What are the medical causes of insomnia?

Medical Causes of Insomnia

Insomnia in adults is predominantly caused by psychiatric disorders (especially depression), chronic medical conditions, medications, and primary sleep disorders—each requiring identification and targeted treatment rather than symptomatic management alone. 1

Psychiatric Disorders

Depression is the single most important medical cause of insomnia, with patients who are depressed being 2.5 times more likely to report insomnia. 1

• Patients with psychiatric disorders have insomnia rates of 50-75%, establishing a bidirectional relationship where untreated insomnia increases risk for new onset and recurrent depression 2
• Sleep complaints may herald the onset of mood disorders or signal exacerbation of existing psychiatric conditions 2
• Anxiety disorders commonly co-occur with insomnia and perpetuate the sleep disturbance cycle 1

Chronic Medical Conditions

Cardiac and pulmonary diseases are among the most common medical contributors to insomnia, with patients reporting more sleep complaints as the number of medical conditions increases. 1

Cardiovascular and Respiratory Disorders

• Shortness of breath from chronic obstructive pulmonary disease (COPD) or congestive heart failure directly disrupts sleep 1
• Patients with respiratory symptoms are 40% more likely to report insomnia 1
• Heart disease, hypertension, and other cardiovascular conditions are independently associated with insomnia even after controlling for depression and anxiety 1

Pain-Related Conditions

• Osteoarthritis, cancer-related pain, and diabetic neuropathy cause chronic pain that prevents sleep initiation and maintenance 1
• Chronic pain conditions have insomnia rates of 50-75% 2

Neurological Disorders

• Parkinson's disease causes neurologic deficits that disrupt sleep architecture 1
• Cerebrovascular accidents (strokes) result in neurologic deficits associated with sleep complaints 1
• Cognitive decline and difficulty with balance are associated with poor sleep 1

Urological Conditions

• Nocturia from benign prostatic hyperplasia forces repeated awakenings throughout the night 1
• Urinary problems are independently associated with insomnia 1

Metabolic and Gastrointestinal Disorders

• Diabetes mellitus contributes to insomnia through multiple mechanisms including neuropathic pain 1
• Gastrointestinal problems are associated with sleep disturbances 1

Medications

Multiple medication classes directly cause or exacerbate insomnia, making medication review essential in every insomnia evaluation. 1, 2

Cardiovascular Medications

• β-blockers (e.g., propranolol) are recognized contributors to insomnia 1, 2
• α-receptor agents disrupt sleep architecture 2
• Diuretics cause nocturia leading to sleep fragmentation 1, 2

Psychiatric Medications

• SSRIs (sertraline, paroxetine) and SNRIs commonly cause or exacerbate insomnia through increased noradrenergic activation and serotonin-2 receptor stimulation 1, 2
• MAO inhibitors contribute to insomnia 2
• Atomoxetine causes sleep disruption, particularly when combined with SSRIs 2

Respiratory Medications

• Bronchodilators (albuterol) have stimulating effects that prevent sleep 1
• Theophylline disrupts sleep initiation and maintenance 1, 2

Corticosteroids and Decongestants

• Corticosteroids cause hyperarousal and sleep disruption 1
• Decongestants containing pseudoephedrine or phenylpropanolamine have stimulant effects 1

Stimulants

• Caffeine, methylphenidate, amphetamines, cocaine, and ephedrine derivatives directly cause insomnia 2
• Caffeine-containing over-the-counter medications (acetaminophen/aspirin/caffeine combinations) are often unrecognized sources 1

Narcotic Analgesics

• Oxycodone, codeine, and propoxyphene paradoxically disrupt sleep architecture despite sedating effects 2

Over-the-Counter Medications

• Cold medications containing pseudoephedrine or phenylpropanolamine cause insomnia 1
• Nicotine-containing products (gum, transdermal patches) disrupt sleep 1

Substance Use

Alcohol and nicotine are major contributors to insomnia through both direct effects and withdrawal mechanisms. 1, 2

• Alcohol use or withdrawal directly contributes to insomnia 2
• Cigarette smoking impairs sleep quality 1
• Coffee consumption, particularly after noon, disrupts sleep initiation 1, 3

Primary Sleep Disorders

True sleepiness (involuntary tendency to fall asleep) is uncommon in chronic insomnia and suggests an alternative sleep disorder requiring immediate evaluation. 2

Obstructive Sleep Apnea

• Obstructive sleep apnea commonly presents with insomnia symptoms rather than classic daytime sleepiness 1, 2
• Respiratory disturbances cause repeated arousals throughout the night 1

Movement Disorders

• Restless legs syndrome causes difficulty initiating sleep 1
• Periodic limb movement disorder causes sleep fragmentation and unrefreshing sleep 1, 2

Circadian Rhythm Disorders

• Advanced sleep phase disorder causes early morning awakenings (2-5am) with inability to return to sleep 1, 4
• Age-related changes cause the circadian clock to advance, resulting in earlier wake times 4

Critical Red Flags

Involuntary daytime sleepiness, rather than fatigue, indicates narcolepsy, sleep apnea, or periodic limb movement disorder—not primary insomnia. 2

• Fatigue (low energy, tiredness, weariness) is the expected consequence of insomnia 2
• True sleepiness (involuntary sleep episodes) requires polysomnography and specialist evaluation 2
• Mental inefficiency, severe memory impairment, or cognitive deterioration beyond typical insomnia complaints suggests alternative diagnoses 2