Sun, Serotonin and Mood: How Light Influences the Mind
Why do you feel like a different person in July than in November? Part of the answer may run through your eye, not your skin. This article separates two pathways of sunlight that are often confused: light, the internal clock and serotonin on one side, vitamin D on the other.
We say "the sun does you good" and mostly mean vitamin D. Yet the light that can reach your mood fastest does not land on your skin, it lands in your eye. If you keep these two pathways apart, you can use the sun more wisely and respect it at the same time.
I bet you know this moment. After three grey weeks, the sky breaks open. You step outside, squint, and something inside you straightens up. Your shoulders drop. Your breathing deepens. Suddenly you feel like calling someone.
And then you may also know the opposite. November, four in the afternoon, and dusk is already falling. You are not ill. But everything feels a little muted, as if someone had turned the dial for joy of life down a few notches.
Is it imagination? Is it just a weather mood? Or is there biology behind it? The short answer: there is a good deal to suggest that light may act on your mind through several pathways. And the best known pathway, vitamin D, is probably not the fastest.
This article describes how light may influence mood. It does not replace an assessment for depression. If you have felt down for weeks, can barely feel joy anymore, or have thoughts of no longer wanting to live, please talk to your family doctor, a psychotherapist or a psychiatrist. In Germany, the Telefonseelsorge can be reached free of charge around the clock at 0800 111 0 111 and 0800 111 0 222. In acute danger, call the emergency number 112.
What to expect here
- Why some people blossom in summer
- Two pathways: eye and skin
- Melanopsin, the light sensors for mood
- Serotonin in summer and in winter
- What large population data show
- Vitamin D in honest perspective
- Endorphins from the skin
- Thinking sun protection and light together
Why do I blossom in summer?
Before we dive into neurobiology, I want to tell you about a pattern I encounter again and again in my practice.
"In July I'm a different person"
I know this pattern very well. A middle-aged woman who spends much of her working day at a screen came to see me for something else entirely. At the end of our conversation, she said a sentence that stayed with me.
Together we looked at her everyday life, not at a diagnosis. What stood out: in winter she left the house in the dark in the morning and came home in the dark. On workdays she saw almost no daylight. In summer, by contrast, she had breakfast on the balcony and cycled to the office.
The turning point was not a supplement but a thought. Until then she had connected the sun only with skin and vitamin D. That bright light at the eye can be a signal of its own for the internal clock was new to her. Afterwards, in autumn, she deliberately built morning daylight into her way to work.
She described the following winter as somewhat less heavy. I cannot claim causality, but I document the temporal association. More movement outdoors, a mild winter and knowing her own pattern may just as well have played a part.
The lesson: Sometimes change begins with understanding the pathway through which your own body responds to light.
Her question is one of the most common I hear about the sun. Is it vitamin D? The honest answer: probably only to a smaller extent. To understand why, we need to keep two pathways of sunlight apart.
Blossoming in summer is not a sign of moodiness. It may be a hint that your nervous system responds particularly sensitively to light.
This sensitivity is not a weakness. It is information you can use.
And now you know why, when someone asks me about the sun, I always first want to know when and how much daylight they actually see.
Two pathways of sunlight: eye and skin
Imagine the sun as a letter sent to two different addresses. One address is your eye. The other is your skin. Both letters come from the same sender. But they have very different contents and land in very different departments of your body.
Light through the eye
- Visible light, especially the blue part
- Special sensors in the retina
- Target: internal clock, melatonin, serotonin system
- Can be noticeable within hours to days
- Does not need direct sun on the skin
UV radiation through the skin
- UVB part of sunlight
- Vitamin D production in the skin
- Possibly endorphins from skin cells
- Vitamin D builds up over weeks
- At the same time a source of skin cancer risk
Why does this separation matter so much? Because in everyday life the two are constantly mixed up. Many people take a vitamin D capsule in autumn and think that settles the sun question. Others avoid every minute outdoors out of fear of skin cancer and lose the light signal for their brain in the process.
I don't see an either-or here. Both pathways have their own logic, their own studies and their own limits. Let's look at them one after the other.
A vitamin D capsule does not reach your retina. And a daylight lamp generally does not produce vitamin D in your skin.
If you treat both as the same thing, you may be replacing exactly the building block that could be more relevant for your mood.
