Why Can't I Sleep? 14 Common Causes and What to Do

When "Can't Sleep" Becomes a Pattern

Occasional poor sleep is normal. The average adult has 5-10 nights per year of significant difficulty sleeping, usually tied to stress events. When difficulty sleeping becomes frequent — more than three nights per week for more than three months — it meets clinical criteria for insomnia disorder and requires systematic intervention.

The most important step is identifying whether your sleep difficulty has a specific cause, because the fix depends entirely on the cause. Treating anxiety-driven insomnia with sleep hygiene alone will not work. Treating circadian rhythm disruption with relaxation techniques alone will not work.

14 Common Causes and What to Do

1. Irregular Sleep Schedule

Circadian rhythms are driven by consistent timing signals. Irregular sleep and wake times — especially sleeping in on weekends — destabilize the circadian phase and reduce sleep pressure predictability. The fix: commit to a consistent wake time, every day including weekends, for four weeks. This is the single highest-leverage behavioral change available.

2. Anxiety and Stress

Acute and chronic stress elevate cortisol and activate the sympathetic nervous system, creating physiological arousal incompatible with sleep onset. If anxiety is the primary driver, behavioral techniques (CBT-I, worry postponement, cognitive restructuring) address the root cause. Sleep hygiene changes alone do not address the cognitive hyperarousal component.

3. Caffeine After Noon

Caffeine blocks adenosine — the sleep-pressure hormone — for 5-7 hours per dose. A 200mg coffee at 2 PM leaves 100mg active at 7-9 PM. Switch the caffeine cutoff to noon or 1 PM and maintain it for two weeks before evaluating the effect. Genetic slow metabolizers may need to cut off by 10 AM.

4. Screen Use Before Bed

Blue-spectrum light from phones, tablets, and monitors suppresses melatonin production by up to 85%. But the more critical issue is content arousal: social media, news, email, and streaming drama activate the brain's threat and reward systems, creating cognitive arousal that persists for 30-60 minutes after the screen is off. End screen use 60-90 minutes before bed.

5. Too Much Time in Bed

Spending more time in bed than you actually sleep reduces sleep efficiency and weakens the association between bed and sleep. If you sleep 6 hours but spend 9 in bed, the solution is counterintuitive: reduce time in bed to 6.5 hours (sleep restriction therapy) to consolidate sleep and rebuild sleep efficiency.

6. Wrong Mattress Firmness

An unsupportive mattress creates pressure points that activate pain-sensing neurons throughout the night, generating micro-arousals even when you are not consciously aware of them. You wake feeling unrefreshed without knowing why. If you have back, hip, or shoulder pain on waking, mattress firmness is a likely contributor.

7. Bedroom Temperature Too Warm

Core body temperature must drop 1-3°F for deep sleep stages to occur. A bedroom above 70°F (21°C) prevents or interrupts this drop. Set room temperature to 65-68°F (18-20°C). A foam mattress with poor airflow can raise skin temperature even in a cool room — consider this if you sleep hot regardless of room temperature.

8. Alcohol Use

Alcohol is sedating but sleep-disrupting. It suppresses REM sleep in the first half of the night and causes rebound arousal in the second half as it metabolizes. Even 1-2 drinks impair sleep architecture. If you drink regularly and have trouble staying asleep after 3-4 AM, alcohol is a likely contributor.

9. Sleep Apnea

Obstructive sleep apnea causes breathing interruptions that generate micro-arousals hundreds of times per night. Signs include: loud snoring, gasping or choking sounds, morning headaches, excessive daytime sleepiness, waking unrested despite adequate time in bed. This requires medical diagnosis (polysomnography) and cannot be self-treated with behavioral interventions.

10. Conditioned Arousal

After several weeks of poor sleep, many people develop a conditioned response to the bedroom itself: the brain has learned to associate bed with wakefulness and activates arousal when you enter the bedroom. This explains why insomniacs often fall asleep easily on the couch but not in bed. Stimulus control therapy (get out of bed if you cannot sleep within 20 minutes) addresses this directly.

11. Restless Legs Syndrome

RLS causes uncomfortable urges to move the legs, particularly at rest and in the evening. It is underdiagnosed and frequently mistaken for general restlessness or anxiety. It has specific medical treatments. If you have leg discomfort that improves with movement and worsens at rest, raise this with a physician.

12. Napping

Long or late naps (after 3 PM) reduce adenosine levels and weaken sleep pressure, making nighttime sleep onset harder. If you cannot avoid napping, limit naps to 20 minutes before 1 PM. Power naps (10-20 minutes) do not significantly impair nighttime sleep drive; extended naps (60-90 minutes) do.

13. Medications

Dozens of common medications impair sleep: beta-blockers (suppress melatonin), SSRIs (increase sleep latency and REM suppression), corticosteroids, decongestants, and some blood pressure medications. If sleep problems began after starting a new medication, discuss timing adjustments with your doctor before stopping anything.

14. Blue Light and Circadian Disruption

Beyond melatonin suppression, late-night light exposure delays the entire circadian phase — shifting your biological clock later. After weeks of late-night screen use, your body genuinely wants to sleep at 2 AM, not 11 PM. A strict light curfew combined with morning bright light exposure (10-30 minutes outdoors within one hour of waking) is the evidence-based protocol for resetting a shifted circadian phase.

Internal Resources

• Insomnia Remedies That Actually Work
• Can't Sleep Due to Anxiety?
• Sleep Anxiety: Why It Happens
• Best Mattress for Insomnia 2026

Frequently Asked Questions