Definition and Overview
Insomnia is a sleep disorder characterized by difficulty initiating sleep, maintaining sleep, or early morning awakening, resulting in daytime impairment despite adequate opportunity for sleep. Chronic insomnia is defined as occurring at least 3 nights per week for at least 3 months [1].
Chronic insomnia affects approximately 10% of adults, with occasional insomnia symptoms affecting up to 30-40%. It is more common in women, older adults, and those with psychiatric comorbidities [1].
Causes and Pathophysiology
Spielman's 3P model explains insomnia through Predisposing factors (genetics, temperament), Precipitating factors (stress, illness, life changes), and Perpetuating factors (maladaptive sleep behaviors, dysfunctional beliefs about sleep) [2].
Hyperarousal is the central mechanism. Insomnia patients show elevated cortisol, increased metabolic rate, heightened sympathetic activity, and reduced heart rate variability (HRV), even during sleep. This reflects autonomic nervous system imbalance with sympathetic predominance [3].
Neurotransmitter imbalances include reduced GABA (inhibitory) and increased orexin (wake-promoting) signaling. The ascending reticular activating system remains overactive.
Symptoms
- Difficulty falling asleep (sleep onset insomnia): lying awake for >30 minutes
- Difficulty staying asleep (sleep maintenance insomnia): multiple awakenings
- Early morning awakening: waking >30 minutes before desired time
- Daytime consequences: fatigue, poor concentration, mood disturbance, impaired performance
Associated symptoms include anxiety about sleep, autonomic symptoms (palpitations, muscle tension), and increased caffeine/alcohol use as compensatory behaviors.
Diagnosis
Clinical diagnosis based on patient history using ICSD-3 criteria. The Insomnia Severity Index (ISI) quantifies severity. A 2-week sleep diary documents sleep patterns [1].
Polysomnography is not routinely needed but indicated when sleep apnea or periodic limb movements are suspected. Actigraphy provides objective sleep-wake data over 1-2 weeks.
Treatment
CBT for Insomnia (CBT-I)
CBT-I is the gold-standard first-line treatment, superior to medication for long-term outcomes [4]. Components include:
- Sleep restriction: limiting time in bed to match actual sleep time
- Stimulus control: bed only for sleep and sex; leave bed if awake >20 minutes
- Cognitive restructuring: addressing catastrophic thoughts about sleep
- Sleep hygiene education
- Relaxation training: progressive muscle relaxation, deep breathing
Pharmacotherapy
Melatonin receptor agonists (ramelteon) and orexin receptor antagonists (suvorexant, lemborexant) are preferred for their favorable side effect profile. Z-drugs (zolpidem, eszopiclone) are effective short-term but carry risks of dependence and complex sleep behaviors [5].
Low-dose trazodone and doxepin are sedating antidepressants used off-label for insomnia.
Lifestyle Management
- Consistent sleep/wake schedule (including weekends)
- Cool, dark, quiet bedroom environment
- No screens 1 hour before bed
- No caffeine after noon; limit alcohol
- Regular exercise (but not within 3 hours of bedtime)
- Relaxation routine before bed