Previous research has identified insomnia as a predictor for the onset of depression. The aim of this meta-analysis is to investigate whether insomnia also predicts the onset of other mental disorders. Longitudinal studies were eligible for inclusion if they investigated insomnia at baseline (including nighttime-and daytime-symptoms) as a predictor of the later onset of psychopathology within a follow-up time-frame of at least 12 months. Thirteen primary studies were included. The results suggest that insomnia is a significant predictor for the onset of depression (10 studies, OR 2.83, CI 1.55-5.17), anxiety (6 studies, OR 3.23, CI 1.52-6.85), alcohol abuse (2 studies, OR 1.35, CI 1.08-1.67, and psychosis (1 study, OR 1.28, CI 1.03-1.59). The overall risk of bias in the primary studies was moderate. This meta-analysis provides evidence that insomnia increases the risk for psychopathology. A future research agenda should include more prospective studies using established diagnostic criteria, assessing insomnia at baseline and including long-term follow-up intervals evaluating a wider range of mental disorders. In addition, prospective long-term interventional studies investigating the efficacy of insomnia treatment for the prevention of mental disorders are called for.

Insomnia, the most prevalent sleep disorder worldwide, confers marked risks for both physical and mental health. Furthermore, insomnia is associated with considerable direct and indirect healthcare costs. Recent guidelines in the US and Europe unequivocally conclude that cognitive behavioural therapy for insomnia (CBT‐I) should be the first‐line treatment for the disorder. Current treatment approaches are in stark contrast to these clear recommendations, not least across Europe, where, if any treatment at all is delivered, hypnotic medication still is the dominant therapeutic modality. To address this situation, a Task Force of the European Sleep Research Society and the European Insomnia Network met in May 2018. The Task Force proposed establishing a European CBT‐I Academy that would enable a Europe‐wide system of standardized CBT‐I training and training centre accreditation. This article summarizes the deliberations of the Task Force concerning definition and ingredients of CBT‐I, preconditions for health professionals to teach CBT‐I, the way in which CBT‐I should be taught, who should be taught CBT‐I and to whom CBT‐I should be administered. Furthermore, diverse aspects of CBT‐I care and delivery were discussed and incorporated into a stepped‐care model for insomnia.

Summary Insomnia disorder comprises symptoms during night and day that strongly affect quality of life and wellbeing. Prolonged sleep latency, difficulties to maintain sleep and early morning wakening characterize sleep complaints, whereas fatigue, reduced attention, impaired cognitive functioning, irritability, anxiety and low mood are key daytime impairments. Insomnia disorder is well acknowledged in all relevant diagnostic systems: Diagnostic and Statistical Manual of the American Psychiatric Association, 5th revision, International Classification of Sleep Disorders, 3rd version, and International Classification of Diseases, 11th revision. Insomnia disorder as a chronic condition is frequent (up to 10% of the adult population, with a preponderance of females), and signifies an important and independent risk factor for physical and, especially, mental health. Insomnia disorder diagnosis primarily rests on self‐report. Objective measures like actigraphy or polysomnography are not (yet) part of the routine diagnostic canon, but play an important role in research. Disease concepts of insomnia range from cognitive‐behavioural models to (epi‐) genetics and psychoneurobiological approaches. The latter is derived from knowledge about basic sleep–wake regulation and encompass theories like rapid eye movement sleep instability/restless rapid eye movement sleep. Cognitive‐behavioural models of insomnia led to the conceptualization of cognitive‐behavioural therapy for insomnia, which is now considered as first‐line treatment for insomnia worldwide. Future research strategies will include the combination of experimental paradigms with neuroimaging and may benefit from more attention to dysfunctional overnight alleviation of distress in insomnia. With respect to therapy, cognitive‐behavioural therapy for insomnia merits widespread implementation, and digital cognitive‐behavioural therapy may assist delivery along treatment guidelines. However, given the still considerable proportion of patients responding insufficiently to cognitive‐behavioural therapy for insomnia, fundamental studies are highly necessary to better understand the brain and behavioural mechanisms underlying insomnia. Mediators and moderators of treatment response/non‐response and the associated development of tailored and novel interventions also require investigation. Recent studies suggest that treatment of insomnia may prove to add significantly as a preventive strategy to combat the global burden of mental disorders.