Insomnia: Why It Persists, How It's Diagnosed, and the Treatment That Works Best

Insomnia is difficulty falling asleep, staying asleep, or waking too early despite adequate opportunity to sleep, together with a daytime consequence — fatigue, poor concentration, irritability, or low mood. When it occurs at least three nights a week for three months or longer, it is chronic insomnia disorder, which is a diagnosis in its own right rather than a symptom of something else.

The counterintuitive part is the physiology. People with chronic insomnia are not less sleepy than good sleepers; on objective testing they are often less able to fall asleep during the day, not more. What they have is elevated arousal — cognitive, physiological, and cortical — that persists into the night. Insomnia is a disorder of being too awake, not of needing more sleep.

This page is educational, not medical advice.

Why insomnia persists after the trigger is gone

Most chronic insomnia starts with something identifiable: a stressful stretch at work, a bereavement, a newborn, an illness, a course of steroids, a schedule change. That is the precipitating event. What makes it chronic is what happens next.

Two perpetuating factors do most of the damage. The first is spending more time in bed to compensate — going to bed earlier, lying in later, napping. That dilutes sleep drive across a longer window and produces more wakefulness in bed, not less sleep debt. The second is conditioned arousal: after enough nights of lying awake, the bed itself becomes a cue for alertness and for the anxious monitoring of whether sleep is coming. At that point the original trigger is irrelevant. The insomnia maintains itself.

This is also why clock-watching and effortful trying make things worse, and why the 3 a.m. awakening feels so distinctive. We unpacked the mechanisms behind that specific pattern in why you wake at 3 AM.

What else can look like insomnia

A significant share of patients treated for insomnia have an untreated breathing problem underneath it. Sleep-disordered breathing fragments sleep and produces repeated awakenings that the patient experiences as insomnia — particularly the sleep-maintenance kind. The overlap has a name, COMISA (comorbid insomnia and sleep apnea), and it is common enough that persistent middle-of-the-night awakening deserves screening: see can't stay asleep? your breathing might be waking you up. If snoring, witnessed pauses, morning headache, or daytime sleepiness are present, evaluate for obstructive sleep apnea before or alongside insomnia treatment.

Other mimics worth excluding: restless legs syndrome, where the problem is an urge to move rather than an inability to sleep; circadian rhythm disorders, where sleep is normal but mistimed, common in shift workers and delayed sleep phase; anxiety and depressive disorders, which both cause and are worsened by insomnia; chronic pain; and medications including stimulants, some antidepressants, decongestants, beta-agonists, and steroids. Perimenopause is a frequent inflection point, driven by vasomotor symptoms and hormonal change — covered in perimenopause as a sleep and metabolic turning point.

How insomnia is diagnosed

Insomnia is a clinical diagnosis. It is made from a careful history — sleep timing, time in bed versus time asleep, what happens during awakenings, daytime consequences, substances, medications, mood, and pain — usually supported by a one- to two-week sleep diary that reveals patterns patients cannot recall accurately from memory.

A sleep study is not required to diagnose insomnia and should not be ordered routinely. It is indicated when the history suggests sleep apnea, periodic limb movements, or another sleep disorder, or when a patient has not responded to appropriate treatment. Wearables can be useful for tracking timing and regularity, but their sleep-staging estimates are not diagnostic, and in anxious sleepers, obsessive data-checking can itself worsen the problem.

Treatment: CBT-I first, and why

Cognitive behavioral therapy for insomnia is the recommended first-line treatment for chronic insomnia in adults across major clinical guidelines — ahead of medication, not as an alternative to it. It typically runs four to eight sessions and works by dismantling the perpetuating factors directly rather than sedating through them.

Its components: sleep restriction, which compresses time in bed to match actual sleep and rebuilds sleep pressure; stimulus control, which re-links the bed with sleep by getting out of bed when awake; cognitive work on catastrophic beliefs about sleep loss; relaxation and de-arousal techniques; and consistent wake timing and light exposure to anchor the circadian rhythm. Effects are comparable to sleep medication in the short term and, unlike medication, they hold after treatment ends. Our full program overview is at CBT-I.

Medication has a role — for short-term use during an acute stressor, or when CBT-I is unavailable or has not worked — but it is adjunctive. Different agents carry different risks around next-day impairment, tolerance, dependence, falls in older adults, and rebound insomnia on discontinuation, and over-the-counter antihistamine sleep aids are a poor long-term choice. We walk through each class, including melatonin and what the dosing evidence actually supports, in our sleep aids and medications guide. Any decision about starting, changing, or stopping a sleep medication belongs with your prescribing clinician.

Frequently asked questions