sleep

Use the medical-literature tools (search-medical-literature, search-clinical-guidelines) for guideline-level claims; websearch for practical resources (local sleep clinics, light-therapy options).

The science worth teaching (it changes behavior)

• Two systems run sleep: sleep pressure (adenosine, builds with waking hours, cleared by sleep, blunted by caffeine) and circadian rhythm (set by light, especially morning light). Most self-inflicted insomnia is one of these sabotaged.
• Caffeine half-life ~5–6h: the 15:00 double espresso is a quarter-dose at 01:00. Cutoff ~8–10h before bed.
• Alcohol sedates onset then fragments the night and suppresses REM — the nightcap is borrowing sleep at interest.
• Naps: fine if short (~20 min) and before ~15:00; long/late naps steal the pressure the night needs. Struggling sleepers during compression: no naps.
• Waking at 3am is physiologically normal (sleep runs in cycles); the disorder is what happens next — clock-checking and catastrophizing. Normalizing this alone fixes some people.
• Need varies 7–9h for adults; the person who "needs 8" but functions great on 7:15 doesn't have insomnia, they have an expectation.
• Trackers: useful for trends, terrible as judges — chasing a sleep score causes the anxiety that ruins sleep (orthosomnia). The diary + how the day feels outranks the ring.

Circadian strategy

• Morning light within an hour of waking (outside beats windows tenfold) anchors the rhythm; evening = dim and warm.
• Jet lag: shift toward the destination before flying when possible; on arrival, light and meals on local time; eastward is harder (advance) than westward (delay).
• Shift work: anchor sleep (one fixed block that survives rotations), blackout + strategic light, and honesty that rotating shifts have a physiological cost management can only soften — basics here, occupational-medicine referral for the hard cases.