Chronic Insomnia: Causes, Diagnosis, and Evidence-Based Treatment

What Exactly Is Chronic Insomnia?

Chronic insomnia is a sleep disorder defined by persistent difficulty initiating sleep, maintaining sleep, or waking too early, combined with daytime impairment, occurring at least three nights per week for at least three months. The International Classification of Sleep Disorders, Third Edition (ICSD-3) requires that symptoms occur despite adequate opportunity and circumstances for sleep, distinguishing the disorder from voluntary sleep restriction. Prevalence estimates from population-based studies cluster between 10 and 15 percent of adults, with women affected approximately 1.4 times more often than men. [1]

Daytime consequences are the feature that makes chronic insomnia a medical condition rather than a preference. Fatigue, attention deficits, mood disturbance, and reduced work performance all qualify as impairment under ICSD-3. A 2011 meta-analysis in Sleep (N=91,832 pooled across 21 studies) found that chronic insomnia was associated with a 2.1-fold increased risk of developing a depressive disorder within one year. [2] That bidirectional relationship between insomnia and psychiatric illness is one reason clinicians should never dismiss sleep complaints as secondary.

Acute Insomnia vs. Chronic Insomnia

Acute insomnia lasts fewer than three months and is almost always linked to an identifiable stressor, such as a new job, bereavement, or illness. It affects up to 30 to 35 percent of adults in any given year. [3] Most acute cases resolve on their own within weeks once the precipitating stressor passes. The risk of chronification is real, however. Research from the Epidemiology of Sleep Disorders Study suggests that roughly 40 percent of patients with acute insomnia go on to develop chronic insomnia if the acute episode is not addressed early. [4] Brief behavioral interventions during the acute phase may reduce that transition rate.

How Chronic Insomnia Is Diagnosed

Diagnosis depends on clinical history and a prospective sleep diary, not a polysomnography (PSG). The American Academy of Sleep Medicine (AASM) practice parameters state explicitly that PSG is not indicated for the routine evaluation of chronic insomnia. [5] A two-week sleep diary captures sleep onset latency (SOL), wake after sleep onset (WASO), total sleep time (TST), and sleep efficiency (SE), all of which guide treatment decisions without the cost and inconvenience of a lab study.

Clinicians should also screen for comorbid conditions at intake. The STOP-BANG questionnaire takes under two minutes to administer and has a sensitivity of 93.4 percent for moderate-to-severe obstructive sleep apnea. [6] The International RLS Study Group Rating Scale quantifies restless legs severity in about five minutes. Actigraphy across seven to fourteen days adds objective data when the history is unclear, though insurance coverage varies.

Key validated instruments include:

• Insomnia Severity Index (ISI): a 7-item self-report tool; scores of 15 or higher indicate moderately severe insomnia
• Pittsburgh Sleep Quality Index (PSQI): captures sleep quality across a one-month window
• Epworth Sleepiness Scale (ESS): high scores (above 10) suggest a hypersomnolence component that warrants PSG

A score of 15 or higher on the ISI in a patient who has experienced symptoms for more than 12 weeks, with no identifiable primary sleep disorder, is sufficient clinical grounds to initiate CBT-I.

CBT-I: The First-Line Treatment Every Patient Should Receive

CBT-I outperforms sleep medication for long-term outcomes in every head-to-head randomized controlled trial conducted to date. A 2015 meta-analysis in Annals of Internal Medicine covering 20 trials found that CBT-I reduced SOL by a mean of 19.1 minutes and WASO by 26.0 minutes versus control, with benefits maintained at six-to-twelve-month follow-up, unlike benzodiazepine receptor agonists whose efficacy wanes with tolerance. [7] The American College of Physicians Clinical Practice Guideline (2016) gives CBT-I a strong recommendation, moderate-quality evidence for all adult patients with chronic insomnia disorder, stating: "ACP recommends that all adult patients receive CBT-I as the initial treatment for chronic insomnia disorder." [8]

The core components of CBT-I are:

1. Sleep restriction therapy (SRT). The clinician prescribes a time-in-bed window matched to the patient's actual sleep time, typically 5.5 to 6 hours initially, then titrated upward by 15 to 30 minutes per week as sleep efficiency exceeds 85 percent.
2. Stimulus control. The bed is reserved for sleep and sex only. Patients leave the bed if unable to sleep within approximately 20 minutes, returning only when sleepy.
3. Cognitive restructuring. Dysfunctional beliefs such as "I must get eight hours or tomorrow is ruined" are identified and tested with behavioral experiments.
4. Sleep hygiene education. Covers caffeine cutoffs (ideally before noon for sensitive individuals), alcohol timing, light exposure, and bedroom temperature (65 to 68 degrees Fahrenheit is optimal for most adults).
5. Relaxation techniques. Progressive muscle relaxation or diaphragmatic breathing lowers pre-sleep arousal.

