Sleep Disorders

Both insomnia and anxiety are common complaints, but while insomnia is a diagnostic criterion for several mental disorders, anxiety is not a criterion for primary insomnia. Numerous studies have shown a high rate of co-morbidity between anxiety disorders and insomnia. The relationship is bi-directional since insomnia contributes to the development of anxiety disorders and anxiety results in insomnia. Four relevant models of co-morbidity are discussed: one disorder represents a predisposition or vulnerability; a common cause exists for insomnia and anxiety disorders; although not casually related, the presence of one disorder influences the presentation, course or outcome of the other; and residual effects of a remitted disorder influence the presentation and the course of the other. Worry seems to be a common affective factor in both anxiety disorders and insomnia. We could not identify any naturalistic outcome and only a few treatment studies that covered both disorders. Treatment studies of post-traumatic stress disorder (PTSD), panic disorder and generalised anxiety disorder (GAD) with both anxiety and insomnia as outcome measures showed variable improvement of both pharmacotherapy and cognitive–behavioural therapy. In treatment programmes for hypnotic discontinuation, the level of anxiety was a key factor for success or not. Researchers on insomnia and anxiety disorders should have more contact, since they have much in common.