Single questions, honestly answered.
Each brief takes one question about sleep, light, timing, or the things people say about them, and works through it: what the evidence looks like, who it was measured in, and what is still open. Where the answer is "we do not know yet", the brief says that.
All research briefs
No briefs published yet
The first briefs are in review. A brief does not publish until its sources are in place, so this page stays empty rather than filling with claims we cannot yet point at.
What the ratings mean.
Strong
A well-described mechanism supported by repeated findings across independent groups, measured in people, with results that point the same direction. New work is unlikely to reverse it.
Moderate
A real effect, consistent enough to be useful. How large it is, how long it lasts, or which people it was measured in still leaves real room to move.
Limited
Thin. Small studies, short follow-up, a single group, or a stand-in measurement rather than the outcome you actually care about. Plausible and under-tested.
Mixed
Credible work disagrees, and the disagreement has not resolved. Different methods, populations, or definitions produce different answers.
Insufficient
There is research, and it does not answer the question either way. Often because the thing being asked about cannot yet be separated from something it travels with.
Not studied adequately
Nobody has properly looked, at least not in people. Animal work, laboratory models, and confident popular repetition all sit here until a human study exists.