A standard course runs six to eight weekly sessions. Digital CBT-I programs such as Somryst (FDA-cleared) achieve comparable short-term outcomes to therapist-delivered CBT-I for patients without immediate access to a behavioral sleep medicine specialist. A 2019 RCT in JAMA Internal Medicine (N=303) found Somryst reduced ISI scores by 8.9 points versus 3.1 for sleep hygiene education alone (P<0.001). [9]

The table below outlines the HealthRX Sleep Medicine team's triage framework for matching treatment intensity to insomnia severity at first visit:

| ISI Score | STOP-BANG Score | Recommended First Step | |---|---|---| | 8-14 (subthreshold) | <3 | Sleep hygiene + digital CBT-I | | 15-21 (moderate) | <3 | Therapist-delivered CBT-I; consider short-term pharmacotherapy if occupational impairment is severe | | 22-28 (severe) | <3 | Immediate CBT-I referral + pharmacotherapy bridge | | Any | 3 or higher | PSG to exclude OSA before initiating CBT-I or hypnotics |

Pharmacotherapy for Chronic Insomnia

Medication is appropriate as a short-term bridge to CBT-I or when CBT-I has produced incomplete response. No hypnotic is approved for indefinite use. The AASM 2017 clinical practice guideline for pharmacologic treatment of chronic insomnia in adults provides the following drug-specific recommendations. [10]

Doxepin 3 to 6 mg received a strong recommendation for sleep maintenance insomnia. At these low doses, doxepin acts exclusively as an H1 antihistamine, carrying minimal anticholinergic burden and no abuse potential, making it a reasonable option for older adults.

Suvorexant (Belsomra) 10 to 20 mg and lemborexant (Dayvigo) 5 to 10 mg are dual orexin receptor antagonists (DORAs). Both received strong AASM recommendations. In the SUNRISE-2 trial (N=949), lemborexant 10 mg reduced subjective SOL by 19.7 minutes versus placebo at month one (P<0.001) and maintained efficacy at six months without evidence of tolerance. [11]

Eszopiclone (Lunesta) 1 to 3 mg received a weak AASM recommendation. The ESTEEM trial showed sustained efficacy over six months, but next-day sedation and a bitter taste are common complaints.

Zolpidem (immediate release 5 to 10 mg, extended release 6.25 to 12.5 mg) carries an FDA-required warning about complex sleep behaviors including sleep-driving. The FDA reduced recommended doses in 2013 for women (from 10 mg to 5 mg immediate release) after pharmacokinetic data showed women eliminate the drug more slowly. [12]

Benzodiazepines such as temazepam carry Schedule IV designation and a meaningful risk of dependence with nightly use beyond four weeks. They are not preferred by current guidelines for chronic insomnia management.

Drugs to avoid. Over-the-counter diphenhydramine (Benadryl, ZzzQuil) is not recommended. It loses efficacy within two to three nights due to rapid tolerance, carries anticholinergic burden, and a 2019 JAMA Internal Medicine study linked cumulative diphenhydramine exposure to increased dementia risk. [13]

Obstructive Sleep Apnea and Its Overlap With Insomnia

Obstructive sleep apnea (OSA) and chronic insomnia coexist in an estimated 39 to 58 percent of patients referred to sleep clinics, a phenotype called COMISA (comorbid insomnia and sleep apnea). [14] OSA occurs when the upper airway collapses repeatedly during sleep, causing oxygen desaturations and cortical arousals. Each arousal fragments sleep architecture in a way the patient often experiences as insomnia rather than breathing difficulty.

The AASM defines OSA severity by the apnea-hypopnea index (AHI): mild is 5 to 14 events per hour, moderate 15 to 29, and severe 30 or more. Untreated moderate-to-severe OSA carries a 2.5-fold increased risk of incident hypertension and a roughly 3-fold increased risk of cardiovascular events compared with matched controls without OSA, according to data from the Sleep Heart Health Study (N=6,132). [15]

CPAP therapy at 4 to 20 cm H2O is the standard treatment for moderate-to-severe OSA. In COMISA patients, starting CPAP without addressing the insomnia first results in poor CPAP adherence (mean nightly use below 4 hours in multiple studies). The preferred sequence is to treat insomnia with CBT-I first or concurrently, then introduce CPAP. A 2019 RCT in Sleep (N=145) found that CBT-I delivered before CPAP initiation improved CPAP adherence by 63 minutes per night at three months compared with CPAP alone. [16]

Mandibular advancement devices are an alternative for mild-to-moderate OSA in patients who cannot tolerate CPAP. Upper airway stimulation (Inspire therapy) is FDA-approved for moderate-to-severe OSA in patients with AHI between 15 and 65 who have failed CPAP.

