Evidence: Strong

Clinical guidelines, meta-analyses or several good trials agree. How we rate evidence.

AlcoholAlcohol can help you fall asleep, then breaks up the second half of the night, cuts REM sleep, raises your heart rate and lowers HRV. Less, and earlier, is better.
- Evidence: Strong
- Medium effort
- Free
- Works: tonight
Caffeine cutoffHave your last coffee at least 9 hours before bed. Caffeine cuts sleep and deep sleep even when you fall asleep fine.
- Evidence: Strong
- Low effort
- Free
- Works: tonight
How sleep worksTwo systems decide when you get sleepy and how deeply you sleep. Almost every tip on this site works through one of them.
- Evidence: Strong
- Low effort
- Free
- Works: 1 week
Sleep restrictionSpend less time in bed so the time you do spend is asleep. A core part of CBT-I, with clear rules and real side effects.
- Evidence: Strong
- High effort
- Free
- Works: 3–4 weeks
Sleep stages and cyclesLight, deep and REM sleep, why deep sleep comes early and REM comes late, and why "90-minute cycles" aren't precise.
- Evidence: Strong
- Low effort
- Free
- Works: tonight
What "good sleep" meansEnough hours, falling asleep without a fight, few wake-ups, regular times, and feeling alert in the day.
- Evidence: Strong
- Low effort
- Free
- Works: 1 week