Sleep Hygiene: What Actually Works (and What Doesn't)

Sleep hygiene is the term for the habits and environmental conditions that support good sleep. It's one of the components of CBT-I — the clinical treatment for insomnia — and it's also the part most people have heard of.

The problem is that most sleep hygiene advice is simplified to the point of being useless. 'Avoid screens.' 'Don't drink coffee.' 'Keep a regular bedtime.' These aren't wrong — but they're incomplete, and on their own, they rarely fix chronic insomnia.

Here's what the evidence actually supports, and how much each habit matters.

The rules that matter most

• ✓Keep a fixed wake time, every day — This is the single most important sleep hygiene rule and the most ignored one. Getting up at the same time every morning — weekends included — anchors your circadian rhythm and builds consistent sleep pressure. Sleeping in at weekends feels like a reward but it shifts your internal clock and makes Monday harder. The wake time matters more than the bedtime.
• ✓Control light exposure — Light is the primary signal your brain uses to set its internal clock. Bright light in the morning (ideally outdoors, within an hour of waking) advances your circadian rhythm and makes you sleepier earlier. Blue-light avoidance in the 60–90 minutes before bed reduces melatonin suppression. Dimming all lights in the evening, not just screens, is more effective than blue-light glasses.
• ✓Watch alcohol carefully — A drink in the evening can help you fall asleep faster, which is why people use it. But alcohol fragments the second half of sleep — the REM-heavy portion — producing lighter, more disrupted sleep from around 2–4am. If you're waking in the night, evening alcohol is one of the most common culprits.
• ✓Keep the bedroom cool — Core body temperature needs to drop to initiate sleep. A bedroom temperature of 16–18°C is the clinical recommendation. Rooms that are too warm (especially above 20°C) consistently produce more fragmented sleep in studies. This is one of the easiest environmental changes to make.
• ✓Caffeine timing — Caffeine's half-life is around 5–6 hours, meaning half of a 3pm coffee is still active at 8–9pm. The effect varies significantly by individual metabolism, but for most people, stopping caffeine by 1–2pm produces meaningful improvement in sleep quality. Don't forget that tea, green tea, cola, and pre-workout supplements all contain caffeine.

What matters less than people think

Screens before bed — The blue light from phones suppresses melatonin slightly, but the effect is smaller than commonly claimed. The bigger issue is the cognitive stimulation — checking social media, reading news, or watching tense content activates your nervous system regardless of the light spectrum. If you're going to use your phone before bed, passive, low-stimulation content matters more than the blue-light filter.

Herbal supplements — Valerian, chamomile, passionflower, and similar products have very limited clinical evidence for insomnia. The effect sizes in trials are small and inconsistent. They're unlikely to cause harm but shouldn't be expected to treat chronic insomnia.

The '8 hours' rule — Sleep need varies genuinely between people. Most adults need 7–9 hours, but individuals at both ends of that range are not disordered. What matters is how you feel during the day, not hitting a specific number. Anxiety about getting exactly 8 hours is itself a driver of insomnia.

Why sleep hygiene alone rarely cures insomnia

Sleep hygiene is a foundation, not a cure. For people with acute insomnia (poor sleep triggered by a specific stressor), improving sleep hygiene can be enough. For chronic insomnia — ongoing sleep problems for more than 3 months — it's rarely sufficient on its own.

The reason is that chronic insomnia is maintained by two mechanisms sleep hygiene doesn't address: conditioned arousal (your brain has learned to associate bed with wakefulness) and hyperarousal (ongoing activation of the stress response at bedtime). These require the other components of CBT-I — particularly sleep restriction and cognitive restructuring — to resolve.

Think of sleep hygiene as the soil. CBT-I is the full programme. The soil matters, but it's not enough without the rest.

Where to start

• ✓Fix your wake time first. Pick a time you can hit every day — including weekends — and commit to it for 2 weeks before changing anything else.
• ✓Audit your alcohol. Track when you drink and when you wake. Most people are surprised by the correlation.
• ✓Cool your bedroom. A thermometer and an open window or a fan are a meaningful sleep intervention, not just a comfort preference.
• ✓Build a wind-down. Your body needs a transition between the active day and sleep. 30–60 minutes of consistently calm activity before bed — same time, same routine — signals to your nervous system that sleep is coming.