The Evening Light Paradox: Does the Mental Health Boost of BST Outweigh the Physical Cost?

By Mark Phillips Founder at Sleep Well Hub | Certified Sleep Practiconer & NLP Master Hypnotherapist

When the clocks go forward for British Summer Time (BST), around the world these time shifts are known as Daylight Saving Time (DST), a familiar debate ignites.

On one side, there is the undeniable joy of lighter evenings the promise of summer, more time for outdoor activities, and a palpable lift in national mood. On the other side, there is the biological reality of losing an hour of sleep and the subsequent disruption to our circadian rhythms.

Recently, following a post on the Sleep Well Hub Essex Facebook page, many of you shared that the lighter evenings significantly improved your mental health. This is a completely valid and common experience. However, as an educator and practitioner in sleep health, I must ask the critical question:

Does this psychological "feel-good" factor offset the physiological detriment of circadian disruption?

Let’s explore the science behind the "Evening Light Paradox."

 The Perception:

Why Evening Light Feels So Good

The psychological benefits of evening daylight are easy to understand. Lighter evenings provide more opportunities for socialising, exercising outdoors, and simply enjoying the end of the day. This can lead to a subjective feeling of improved wellbeing and a reduction in the "winter blues."

However, this perception often masks what is happening beneath the surface. While we feel better, our biology is experiencing a state of confusion known scientists call social jet lag.

The Reality:

The Biological Cost of Evening Light

Our internal body clock, the suprachiasmatic nucleus (SCN), relies on light to stay synchronised with the 24-hour day. But not all light is created equal.

1. The Essential "Morning Anchor"

Morning light is the primary "zeitgeber" (time-giver) that anchors our circadian rhythm. Exposure to bright light in the hour after waking speeds up the circadian cycle (a phase advance), helping us feel alert during the day and sleepy at night [1].

When BST shifts the social clock forward, we lose this crucial morning light. We are forced to wake up in the dark, which fails to properly reset our internal clock, leading to increased cortisol levels and stress [2].

2. The Suppressive Effect of Evening Light

Conversely, evening light—especially at high intensities—suppresses the production of melatonin, the hormone that signals to our body that it is time to sleep. This delays the circadian clock (a phase delay), making it harder to fall asleep at a reasonable time and leading to chronic sleep deprivation [3].

As Jamie Zeitzer, a researcher at Stanford Medicine, succinctly explains: "You generally need more morning light and less evening light to keep well synchronized to a 24-hour day" [2].

 The Trade-Off: Mental Health vs. Physical Health

When we compare the subjective mental health benefits of evening light against the objective physical costs of circadian disruption, the scientific consensus is clear.

The Mental Health Nuance

While evening light is pleasant, studies show that morning light has a far more robust clinical effect on treating depression and Seasonal Affective Disorder (SAD). Research indicates that individuals with high morning light exposure have a 17% to 34% lower mortality risk and significantly better mental health outcomes than those who rely primarily on evening light [4].

The Physiological Toll

The "mood boost" from evening light does not mitigate the physical stress placed on the body by circadian misalignment. The evidence is stark:

•        Cardiovascular Risk: A prominent study found a 24% increase in heart attacks on the Monday following the start of BST [5].

•        Metabolic Consequences: Chronic circadian misalignment is linked to increased rates of obesity, stroke, and metabolic disorders [2].

•        Road Safety: The combination of morning darkness and sleep deprivation leads to a 6% to 16% increase in road traffic collisions in the days following the clock change [6].

The Scientific Verdict:

Borrowing Happiness from Future Health

The consensus among chronobiologists and organisations like the British Sleep Society is that the subjective psychological benefit of evening light is not enough to offset the objective physiological detriment [7]. By imposing this artificial shift, we are essentially sacrificing long-term systemic health for a short-term psychological preference.

The British Sleep Society strongly recommends the abolition of the twice-yearly clock changes, advocating for permanent Standard Time (GMT) because morning light is crucial for maintaining the optimal alignment of our body clocks [7].

What You Can Do?

If you enjoy the lighter evenings, by all means, use them to stay active and socialise. However, do not neglect the biological necessity of morning light.

My Expert Advice: The real mental and physical health medicine is getting outside for 15 to 20 minutes as soon as the sun comes up. This "Morning Anchor" will reset your circadian rhythm, improve your sleep quality, and protect your long-term health.

My Expert Opinion: While you might trigger your own circadian misalignment by staying up later at night or getting up earlier than is normal for you (and lets be honest we all do it at times, you make that choice) you then give yourself social jet lag and you might feel it the next day or two, but your body is building up the damage over a lifetime. But you now understand the risk to yourself. You can make an informed choice and take action to minimise the effects on your body.

However, the only reason we now have awareness of the physical impacts on each one of us, is because around the world we do these artificial clock movements to massive numbers of people all at the same time, so we see the impact in A&E departs from these accumulative results. Currently nearly 1.5 billion people physically suffer from these biannual clock movements. The list of countries who have moved away from Daylight Saving Time is growing annually, since 2014 ten counties have stopped, Daylight Saving Time (DST) taking some 716 million people out of this unnecessary risk of physical harm. EU, USA and Canada have all voted to abolish DST, but the legislation is bogged down in parliamentary procedure. UK has not got as far as a parliamentary vote yet.

I Do Hope You Sleep Well, and stay sharp.

By Mark Phillips Founder at Sleep Well Hub | Certified Sleep Practiconer & NLP Master Hypnotherapist

22 years Army | 14 years Police | 10 Years plus as Sleep Workshop Facilitator

Contact Sleep Well Hub:

•        Website: www.sleepwellhub.co.uk

•        Email: mark@sleepwellhub.co.uk

•        WhatsApp 07939 557029

Trust the science, not social media

References

[1] Sleep Foundation. (2023). "Light and Sleep: Effects on Sleep Quality.

[2] Stanford Medicine. (2025). "Study suggests most Americans would be healthier without daylight saving time.

[3] Manfredini, R., et al. (2018). "Daylight saving time, circadian rhythms, and cardiovascular health.

[4] NPR / Shots Health News. (2024). "Getting more light in the day and less at night is good for your health.

[5] Michigan Medicine. (2017). "Why Daylight Saving Time Could Increase Your Heart Attack Risk.

[6] Czeisler, C. A. (2022). "Tips to Help Adjust Sleep for Daylight Savings." Harvard Medical School.

[7] Northumbria University. (2024). "Sleep experts call for UK to abolish twice-yearly clock changes.