Every intervention, ranked.

Anyone photosensitive, on photosensitising medication, or with an eye condition should ask a clinician first.

• Most trials use light boxes or measured lux, not 'go outside', so the dose you actually get varies with weather, season and latitude.
• The '10–20 minutes' is a practical extrapolation from the phase-response curve's shape, not a measured protocol — the studies measure illuminance and timing, never minutes outside. Overcast days honestly need longer.

People already sufficient on a 25-OH D test gain little from more pills; megadoses have been harmful in trials.

Anyone with existing neck pain who is treating a laptop stand as the fix. For symptomatic office workers, the intervention with actual meta-analytic support is neck and shoulder strengthening exercise, not workstation adjustment. Skip this too if you would be buying an expensive monitor arm on the promise of pain relief — the posture change is real, the pain relief is not established, and a stack of books plus a $25 keyboard delivers the same measured effect. Also not a substitute for addressing workload, task variation and time-on-screen, which is where the prospective evidence actually points.

• No trial has shown that raising the screen reduces neck pain. The evidence is that it reduces neck flexion angle and neck-extensor muscle activity — a mechanism, not an outcome. The Cochrane review's single workstation-adjustment trial found no effect on pain or discomfort at all.
• The strongest direct study of this exact setup (riser plus external keyboard) used 20 healthy young men doing two eight-minute sessions per condition. A quarter of an hour cannot tell you anything about a symptom that develops over months, and an all-male sample of healthy young volunteers does not represent the people who actually have neck pain.

Anyone treating a diagnosed condition. Seasonal affective disorder is managed with light-box therapy at specified intensity, duration and timing — a different intervention with its own trial evidence, which none of these papers tests. Do not read this as a substitute for prescribed light therapy, or for treatment of a diagnosed sleep or mood disorder. People with photosensitivity, photosensitising medication, lupus, or a personal or family history of skin cancer should take medical advice on sun exposure before increasing it. Shift workers are explicitly outside this evidence — the wearable light-logger study recruited only people without shift work or jetlag — and daytime light advice can be actively wrong when the work schedule is nocturnal.

• Nobody has trialled this. There is no study — randomised or otherwise — of taking a laptop outside to work. Every paper here tests something adjacent: camping for a week, having a window, self-reported hours outdoors, or wearing a light sensor. The inference from those to 'work outside this afternoon' is ours, not the literature's.
• The camping study moved the clock, not sleep itself. Melatonin timing shifted about two hours earlier, but weekly sleep duration (6.7 versus 6.8 hours) and sleep efficiency (87.6% versus 87.0%) did not change at all, and no mood or wellbeing outcome was measured. Read it as evidence about circadian timing, not as evidence you will sleep more or feel better.

Unstable angina, recent heart attack, severe aortic stenosis, and pregnancy are standard reasons to skip a hot sauna; alcohol plus heat is a documented way to die in one.

Unsupervised cold water is a bad idea for anyone with heart disease, arrhythmia, or who cannot get out quickly — cold shock can kill before hypothermia does.