And now you know why I always speak of two pathways when it comes to sun and the mind, not of one.
Pathway 1: How light reaches mood through the eye
Do you know the feeling of being more awake all day after a morning outdoors? That is not your imagination. Your eye does not only have the job of seeing images. It also constantly measures how bright it is.
In the retina, besides the familiar rods and cones, there are special cells. Experts call them intrinsically photosensitive retinal ganglion cells, ipRGCs for short. They contain a light pigment called melanopsin. Picture them as tiny light meters that do not take pictures but answer just one question: is it day or night right now?
Light hits the retina
Melanopsin cells respond especially to bright, blue-rich light, which is abundant in daylight.
Signal to the internal clock
Through a dedicated nerve pathway, the signal travels to the suprachiasmatic nucleus in the hypothalamus, your body's pacemaker.
Hormones adjust
The night hormone melatonin is suppressed, and the day-night rhythm of cortisol and body temperature can synchronize.
Mood networks
In animal models, these light signals also reach brain regions involved in mood and drive.
A team led by Samer Hattar and King-Wai Yau at Johns Hopkins University showed in rats and mice in 2002 that melanopsin is located in a small group of retinal ganglion cells. These very cells were light-sensitive themselves and sent their projections to the internal clock in the brain.
What this means for you: your eye probably has a system of its own that is not for seeing but for keeping time. This work comes from animal models, but it is considered a foundation of our current understanding of how light acts on the internal clock.
Hattar S et al. Science. 2002;295(5557):1065-1070. DOI: 10.1126/science.1069609In 2012, Tara LeGates and colleagues exposed mice to an irregular light cycle that changed neither the amount of sleep nor the internal clock. Even so, the animals showed more depression-like behavior and learned less well. In mice lacking the melanopsin cells, this effect did not occur.
This suggests that light might influence mood through these cells, and not only indirectly via sleep. In humans, this direct pathway has not yet been conclusively demonstrated. But it helps explain why the light signal at the eye can carry so much weight.
LeGates TA et al. Nature. 2012;491(7425):594-598. DOI: 10.1038/nature11673How this pacemaker ticks in detail, and why morning light in particular may be so important, I describe at length in my article on chronobiology and morning light. The counterpart, why bright screen light in the evening can push the clock in the wrong direction, you will find in the article on blue light and the circadian rhythm.
For your brain, light is not just something to see by. It is time-of-day information and perhaps also a mood signal.
If you spend the whole day indoors, your brain may perceive an endless twilight, even when the sun is shining outside.
And now you know why, when it comes to light and mood, I think of the retina first and only then of the skin.
Serotonin in summer and in winter
Serotonin has a reputation as a happiness hormone. That is a simplification. A different image fits better: serotonin is more like the background hum of a calm, stable temperament. It is involved in mood, sleep, appetite and impulse control. What is fascinating is that this system apparently swings along with the seasons.
In 2002, Gavin Lambert and his team at the Baker Heart Research Institute in Melbourne drew blood from 101 healthy men directly from the veins draining the brain. They measured a breakdown product of serotonin there and compared it with season and weather. Serotonin turnover in the brain was lowest in winter, and production rose with the duration of bright sunshine on the day of measurement.
Particularly remarkable: the association depended on the hours of sunshine on that particular day, not on temperature. This is an observational study in men and not proof of cause. But it supports the idea that bright light might engage the serotonin system fairly quickly.
Lambert GW et al. Lancet. 2002;360(9348):1840-1842. DOI: 10.1016/s0140-6736(02)11737-5Between 1999 and 2003, Nicole Praschak-Rieder and her team in Toronto used an imaging method, PET, to examine the brains of 88 healthy people. In autumn and winter, serotonin transporter binding was higher in all brain regions studied than in spring and summer. The fewer the hours of sunshine, the higher the values.
The transporter works like a vacuum cleaner that sucks serotonin back out of the gap between two nerve cells. More vacuum cleaners could mean less serotonin available for signaling. What this means for you: your serotonin system seems to be set differently in the dark half of the year, and here this applied to healthy people, not only to people with depression.
Praschak-Rieder N et al. Arch Gen Psychiatry. 2008;65(9):1072-1078. DOI: 10.1001/archpsyc.65.9.1072Both studies measured healthy people. That matters. They do not describe a disease, but a normal oscillation that is stronger in some people than in others. When this oscillation tips into a genuine low every year, experts speak of seasonal affective disorder. I have written a separate article on this: Winter depression and lack of light.
