I can't fall asleep — what's actually happening
Updated 15 May 2026
1 · What this actually is
Short answer
Difficulty initiating sleep — taking longer than 20–30 minutes to fall asleep after lights-out, most nights, despite adequate opportunity. Clinically, this becomes sleep onset insomnia when it occurs three or more nights a week for three months or more, with daytime impact.
2 · Most likely causes
- 1
Conditioned arousal
Your bed has become associated with not sleeping — lying awake, frustrated. The cue itself now triggers wakefulness. This is the single most common driver of chronic onset insomnia.
- 2
Cognitive hyperarousal
Racing thoughts, planning tomorrow, replaying conversations. The mind is too active to allow sleep onset.
- 3
Circadian timing mismatch
You're trying to fall asleep before your biological 'sleep window' opens. Common in evening chronotypes forced onto early schedules.
- 4
Stimulant or alcohol timing
Caffeine has a 5-hour half-life on average. Alcohol shortens onset latency for some but rebounds with fragmented sleep.
- 5
Acute stress
A recent stressor — work, relationship, health — produces short-term onset difficulty that usually resolves but can become chronic if not managed.
3 · What the evidence says works
CBT-I (Cognitive Behavioural Therapy for Insomnia)
First-line treatment per AASM, NICE, and every other major guideline. Combines stimulus control, sleep restriction, and cognitive restructuring. Effective in 70–80% of chronic insomnia cases.
Evidence: strong
Stimulus control
Bed is for sleep and sex only. Leave the bed if you can't sleep within ~20 minutes. Return only when sleepy. Re-conditions the bed-sleep association.
Evidence: strong
Sleep restriction therapy
Temporarily reduce time in bed to consolidate sleep and rebuild sleep drive. Counterintuitive but evidence-supported. Usually done under guidance.
Evidence: strong
Bright morning light
Reinforces your circadian rhythm and indirectly improves evening sleepiness. Free, no side effects, strong evidence.
Evidence: strong
Sleep medication (zolpidem, eszopiclone)
Effective short-term. Loses effect over weeks. Not recommended for chronic insomnia by current guidelines except as adjunct.
Evidence: moderate
Melatonin (low-dose, timed)
Effective for circadian phase delay (evening chronotype). Less effective for primary onset insomnia. 0.3–1 mg, 4–5h before target bedtime.
Evidence: moderate
4 · What doesn't work
Common claims, ranked by reality
Claim
You need to make up the sleep you missed.
Reality
Trying to 'catch up' usually extends time in bed and worsens conditioned arousal. Stick to a consistent wake time even after a bad night.
Claim
Magnesium fixes insomnia.
Reality
Likely helps only if you're deficient. The effect in non-deficient adults is small and trial evidence is weak.
Claim
Tracking your sleep helps you sleep better.
Reality
Sleep trackers can worsen 'orthosomnia' — anxiety-driven insomnia from sleep data itself. Useful for trends, harmful for the chronically anxious.
Claim
You just need better sleep hygiene.
Reality
Sleep hygiene alone is rarely sufficient for chronic insomnia. CBT-I outperforms it consistently in head-to-head trials.
5 · When to see a doctor
Book an appointment with a GP — and consider asking about a sleep study — if any of these apply:
- Onset difficulty has persisted three nights a week or more for three months or more.
- You snore loudly, gasp, or have been told you stop breathing in your sleep.
- Insomnia is paired with significant low mood, anxiety, or suicidal thoughts.
- You have legs that ache or compel movement when trying to settle.
- You're already on sleep medication and it's losing effect.
Common follow-up questions
- How long should it take to fall asleep?
- Healthy sleep onset latency is roughly 10–20 minutes. Under five minutes can paradoxically signal sleep deprivation. Over 30 minutes most nights, for months, is the threshold for clinical concern.
- Will sleep hygiene alone fix chronic insomnia?
- Rarely. Sleep hygiene is a useful baseline, but the evidence consistently shows that CBT-I outperforms hygiene alone for chronic insomnia. If hygiene improvements haven't worked after a few weeks, escalate.
- Is melatonin worth trying?
- For circadian-shifted insomnia (your sleep window is biologically later than your desired bedtime), low-dose timed melatonin has reasonable evidence. For primary onset insomnia without a circadian component, the evidence is weak.