Why is daylight savings time bad for our health?

Daylight saving time can harm health by shifting the clock time without shifting the sun, disrupting circadian rhythms and throwing light and sleep cues out of alignment. 1

• 1. One-hour shift: Even a one-hour change can be difficult to adjust to; the disruption can accumulate across sleep timing and light’s direct effects on mood. 2
• 2. Routine changes compound it: When the clock change is layered onto existing sleep deprivation and already-misaligned routines, the effects can add up; the discussion also emphasizes keeping light, food, and exercise cues consistent. 3 4
• 3. Nighttime light and dopamine: Bright light exposure at night—especially between about 11 p.m. and 4 a.m.—can suppress dopamine, which may negatively affect mood and inhibit learning. 5
• 4. Keep light cues regular: Morning and late-afternoon or evening sunlight help anchor the circadian clock; dimming lights at night and avoiding bright light then can help keep rhythms aligned. 6 7