Morning mood dips follow biological time

Controlled lab measures show anxiety‑like and depression‑like mood peak in the biological morning (around internal 8–9am) even when external routines are held constant, implying that mood varies predictably with circadian phase. Circadian misalignment from shift work, social jetlag or evening light shifts these biological times and can therefore produce chronic mood vulnerability rather than just transient tiredness. — If robust, this reframes workplace and school scheduling, and timing of mental‑health interventions, as circadian policy levers for population mental health.