Restless Legs Syndrome and Periodic Limb Movement Disorder

Restless legs syndrome (RLS), also called Willis-Ekbom disease, is a sensorimotor disorder defined by an irresistible urge to move the legs, typically accompanied by uncomfortable sensations described as crawling, pulling, or burning. Symptoms appear or worsen at rest, are worst in the evening or night, and are temporarily relieved by movement. These four diagnostic criteria, established by the International RLS Study Group, must all be present for a diagnosis. [17]

RLS affects 5 to 15 percent of the general population and is twice as common in women. [18] Secondary causes include iron deficiency (ferritin below 50 mcg/L worsens symptoms even without frank anemia), end-stage renal disease, pregnancy, and dopamine-antagonist medications including metoclopramide and most antipsychotics.

First-line pharmacotherapy for moderate-to-severe RLS includes the alpha-2-delta ligands gabapentin enacarbil (Horizant) 600 mg daily and pregabalin 150 to 300 mg at bedtime, both of which received Level A evidence in the AASM practice parameter. [19] Dopamine agonists pramipexole and ropinirole were historically first-line but are now deprioritized due to augmentation, a paradoxical worsening of symptoms with long-term use that affects up to 50 percent of patients on pramipexole within five years of treatment.

Iron supplementation targeting ferritin above 75 mcg/L resolves RLS in a meaningful proportion of patients. A 2019 trial in Sleep Medicine (N=64) found that intravenous ferric carboxymaltose produced at least a 3-point reduction in IRLS score in 58 percent of patients with ferritin below 100 mcg/L at four weeks. [20]

Periodic limb movement disorder (PLMD) is diagnosed by PSG and defined as more than 15 limb movements per hour of sleep in adults, each causing a brief EEG arousal. PLMD often coexists with RLS but can occur independently. Patients typically report insomnia or unrefreshing sleep without recognizing that they move in the night. Treatment mirrors RLS pharmacotherapy. Bed partners are frequently the first to notice the repetitive kicks.

Special Populations: Insomnia in Perimenopause and Older Adults

Insomnia prevalence doubles during the menopause transition. Declining estradiol disrupts thermoregulation, causing vasomotor symptoms (hot flashes, night sweats) that fragment sleep architecture. Among women in the Study of Women's Health Across the Nation (SWAN, N=3,302), night sweats were independently associated with a 3.4-fold increase in self-reported sleep disturbance. [21] For perimenopausal women whose insomnia is primarily driven by vasomotor symptoms, menopausal hormone therapy (MHT) can reduce nocturnal awakenings, though CBT-I remains the foundation.

In adults over 65, sedating hypnotics carry heightened risk. The American Geriatrics Society Beers Criteria lists all benzodiazepines and non-benzodiazepine receptor agonists (z-drugs) as potentially inappropriate medications in older adults due to increased risk of falls, fractures, and cognitive impairment. [22] Low-dose doxepin (3 to 6 mg) and the DORAs are preferred in this age group when pharmacotherapy is truly necessary after a full CBT-I course.

When to Refer to a Sleep Specialist

Primary care management is appropriate for uncomplicated chronic insomnia with no features suggesting a primary sleep disorder. Refer to a board-certified sleep medicine physician when:

• STOP-BANG score is 3 or higher, or the bed partner reports witnessed apneas
• RLS symptoms are refractory after first-line treatment
• PSG is needed to rule out PLMD or parasomnias
• CBT-I has been completed (six to eight sessions) with less than 50 percent improvement in ISI score
• Suspected narcolepsy or circadian rhythm disorder (DSWPD, non-24-hour sleep-wake disorder)
• Sleep-related eating disorder or REM sleep behavior disorder is suspected

A referral delay of more than three months is associated with progression of insomnia severity and increased likelihood of secondary depression based on prospective registry data. Prompt referral protects the patient and reduces downstream healthcare utilization.

Lifestyle and Behavioral Factors That Drive Chronic Insomnia

Sleep hygiene is necessary but not sufficient on its own. Patients who receive sleep hygiene education alone show only marginal ISI reductions (mean 1 to 2 points) in controlled trials, far below the 8-point threshold considered clinically meaningful. [9] What matters more is the patient's conditioned arousal response to the bed and bedroom.

Caffeine has a half-life of 5 to 7 hours. A 200 mg dose consumed at 3:00 PM leaves 100 mg circulating at 8:00 to 10:00 PM in average metabolizers. CYP1A2 slow metabolizers retain caffeine even longer. Alcohol reduces SOL briefly but increases WASO in the second half of the night by suppressing REM sleep and causing rebound sympathetic activation.

Exercise shortens SOL and increases slow-wave sleep, with a dose-response that favors moderate-intensity aerobic activity (150 minutes per week per CDC physical activity guidelines). [23] Vigorous exercise within 2 hours of bedtime does not universally worsen sleep; individual variation is high, and patients should not avoid evening exercise if it is their only practical option.

Screen light before bed deserves nuance. Blue-wavelength light from screens suppresses melatonin by roughly 1.5 hours at 200 lux exposure over 90 minutes. Blue-light filtering glasses attenuate this effect but do not eliminate it. Dimming all room light to below 10 lux in the 60 minutes before bed is more effective than glasses alone.