What causes insomnia?

What Causes Insomnia

Insomnia arises from multiple distinct etiologies that must be systematically identified, including mental disorders, medical conditions, substances/medications, poor sleep hygiene, behavioral conditioning, and primary sleep disorders—each requiring targeted evaluation and treatment rather than viewing insomnia merely as a nonspecific symptom. 1

Primary Categories of Insomnia Causes

Mental Disorders (Most Common Comorbidity)

• Psychiatric disorders cause insomnia in 50-75% of affected patients, making bidirectional evaluation essential 2
• Depression, anxiety disorders, and schizophrenia are the predominant psychiatric causes 1, 3
• Sleep complaints may herald the onset of mood disorders or signal exacerbation of existing psychiatric conditions 2
• The insomnia must be severe enough to warrant separate clinical attention beyond the "usual" sleep symptoms expected with the psychiatric disorder 1

Substances and Medications (Highly Reversible)

Stimulants that disrupt sleep include:

• Caffeine, methylphenidate, amphetamines, cocaine, and ephedrine derivatives 2
• Caffeine blocks adenosine receptors that normally promote sleep, and tolerance can develop with 400-2400 mg daily intake 4

Prescription medications commonly causing insomnia:

• Antidepressants (SSRIs, SNRIs, MAO inhibitors) 2
• Cardiovascular agents (β-blockers, α-receptor agents, diuretics) 2
• Pulmonary medications (theophylline, albuterol) 2
• Narcotic analgesics (oxycodone, codeine, propoxyphene) 2

Alcohol causes insomnia both during active use and withdrawal 2

Key clinical point: When the identified substance is stopped and discontinuation effects subside, the insomnia is expected to resolve or substantially improve 1

Medical Conditions

• Chronic pain conditions have 50-75% insomnia rates 2
• Restless legs syndrome, periodic limb movement disorder, and sleep apnea are critical to identify 3
• Any medical disorder causing nocturnal symptoms (pain, dyspnea, nocturia) can precipitate insomnia 1
• This diagnosis applies only when insomnia causes marked distress or warrants separate clinical attention beyond typical symptoms of the medical condition 1

Poor Sleep Hygiene and Behavioral Factors

Maladaptive practices that directly interfere with sleep:

• Irregular sleep scheduling 1
• Use of alcohol, caffeine, or nicotine near bedtime 1
• Engaging in non-sleep behaviors in the sleep environment (reading, watching TV in bed) 3
• Going to bed too early, late evening meals, or physical hyperactivity before bed 3

Psychophysiologic Conditioning (Perpetuating Factor)

• The bed becomes associated with waking arousal through repeated nights of "trying hard" to fall asleep, creating growing frustration and tension 1
• Excessive time spent awake in bed is particularly significant in perpetuating chronic insomnia 1
• This conditioning paradigm creates a vicious cycle where the sleep environment itself triggers arousal rather than relaxation 1

Primary Insomnia Subtypes

Idiopathic insomnia:

• Persistent complaint with insidious onset during infancy or early childhood 1
• No specific precipitating or perpetuating factors identified 1
• Few or no extended periods of sustained remission 1

Paradoxical insomnia:

• Severe or nearly "total" insomnia complaint that greatly exceeds objective evidence of sleep disturbance 1
• Reported degree of daytime deficit is not commensurate with actual sleep loss 1

Environmental and Precipitating Factors

Life Events and Stressors

• The most common precipitating factors are family, health, and work-school events, with 65% having negative emotional valence 5
• Grief, unemployment, hospitalization, or interpersonal conflicts can trigger insomnia onset 3, 5
• Social factors include divorce, separation, widowhood, low socioeconomic status, and unemployment 3

Circadian Rhythm Disruption

• Night shift work or rotating shifts produce insomnia through desynchronization 3
• Jet lag from trans-meridian flights disrupts the internal biological clock 3
• Phase delay syndrome, phase advance syndrome, or non-24-hour sleep-wake cycles 3

Critical Red Flags Indicating Alternative Diagnoses

True sleepiness (tendency to fall asleep involuntarily) is uncommon in chronic insomnia and suggests obstructive sleep apnea, narcolepsy, or periodic limb movement disorder rather than primary insomnia 2

Expected presentation: Fatigue (low energy, tiredness, weariness) is the typical daytime consequence of insomnia, not involuntary sleepiness 2

Clinical Pitfalls to Avoid

• Do not assume insomnia is merely a symptom requiring only treatment of underlying conditions—it often requires independent treatment even when comorbidities exist 1
• Polypharmacy with multiple sleep-disrupting agents (e.g., atomoxetine, SSRIs, β-blockers) creates additive or synergistic effects 2
• Caffeine metabolism slows with certain medications or liver dysfunction, independently causing insomnia 4
• Investigate both voluntary and involuntary napping patterns, as this helps distinguish insomnia from other sleep disorders 2