Written by the Nuvirox Research Team
Key points
- Your body clock is set largely by daylight, so when sunrise and sunset shift, the clock has to re-synchronize — and the lag feels like fatigue.
- Spring transitions tend to hit harder than autumn ones, partly because dawn moves fast and the clock resists advancing.
- Seasonal tiredness that tips into persistent low mood or major sleep disruption is worth raising with a clinician.
Short answer: your internal clock runs on daylight, and shifting seasons force it to recalibrate. As sunrise and sunset move, the circadian system that governs alertness, sleep, and hormone timing has to re-anchor to the new light schedule. During that adjustment window, your sleep and energy can feel off — which is the seasonal slump people describe.
Why does changing daylight make me tired?
Light is the master signal for your circadian clock. Morning light in particular tells your brain when 'day' begins, setting the timing of alertness, melatonin, and the cortisol rhythm that helps you wake. When seasonal daylight shifts — earlier or later dawn, longer or shorter days — your clock has to move with it, and until it catches up, your internal time and the external clock disagree. That mismatch is experienced as grogginess and low energy.
Why is spring worse than autumn for some people?
Because advancing the clock (getting up relatively earlier as dawn comes sooner, and around the spring clock change) is biologically harder than delaying it. Research on seasonal and daylight-saving transitions finds the clock adjusts readily to the autumn shift but resists the spring one — especially in night-owl chronotypes. If you already run late, you may feel the change most. This overlaps with why some people are tired in the afternoon but wide awake at night.
What the research shows
STUDY SNAPSHOT
| Dataset | ~55,000 people (chronotype database) |
| Finding | Sleep timing tracks the seasonal progression of dawn |
| Source | Current Biology, 2007 (PMID 17964164) |
The clock follows dawn. A large chronotype study found that on free days, people's mid-sleep timing tracks the seasonal movement of dawn under standard time — direct evidence that the human clock is tuned to the changing light of the seasons, and must shift as that light shifts.
Spring transitions disrupt more. The same line of research shows the clock readily adjusts to the autumn change but struggles to advance for the spring one, particularly in later chronotypes — fitting the common experience of a rougher spring adjustment.
When seasonal tiredness is more than an adjustment
If the fatigue lasts well beyond the transition, comes with persistent low mood, loss of interest, oversleeping, or appetite changes that recur the same time each year, that pattern is worth discussing with a clinician rather than waiting it out. Seasonal tiredness that re-syncs in a week or two is normal; a recurring, weeks-long mood-and-energy shift is a different conversation.
How to ease the transition
Get bright light early in the day — outdoors if possible — to anchor your clock to the new schedule faster. Keep consistent sleep and wake times through the change rather than drifting. Limit bright evening light, which pushes the clock later. These light-timing habits do more for circadian fatigue than any supplement; NAD+-pathway support is about cellular energy, not resetting your body clock. For the related travel version of this, see whether NAD+ helps with jet lag.
What people often notice
Seasonal-transition tiredness is something people describe every spring and autumn, and the reports cluster in telling ways. Around the spring clock change and the rapid lengthening of days, people often note a stretch of feeling jet-lagged without travelling — groggy mornings, off-kilter sleep, a few flat days. In autumn, the complaints shift toward earlier evening fatigue as light recedes. Both fit the body-clock-tracking-dawn explanation: the felt experience is the lag between your internal time and the new external light.
A common and reassuring observation is that it passes. People who push through the first week or two with consistent routines generally report their energy re-stabilizes, which matches the self-limiting nature of circadian re-entrainment. Those who lean into morning light tend to report a faster recovery — again, exactly what the science would predict.
Why light timing is the lever
Because light is the master signal, when you get it matters more than how much. Morning light pulls your clock earlier and helps you adapt to lengthening days; bright evening light pushes it later and prolongs the mismatch. People who get outside early in the transition window consistently describe an easier adjustment, while those glued to bright screens late often describe a dragged-out one. It’s the same circadian logic behind being tired by day and wired at night.
Altogether, seasonal fatigue is a short re-synchronization tax, not a lasting problem. Your daylight-driven clock simply needs a little time and the right light cues to catch up. Anchor your mornings with bright light, hold your sleep and wake times steady through the transition, and the slump usually clears within a week or two. The version that doesn’t — a recurring, weeks-long dip in mood and energy — is the one that warrants a conversation with a clinician.
Frequently asked questions
How long does seasonal fatigue last?
Usually days to a couple of weeks as your clock re-anchors to the new daylight. If it drags on much longer, or comes with low mood, that's worth a closer look.
Why do I feel it most in spring?
Advancing your clock is harder than delaying it, and dawn moves quickly in spring. Late chronotypes feel this most. The autumn shift is generally easier to absorb.
Does getting morning light really help?
Yes — early bright light is the strongest signal for re-setting your circadian clock to the new schedule, which is the core of the fatigue.
Can a supplement reset my body clock?
No — light timing and consistent sleep do that. Supplements that support cellular energy don't shift circadian timing.
FROM NUVIROX
Why we formulated NAD+ Restore
NAD+ Restore pairs 500 mg of Nicotinamide Riboside Chloride (NR) — one of the two most-researched NAD+ precursors, within the dose range used in published human trials — with 150 mg trans-resveratrol (from Japanese Knotweed) and 50 mg quercetin (from Sophora japonica), polyphenols studied alongside NAD+ pathways for cellular health support.
A small amount of galactomannans from fenugreek (10 mg) is included to support absorption. It is backed by a 60-day money-back guarantee — long enough to actually evaluate it the way the research says you should.
Learn more about NAD+ Restore →The bottom line
Seasonal tiredness is your daylight-driven body clock catching up to a new light schedule. The lag is real but usually short. Anchor yourself with early light and steady sleep times, and the slump passes. If it turns into a recurring, weeks-long dip in mood and energy, that's a reason to talk to your doctor.
References
- Kantermann T, Juda M, Merrow M, Roenneberg T. The human circadian clock's seasonal adjustment is disrupted by daylight saving time. Curr Biol. 2007;17(22):1996-2000. PMID: 17964164.
- Martens CR, Denman BA, Mazzo MR, et al. Chronic nicotinamide riboside supplementation is well-tolerated and elevates NAD+ in healthy middle-aged and older adults. Nat Commun. 2018;9(1):1286. PMID: 29599478.
- Puetz TW, Flowers SS, O'Connor PJ. A randomized controlled trial of the effect of aerobic exercise training on feelings of energy and fatigue in sedentary young adults with persistent fatigue. Psychother Psychosom. 2008;77(3):167-174. PMID: 18277063.
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. This article is for informational purposes only and is not a substitute for professional medical advice.