolating areas deserving of further investigation. Insomnia was consistently predictive of depression, anxiety disorders, other psychological disorders, alcohol abuse or dependence, drug abuse or dependence, and suicide, indicating insomnia is a risk factor for these difficulties. Additionally, insomnia was related to decreased immune functioning. The data were inconclusive regarding insomnia as a risk factor for cardiovascular disease and mortality, but sleep medication use was predictive of mortality. These results must be tempered with the knowledge that significant weaknesses existed in the studies reviewed. The main weaknesses were inadequate definition of insomnia and inadequate control for alternative explanations. Despite these limitations, this review suggests that insomnia is a risk factor for poor mental and physical health.