Well established: Light at the eye sets the internal clock. Mood and energy fluctuate with the seasons in many people.
Mechanistically plausible, human studies still small: that bright light stimulates serotonin turnover and that the serotonin transporter fluctuates seasonally.
My view through the KPNI lens: I understand sun-related mood as an interplay of the internal clock, serotonin and lifestyle. This is a reasoned perspective, not a conclusively proven theory.
If you feel more subdued in winter, that is not automatically a problem that needs treatment. It may be a biological season within you.
The question is not whether you fluctuate. The question is how strongly, and whether winter takes away your quality of life in the process.
And now you know why a sunny day in February can sometimes feel like a small restart.
What large population data show about daylight
How many hours were you outside in daylight yesterday? Not in the car, not behind the office window, but really outside? For many people, the honest answer is alarmingly small.
In 2021, Angus Burns, Sean Cain and colleagues at Monash University analyzed data from the UK Biobank. Participants spent a median of 2.5 hours a day outdoors in daylight. Each additional hour was associated with a lower likelihood of lifetime depression, less antidepressant use, less frequent low mood and anhedonia, and more reported happiness.
Sleep and rhythm also looked more favorable: easier waking, less frequent tiredness, fewer sleep problems and an earlier chronotype. This is an observational study based on self-reports and cannot prove cause. The authors nevertheless see low daylight exposure as a potentially important environmental factor for mood and sleep.
Burns AC et al. J Affect Disord. 2021;295:347-352. DOI: 10.1016/j.jad.2021.08.056In 2023, the same research group examined almost 281,000 UK Biobank participants to see whether genes influence how strongly daylight shifts the chronotype. The researchers found a first genetic variant and indications of genes that are active in the retina and in clock neurons.
What this means for you: people seem to differ in their sensitivity to light. That could explain why one person truly blossoms in summer while another barely notices the difference. Research on this, however, is still at a very early stage.
Burns AC et al. Sleep. 2023;46(3):zsac287. DOI: 10.1093/sleep/zsac287One thought that matters to me here: outdoor daylight, even on an overcast day, is usually many times brighter than a well-lit office. Your eye registers this difference, even if to you it just feels like a grey sky.
We have turned light into a question of weather. For your brain, it is more a question of where you are.
A grey day outdoors can mean more light for your internal clock than a sunny day behind glass.
And now you know why, with low moods, I almost always ask how much time someone really spends outdoors.
Pathway 2: Vitamin D in honest perspective
Less sun, less vitamin D, worse mood. This equation sounds so logical that almost nobody questions it. Perhaps you yourself have reached for the capsule in October, hoping to hold on to a little bit of summer. The evidence, however, is considerably more mixed than this logic would suggest.
Vitamin D is produced when UVB radiation hits the skin. It is actually more of a hormone than a vitamin and has receptors in many tissues, including the brain. A measured deficiency is therefore a real issue. The only question is how much of mood it explains.
In the VITAL-DEP trial, Olivia Okereke and colleagues in Boston studied 18,353 adults aged 50 and over who received vitamin D3 or a placebo for a mean of 5.3 years. The risk of developing depression or clinically relevant depressive symptoms did not differ between the groups, and mood scores did not change differently either.
At baseline, participants had no relevant depressive symptoms, and they were not specifically selected for deficiency. What this means for you: a vitamin D capsule does not appear to protect mood preventively in people without depression.
Okereke OI et al. JAMA. 2020;324(5):471-480. DOI: 10.1001/jama.2020.10224In 2022, a Finnish-Australian team led by Tuomas Mikola pooled forty-one placebo-controlled trials. Overall, vitamin D showed a small to moderate effect on depressive symptoms. However, the studies varied greatly, the risk of bias was concerning in many of them, and the certainty of the evidence was rated as very low.
What this means for you: there are indications of a benefit, especially in certain groups, but no solid basis for seeing vitamin D as a mood remedy for everyone.
Mikola T et al. Crit Rev Food Sci Nutr. 2023;63(33):11784-11801. DOI: 10.1080/10408398.2022.2096560In 2024, a team at the University of Tehran led by Shadi Ghaemi analyzed thirty-one randomized trials. Vitamin D was associated with somewhat lower depressive symptoms, more clearly in people who already had symptoms. Trials lasting up to 24 weeks showed an effect, whereas trials lasting more than a year did not.
