Insomnia
Diagnosis and the 3P model
Chronic insomnia disorder is defined by difficulty initiating or maintaining sleep, or early-morning awakening, occurring ≥3 nights/week for ≥3 months, with daytime consequences despite adequate opportunity to sleep. It is a clinical diagnosis; polysomnography is not routinely required unless another disorder (e.g., OSA, periodic limb movements) is suspected.
The 3P model (predisposing, precipitating, perpetuating) explains chronification. Key perpetuating factors are conditioned arousal, irregular sleep schedules, and maladaptive behaviors (extended time in bed, daytime napping, clock-watching). The hyperarousal concept-physiologic and cognitive-distinguishes insomnia from simply insufficient sleep opportunity.
Treatment hierarchy
CBT-I is first-line for chronic insomnia in adults and includes stimulus control, sleep restriction, relaxation training, cognitive restructuring, and sleep hygiene. Hypnotics are adjunctive and carry risks: benzodiazepines and Z-drugs (tolerance, falls, complex sleep behaviors), and sedating antidepressants (e.g., low-dose doxepin, trazodone) are used off-label or on-label depending on the agent. Orexin receptor antagonists target the wake-promoting system.
Traps: recommending sleep hygiene alone as adequate therapy; confusing sleep restriction (compressing time in bed to match actual sleep time) with sleep deprivation; and labeling early-morning awakening as insomnia when it is a depression or circadian feature. Also do not diagnose insomnia when the patient simply has insufficient sleep opportunity-that is insufficient sleep syndrome.
Rule of thumb: Stimulus control = bed for sleep and sex only, leave the bed if awake >~20 minutes, return when sleepy.
Worked example: A patient in bed 9 hours but sleeping 6 has a sleep efficiency of ~67%; sleep restriction would initially set time in bed near 6 hours, then titrate upward as efficiency exceeds ~85–90%.