Anxiety disorders occur due to dysfunction in the regulation of fear, worry and anxiousness, and are reported to have a worldwide prevalence of approximately 30%. Sleep disturbances are commonly observed in patients with anxiety disorder, and 50-90% of individuals with anxiety disorders report some insomnia-related symptoms. Fear and anxiety are crucial causal and protracting factors for chronic insomnia. Therefore, patients with anxiety disorders may be vulnerable to insomnia. Benzodiazepines, which have been used as anxiolytics, are also effective for the treatment of insomnia symptoms. This demonstrates the pathological commonality between anxiety and insomnia disorders.
 Insomnia disorders may be regarded as "anxiety disorders", wherein the patient's anxiety manifests as only insomnia or as mental and physical problems regarded as expected consequences of insomnia. Indeed, most of the daytime dysfunction in insomniacs include anxiety or hypochondriac sequelae. It is therefore assumed that there are many potential comorbid conditions with insomnia and anxiety disorders as symptoms. Recent international clinical practice guidelines recommend the use of SSRIs/SNRIs and cognitive behavioral therapy instead of benzodiazepine anxiolytics for the treatment of anxiety disorders. However, insomnia concurrent with anxiety disorders should be treated while considering anxiety-insomnia pathology to the greatest extent possible. Treatment of insomnia as a condition distinct from anxiety disorders carries a significant risk of over-prescription, which may in turn lead to anxiety-insomnia complications.
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