No effect was found on anxiety symptoms. What this means for you: the benefit might lie mainly in existing complaints and more in the short term, which still needs to be confirmed in high-quality studies.
Ghaemi S et al. Psychol Med. 2024;54(15):3999-4008. DOI: 10.1017/S0033291724001697In 2015, Usha Gowda and colleagues at Monash University pooled nine trials in people with depression or depressive symptoms. They found no significant improvement from vitamin D. However, most participants had only mild symptoms and adequate vitamin D levels at baseline.
The authors called for studies in people who are both depressed and deficient. What this means for you: the answer depends heavily on who is studied.
Gowda U et al. Nutrition. 2015;31(3):421-429. DOI: 10.1016/j.nut.2014.06.017What follows from this? I measure vitamin D instead of guessing. A proven deficiency deserves to be corrected, for many reasons that go far beyond mood. Why the winter sun in Germany is often not enough for this, I explain in the article Vitamin D deficiency in winter. But I do not see vitamin D as a substitute for the light signal at the eye.
A thought about timing makes the difference tangible. Lambert found the association with the hours of sunshine on the same day. A vitamin D level, by contrast, builds up over weeks. If you feel lighter after a single sunny morning, vitamin D is an unlikely explanation.
Vitamin D is important. But it is not the whole story of the sun.
If you only take the capsule and stay indoors all winter, you may be covering the skin pathway and leaving the eye pathway empty.
And now you know why, when it comes to sun and mood, I ask two separate questions: What is your vitamin D level, and how much daylight does your eye see?
Endorphins from the skin: why sun can feel so good
Do you know the feeling when the first warm spring sun falls on your face? You close your eyes and just want to stay sitting there. Many people describe it as an almost physical pleasure. There is an intriguing, if still preliminary, lead on this too.
In 2014, Gillian Fell and David Fisher at Massachusetts General Hospital showed that mouse skin cells produce beta-endorphin, an endogenous opioid, after low-dose UV radiation. Blood levels rose and pain sensitivity decreased. When the opioid receptors were blocked after prolonged UV exposure, the animals showed signs of withdrawal.
The authors suggest that this mechanism might have promoted sun-seeking in evolution, but today may also contribute to the rise in skin cancer. These are animal data. Whether a similar pathway shapes the human craving for sun has not yet been conclusively clarified.
Fell GL et al. Cell. 2014;157(7):1527-1534. DOI: 10.1016/j.cell.2014.04.032This study shows the double nature of the sun particularly clearly. The same sense of wellbeing that draws us outside can also tempt us to lie in the midday sun for too long. And that is exactly where the risk begins.
The good feeling in the sun is no proof that more sun is always better.
For mood, what you mainly need is light at the eye. For the pleasant feeling on your skin, less is often enough than your body whispers to you in that moment.
And now you know why I see the sun as both a natural force and a dose.
The KPNI view: the sun touches all four systems
In clinical psychoneuroimmunology, KPNI for short, we look at a question through four lenses. With sun and mood, all four interlock, and that is exactly what makes the topic so rich.
Retina, clock, serotonin
Melanopsin cells report brightness to the internal clock. The serotonin system seems to swing along with hours of sunshine and the season.
Melatonin and cortisol
Morning light can suppress melatonin and organize the daily rhythm of cortisol. In the body, vitamin D behaves more like a hormone than a vitamin.
Light as a modulator
Vitamin D can influence inflammatory processes via receptors on immune cells. A stable day-night rhythm also seems to matter for immune balance.
Energy and rhythm
An earlier, more stable rhythm could help organize sleep, appetite and drive. Movement outdoors brings light and activity at the same time.
One thing matters to me here: these four lenses are no proof that the sun improves everything. They are a map showing how many places light can act on your body. How I look at mental health as a whole on several levels, I describe in the article on a holistic approach to depression.
The sun is not a supplement you take in measured doses. It is a rhythm setter for an entire network.
That is exactly why a morning walk can sometimes touch more levels than any single capsule.
And now you know why I never see light as only a mood topic.
Light therapy for seasonal depression: a studied option
What if the winter low is not just a damper, but turns into a genuine depression every year? Then the sun as an everyday tip is no longer enough. Then the topic belongs in the hands of a physician or psychotherapist.
