Definition and Diagnosis
Insomnia disorder is characterized by persistent difficulty with sleep initiation, maintenance, or early-morning awakening, occurring at least three nights per week for three months or more, despite adequate opportunity for sleep, and resulting in significant daytime impairment.
Epidemiology
Insomnia is one of the most common sleep complaints, with acute insomnia affecting up to a third of adults at some point and chronic insomnia disorder affecting an estimated 6-10% of the general population, more common in women and older adults.
Risk Factors
Risk factors include stress, anxiety and mood disorders, poor sleep habits, shift work, chronic pain or medical illness, caffeine or stimulant use, and a predisposition toward heightened physiological or cognitive arousal.
Symptoms and Subtypes
Symptoms include difficulty falling asleep, frequent nighttime awakenings, early morning awakening with inability to return to sleep, and consequent daytime fatigue, mood disturbance, and impaired concentration or performance.
Diagnosis
Diagnosis is largely clinical, based on sleep history (often supported by a sleep diary), and DSM-5-TR criteria requiring symptoms at least three nights a week for three months with associated distress or impairment, after ruling out other primary sleep, medical, or psychiatric causes.
Treatment
Cognitive behavioral therapy for insomnia (CBT-I) is first-line and more effective long-term than medication, incorporating sleep restriction, stimulus control, and cognitive techniques. Short-term pharmacotherapy (e.g., certain hypnotics) may be used adjunctively in select cases.
Prognosis
With CBT-I, most individuals experience significant and durable improvement in sleep; untreated chronic insomnia is associated with increased risk of mood disorders, cardiovascular disease, and impaired quality of life.
Reference
New Oxford Textbook of Psychiatry (2nd ed.).