Why You Can't Sleep — 8 Medical Reasons and What Actually Helps
Why You Can't Sleep: 8 Medical Reasons and What Actually Helps
Chronic insomnia is usually not just stress. Most cases have a specific, treatable cause.
Sleep problems are described vaguely and treated vaguely. "I don't sleep well" could mean difficulty falling asleep, waking repeatedly, waking too early, sleeping too much, sleeping enough but feeling unrefreshed, or genuinely poor quality sleep at every stage. Each of these has different causes.
This isn't about sleep hygiene tips you already know. It's about the medical reasons sleep fails, the specific ones that go undiagnosed for years.
8 Medical Reasons Sleep Breaks Down
Your airway collapses partially or fully during sleep. Your brain detects the drop in oxygen and briefly wakes you to restore breathing. You might do this dozens of times per hour without full consciousness. You wake feeling like you haven't slept. Your partner notices the snoring and gasping.
OSA affects around 10 to 30% of adults and is significantly underdiagnosed, particularly in women, where the presentation is often atypical (fatigue and insomnia rather than snoring). Diagnosed with an overnight sleep study (polysomnography or home sleep test). Treated with CPAP, mandibular advancement device, or weight loss in appropriate patients. CPAP has strong evidence for improving daytime sleepiness, blood pressure, and cognitive function.
Iron deficiency is one of the most underrecognised causes of both insomnia and restless legs syndrome (RLS). Iron is a cofactor for dopamine synthesis in the brain. Low iron disrupts dopamine signalling in the substantia nigra, which contributes to the uncomfortable leg sensations of RLS that prevent sleep.
Critically: your haemoglobin can be normal while ferritin (stored iron) is depleted. Always check ferritin if sleep problems are present, not just full blood count. A ferritin below 50 micrograms/L in someone with RLS or insomnia is worth treating.
Anxiety creates hyperarousal: the nervous system is running at higher baseline activation. Cortisol and noradrenaline levels stay elevated into the evening. This directly delays sleep onset because sleep requires a drop in core body temperature and a shift from sympathetic to parasympathetic dominance.
Cognitive arousal (the racing, looping thoughts at midnight) is often the most debilitating part. CBT-I (see below) specifically targets this through stimulus control and cognitive restructuring techniques.
Hyperthyroidism causes insomnia, night sweats, racing heart, and anxiety, all of which shred sleep quality. Even subclinical hyperthyroidism (suppressed TSH with normal T4) can cause significant sleep disruption. Hypothyroidism, on the other hand, is associated with excessive daytime sleepiness and in some cases, worsens sleep apnoea.
A TSH test is cheap and should be on the differential for any unexplained sleep disorder, particularly with associated weight change, heat or cold intolerance, or heart palpitations.
Delayed sleep phase syndrome (DSPS) is a legitimate circadian disorder, not just being a "night owl." The person's sleep-wake cycle is shifted 2 or more hours later than socially conventional. They can't fall asleep until 2am. They sleep until 10am if undisturbed. Their sleep quality is normal; the timing is wrong.
Light therapy (10,000 lux bright light exposure within 30 minutes of waking) and chronotherapy are first-line treatments. Low-dose melatonin (0.5 to 1mg) taken 5 to 6 hours before the desired sleep time (not at bedtime) can shift the circadian phase.
RLS causes an irresistible urge to move the legs, accompanied by uncomfortable sensations (crawling, pulling, aching) that are worse at rest and in the evening, and temporarily relieved by movement. This is a neurological disorder, not a habit or anxiety. Around 5 to 10% of the adult population has it.
Primary causes: iron deficiency, dopamine pathway dysfunction, genetics. Secondary causes: pregnancy, kidney disease, certain medications (SSRIs, antihistamines, antipsychotics). Iron replenishment helps many. Dopamine agonists (pramipexole, ropinirole) are second-line but carry augmentation risk with long-term use.
Depression profoundly disrupts sleep architecture. Early morning awakening (waking at 3 to 4am unable to return to sleep) is a classic feature of depression, particularly melancholic subtype. Depression also reduces slow-wave (deep) sleep and increases REM sleep, changing the qualitative experience of sleep even when duration seems adequate.
Sleep disturbance is both a symptom and a perpetuating factor: poor sleep worsens depression, which worsens sleep. Treating the depression usually improves sleep, though some antidepressants (SSRIs, SNRIs) can initially worsen sleep onset. Mirtazapine and trazodone have sedating properties that can be useful in depression with insomnia.
Pain and sleep have a bidirectional relationship. Pain disrupts sleep, and sleep deprivation lowers the pain threshold (the amount of stimulus needed to cause pain). People with fibromyalgia, arthritis, back pain, or headache disorders almost universally report poor sleep, and improving sleep quality is part of pain management.
The mechanism: pain activates the ascending arousal system, preventing deep sleep stages. NSAIDs before bed help some patients. Amitriptyline (at low doses, 10 to 25mg) has evidence for both pain and sleep, particularly in fibromyalgia and chronic headache.
What Actually Treats Chronic Insomnia
CBT-I is the first-line treatment for chronic insomnia, with stronger long-term evidence than sleep medications. NICE guidelines recommend it before pharmacotherapy. It has 5 components:
Medications: What the Evidence Says
| Medication | Mechanism | Evidence | Concerns |
|---|---|---|---|
| Melatonin (0.5 to 3mg) | Circadian signal | Good for circadian disorders, jet lag. Modest for sleep-onset insomnia. | Generally safe. Low abuse potential. |
| Z-drugs (zopiclone, zolpidem) | GABA-A agonist | Effective short-term. Reduces sleep onset by ~15 minutes. | Dependence risk. Next-day sedation. Not for long-term use. |
| Antihistamines (diphenhydramine) | Histamine block | Modest short-term effect. Rapid tolerance develops. | Anticholinergic effects. Not recommended for over-60s. |
| Mirtazapine (low dose) | H1 + alpha-2 antagonist | Improves sleep architecture. Useful in depression + insomnia. | Weight gain, sedation (which is the point at low doses). |
| Suvorexant (orexin antagonist) | Blocks wake signal | RCT evidence for sleep onset and maintenance. Newer class. | Expensive. Next-day sedation in some. Not widely available. |
Sleep medications treat the symptom. CBT-I treats the cause. The ideal approach identifies why sleep is broken and addresses that, rather than sedating the problem.
The Bottom Line
If you've had sleep problems for more than 3 months and sleep hygiene advice hasn't helped, you need a proper evaluation. Ask your doctor to check ferritin, TSH, and consider a sleep study if you snore or wake feeling unrefreshed. Get referred for CBT-I if available.
Chronic insomnia is usually not just stress. Treating it properly changes more than just sleep: it changes mood, cognitive function, pain tolerance, blood pressure, and metabolic health. Sleep is a vital sign, not a luxury.
Comments
Post a Comment