In 2005, Robert Golden and colleagues at the University of North Carolina analyzed randomized trials of light therapy for mood disorders. Bright light in winter depression showed an effect size of 0.84 across eight studies, and dawn simulation an effect size of 0.73 across five studies.
At the same time, only a small proportion of the studies found met the strict quality criteria. What this means for you: light therapy is an option that has been studied for seasonal depression, but its use belongs under medical supervision.
Golden RN et al. Am J Psychiatry. 2005;162(4):656-662. DOI: 10.1176/appi.ajp.162.4.656I deliberately give no instructions here. Whether light therapy is an option for you depends on the diagnosis, your sleep rhythm, your eyes and your medications. Anyone who has bipolar disorder, or knows of it in their family, should only use bright light under psychiatric supervision. More on this, including psychotherapy and medication, can be found in my article on winter depression and lack of light.
Light is not an opponent of medicine. In a genuine depression, it is at most one building block alongside psychotherapy and, if necessary, medication.
And now you know why I take light seriously but never see it as a substitute for a diagnosis.
Sun protection and light: how the two fit together
Perhaps you are thinking now: hold on, the sun is dangerous. That is true as well. The sun is a natural force and a risk at the same time. The good news: once you separate the two pathways, you do not have to choose between mood and skin health.
In 2005, Sara Gandini and colleagues at the European Institute of Oncology in Milan analyzed fifty-seven studies on sun exposure and melanoma. Intermittent, that is sporadic, sun exposure and a history of sunburns emerged as significant risk factors. High, continuous occupational sun exposure, by contrast, was rather inversely associated with melanoma.
What this means for you: not every minute of sun carries the same risk. Sudden, intense doses on unaccustomed skin seem to be especially critical, as on holiday after a long winter.
Gandini S et al. Eur J Cancer. 2005;41(1):45-60. DOI: 10.1016/j.ejca.2004.10.016In 2008, Leslie Dennis and her team at the University of Iowa pooled data from 51 study populations. Melanoma risk rose with every additional burn, at all stages of life, not only in childhood. The risk per five sunburns per decade was highest in adulthood and when viewed over the whole lifetime.
The authors advise avoiding sunburns at every age. What this means for you: the goal is light, not redness.
Dennis LK et al. Ann Epidemiol. 2008;18(8):614-627. DOI: 10.1016/j.annepidem.2008.04.006- Mornings are light at the eye, midday is UV on the skin: In the early hours, UV exposure is low, but the light signal for the internal clock is already relevant.
- No sunburn: The mood pathway through the eye does not need reddened skin. In the midday sun, especially in summer, sun protection is part of the picture.
- Never look directly into the sun: What is meant is bright ambient light, not looking at the sun's disc. That can damage the retina.
- Photosensitizing medications: Some substances, including St John's wort and certain antibiotics, increase the light sensitivity of skin and eyes. Have this checked by a physician.
- Eye conditions: If you have a retinal condition, how to handle bright light should be discussed with an ophthalmologist.
How much sun on the skin may be reasonable depending on skin type and season, I describe in detail in my article How much sun does the body really need?.
Sun protection and the hunger for light are not opponents. One protects your skin, the other nourishes your internal clock.
If you separate the two, you can be outdoors without getting burned.
And now you know why I recommend morning light and still take sunburn seriously.
Three levers for more light in everyday life
You don't have to turn your life upside down. Three small steps may be enough to show your eye more of the day again. They do not replace treatment if you are suffering from depression.
Your three levers
- Morning light outdoors: Try to spend some time outside in the first hour after getting up, for example on your way to work, with your coffee on the balcony or on a short walk around the block. Even a grey sky can give your eye considerably more light than any apartment.
- Think of light and vitamin D separately: Have your vitamin D level measured instead of guessing, and correct a proven deficiency in consultation with your doctor. For your mood, though, do not rely on the capsule alone, but also make sure your eyes get daylight.
- Bright by day, dark in the evening: The brighter your day, the clearer the signal for your internal clock can be. In the evening, by contrast, choose dim, warm light and less screen time. That gives your rhythm a clear contrast.
If you want to go deeper into how light, cold, movement and rhythm can work together in everyday life, read my overview Using natural forces in everyday life. And if your sleep is what suffers most, you will find further connections in the article on sleep and depression.
