[Insomnia--state of the science]

Diagnostic systems such as the international classification of diseases (ICD-10) or the diagnostic and statistical manual of mental disorders (DSM IV) have frequently been criticized as not adequately reflecting the complexity and heterogeneity of insomnia. Progress was made through the introduction of the international classification of sleep disorders (ICSD-2) and the research diagnostic criteria (RDC). The DSM-5 introduced the new category of insomnia disorder, thus relinquishing the traditional dichotomy of primary versus secondary insomnia. Recent basic research indicates that genetic and epigenetic factors are involved in the etiology of insomnia; the so-called three P model (i.e. predisposing, precipitating and perpetuating factors) and the hyperarousal concept have gained much attention in trying to explain the pathophysiology of insomnia. With respect to the cognitive-behavioral therapy of insomnia (CBT-I), a plethora of empirical evidence supports the first-line character of this type of treatment for insomnia. Unfortunately, CBT-I is still administered to only a minority of afflicted patients, probably due to a lack of resources in the healthcare system. As a consequence, stepped-care models to improve insomnia therapy encompass self-help programs, internet-based treatment avenues, community-centered activities (specially trained nurses) and as a last resort medical specialists/psychotherapists and sleep experts to deal with insomnia.