Can you "reprogram" your biological clock?

Partially. Chronotype (lark/owl) is largely genetically determined, and it cannot be radically changed. But the amplitude and stability of the circadian rhythm can be significantly improved through: consistent wake-up time, light signals, eating patterns, and physical activity. This is a "fine-tuning" of the clock, not a change of the mechanism.

Night shifts: How harmful are they in the long term?

Chronic night shift work is a proven risk factor for: cancer (especially breast cancer), cardiovascular diseases, type 2 diabetes, and depression. The WHO classifies circadian rhythm-disrupting shift work as a "probable carcinogen". If night shifts cannot be avoided, it is especially important to prioritize other health components (nutrition, physical activity, sleep in darkness).

Circadian Rhythms: How Your Internal Biological Clock Controls Your Health

Circadian rhythms regulate sleep, mood, immunity, and metabolism. Discover why disrupting your body clock is dangerous and how to maintain it.

🌿psybot.app·June 19, 2026·2 min read

Why is it harder for you to make decisions in the evening? Why do surgeons make more mistakes after midnight? Why do shift workers have a higher risk of diabetes? Why does flying across the ocean disrupt the body so much?

All of this is due to circadian rhythms. Biological clocks that govern almost every function of your body.

1. What are Circadian Rhythms

A circadian rhythm (from Latin circa dies — 'about a day') is a biological cycle lasting ~24 hours. They regulate:

Sleep and wakefulness
Body temperature
Hormonal rhythms (cortisol, melatonin, insulin)
Blood pressure
Immune system function
Cognitive performance
Metabolism

2. How Biological Clocks Work

The main pacemaker of rhythm is the suprachiasmatic nucleus (SCN) of the hypothalamus. It receives light signals directly from the retina via the retinohypothalamic tract.

Light (especially blue spectrum in the morning) → SCN → triggers daytime physiological processes. Darkness → SCN → initiates nighttime processes (melatonin release, temperature drop, transition to sleep).

The 2017 Nobel Prize in Physiology or Medicine was awarded precisely for the discovery of the molecular mechanisms of circadian rhythms (Jeffrey Hall, Michael Rosbash, Michael Young).

3. What Disrupts Circadian Rhythms

Irregular sleep and wake schedule
Bright light (especially blue spectrum) in the evening
Lack of bright light in the morning (working in an office without windows)
Eating at night
Night shifts
Jet lag

4. Consequences of Chronic Disruption

Chronic disruption of circadian rhythms is associated with:

Metabolic syndrome and diabetes
Cardiovascular diseases
Oncological diseases
Depression and anxiety
Immune disorders
Cognitive decline

5. How to Support Circadian Rhythms

Consistent wake-up time (every day)
Bright light in the morning (a walk or a 10,000 lux lamp)
Darkness and dim light in the evening
Eating during the day, not late in the evening
Physical activity in the morning or afternoon

Read also: Sleep Hygiene. Discuss with our AI psychologist psybot.app.

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