"The sun writes you two letters. Your skin reads one, your brain reads the other. Read both."
Shukri Jarmoukli, ViveCura BerlinThis is not about a few minutes of light. It is about whether your life in winter feels like nothing more than holding out, or also like living. When you understand how light can speak to your own mind, you regain a piece of self-determination over the dark months. That is freedom.
Frequently asked questions about sun, serotonin and mood
Does the sun really make you happier?
Making you happy is saying too much. What studies show: more time in daylight goes along with better mood. In the UK Biobank, with more than 400,000 adults, every additional hour spent outdoors during the day was associated with fewer episodes of low mood, less anhedonia and more reported happiness. This is an observational study and does not prove cause. It is biologically plausible, however, that light may influence mood through the internal clock and the serotonin system.
How are sunlight and serotonin connected?
A study in The Lancet in 2002 measured a breakdown product of serotonin in 101 healthy men, directly in the blood draining from the brain. Serotonin turnover was lowest in winter and rose with the number of hours of bright sunshine on the day of measurement. A PET study also found more serotonin transporters in the brain in autumn and winter than in summer. Both findings suggest that light might help regulate the serotonin system across the year.
Is mood better in summer because of vitamin D?
Probably only to a smaller extent. Light on the eye and UV radiation on the skin are two different pathways. The mood effect through the eye, the internal clock and serotonin appears quickly, sometimes within a day. Vitamin D builds up over weeks. Large studies on vitamin D supplements show mixed results, and the VITAL-DEP trial with more than 18,000 people found no preventive effect on depression. A measured deficiency still deserves to be corrected.
Can a vitamin D capsule replace sunlight for the mind?
Based on current knowledge, no. A capsule can raise your vitamin D level, but it does not reach the light sensors in the retina that set the internal clock. Meta-analyses find a small effect of vitamin D on depressive symptoms, though with very inconsistent studies and, in part, very low certainty of evidence. Light and vitamin D are therefore two separate building blocks that do not replace each other.
Why do I feel so different in winter than in summer?
In winter, less and weaker light arrives in the morning. The internal clock receives a weaker timing signal, the night hormone melatonin may run longer, and the serotonin system seems to be set differently by season. On top of that comes less movement outdoors and less social activity. People differ in how sensitive they are to light, and genetic data point in the same direction. That is why some people barely notice the change of seasons and others feel it very clearly.
Do I need direct sun on my skin for my mood?
For the light effect through the internal clock, what matters is what reaches your eye, not how much UV your skin gets. Outdoor daylight is usually many times brighter than indoor lighting, even on cloudy days. Spending time outside in the shade or under cloud cover can therefore already be a relevant light signal. You do not need a sunburn for this, and you should never look directly into the sun.
How does sun protection fit with more light for mood?
Well, once you separate the pathways. Part of the skin cancer risk is linked to sunburns. A meta-analysis of 51 study populations found a higher melanoma risk with every additional burn, at every age. For mood, on the other hand, what counts most is light at the eye, especially in the morning, when UV exposure is low. Morning light outdoors and sun protection in the midday sun are therefore not mutually exclusive.
Has light therapy been studied for seasonal depression?
Yes. Light therapy for seasonal depression has been studied in randomized trials. A meta-analysis in the American Journal of Psychiatry in 2005 found an effect size of 0.84 across eight studies for bright light in winter depression, while only a few studies met strict quality criteria. Light therapy is therefore an option that has been studied. Whether it suits you belongs in a conversation with a physician, also with regard to your eyes, medications and a possible bipolar predisposition.
Why does sun on the skin feel so good?
Warmth, relaxation and the holiday feeling certainly play a role. An intriguing study appeared in the journal Cell in 2014: in mice, low-dose UV radiation raised the blood level of beta-endorphin produced by the skin, and after the opioid receptors were blocked, the animals showed signs of withdrawal. These are animal data. Whether a similar mechanism contributes to the human craving for sun has not yet been conclusively clarified.
When should I seek medical help for low mood?
When low mood, lack of drive or loss of joy lasts longer than about two weeks, when work, relationships or sleep suffer noticeably, or when the pattern repeats every year. Light is then no substitute for an assessment by a physician or psychotherapist. If you have thoughts of no longer wanting to live, you can reach the German Telefonseelsorge free of charge around the clock at 0800 111 0 111 and 0800 111 0 222. In acute danger, call the emergency number 112.
