Insomnia

Insomnia is the most common sleep complaint in the general population. The condition can manifest itself in several ways and can be triggered in different scenarios, facts that render it a peculiar and multifaceted clinical entity. Nosologically, insomnia can be understood as a symptom or as a disorder with its own characteristics and has a chronic course. Insomnia disorder is more common among women and older adults, as well as in social risk strata, and is usually associated with comorbidities, particularly mental disorders. The diagnostic criteria for insomnia disorder have changed as new perspectives emerge. The cause-based classification (e.g., secondary to clinical diseases; associated with poor sleep hygiene) was abandoned in the latest editions of clinical manuals, which combined the subdivisions into a single entity, insomnia disorder. There are varied pathophysiological mechanisms that involve physiological and psychological features. The chronification of insomnia is more easily understood based on psychosocial models, especially Spielman’s model that explains the development and maintenance of insomnia based on predisposing, precipitating, and perpetuating factors. The most recent challenge is to determine new clinical phenotypes that allow a more assertive approach and treatment.