Further reading in the ViveCura guide
These articles connect directly to this topic.
Natural forces
Light, cold, warmth, movement, rhythm
You are hereWinter depression
When the dark season weighs on your mood
Morning light
How light sets the internal clock
Sun
Between fear of skin cancer and deficiency
Vitamin D in winter
Why the winter sun is often not enough
Blue light
Evening light, rhythm and sleep
Depression
Several levels of treatment
Sleep and depression
The bidirectional vicious circle
Natural forces in everyday life
Using light, cold and rhythm
Sources
- Lambert GW, Reid C, Kaye DM, Jennings GL, Esler MD. Effect of sunlight and season on serotonin turnover in the brain. Lancet. 2002;360(9348):1840-1842. DOI: 10.1016/s0140-6736(02)11737-5 [Pathophysiology, observational, n=101]
- Praschak-Rieder N, Willeit M, Wilson AA, Houle S, Meyer JH. Seasonal variation in human brain serotonin transporter binding. Arch Gen Psychiatry. 2008;65(9):1072-1078. DOI: 10.1001/archpsyc.65.9.1072 [Pathophysiology, PET study, n=88]
- Hattar S, Liao HW, Takao M, Berson DM, Yau KW. Melanopsin-containing retinal ganglion cells: architecture, projections, and intrinsic photosensitivity. Science. 2002;295(5557):1065-1070. DOI: 10.1126/science.1069609 [In vivo, rat and mouse]
- LeGates TA, Altimus CM, Wang H et al. Aberrant light directly impairs mood and learning through melanopsin-expressing neurons. Nature. 2012;491(7425):594-598. DOI: 10.1038/nature11673 [In vivo, mouse]
- Burns AC, Saxena R, Vetter C, Phillips AJK, Lane JM, Cain SW. Time spent in outdoor light is associated with mood, sleep, and circadian rhythm-related outcomes: A cross-sectional and longitudinal study in over 400,000 UK Biobank participants. J Affect Disord. 2021;295:347-352. DOI: 10.1016/j.jad.2021.08.056 [Real-world, cohort, cross-sectional and longitudinal, n over 400,000]
- Burns AC, Phillips AJK, Rutter MK, Saxena R, Cain SW, Lane JM. Genome-wide gene by environment study of time spent in daylight and chronotype identifies emerging genetic architecture underlying light sensitivity. Sleep. 2023;46(3):zsac287. DOI: 10.1093/sleep/zsac287 [Real-world, genome-wide study, n=280,897]
- Fell GL, Robinson KC, Mao J, Woolf CJ, Fisher DE. Skin β-endorphin mediates addiction to UV light. Cell. 2014;157(7):1527-1534. DOI: 10.1016/j.cell.2014.04.032 [In vivo, mouse]
- Golden RN, Gaynes BN, Ekstrom RD et al. The efficacy of light therapy in the treatment of mood disorders: a review and meta-analysis of the evidence. Am J Psychiatry. 2005;162(4):656-662. DOI: 10.1176/appi.ajp.162.4.656 [Meta-analysis, RCTs]
- Okereke OI, Reynolds CF, Mischoulon D et al. Effect of long-term vitamin D3 supplementation vs placebo on risk of depression or clinically relevant depressive symptoms and on change in mood scores: A randomized clinical trial. JAMA. 2020;324(5):471-480. DOI: 10.1001/jama.2020.10224 [RCT, n=18,353]
- Mikola T, Marx W, Lane MM et al. The effect of vitamin D supplementation on depressive symptoms in adults: A systematic review and meta-analysis of randomized controlled trials. Crit Rev Food Sci Nutr. 2023;63(33):11784-11801. DOI: 10.1080/10408398.2022.2096560 [Meta-analysis, k=41 RCTs, n=53,235]
- Ghaemi S, Zeraattalab-Motlagh S, Jayedi A, Shab-Bidar S. The effect of vitamin D supplementation on depression: a systematic review and dose-response meta-analysis of randomized controlled trials. Psychol Med. 2024;54(15):3999-4008. DOI: 10.1017/S0033291724001697 [Meta-analysis, k=31 RCTs, n=24,189]
- Gowda U, Mutowo MP, Smith BJ, Wluka AE, Renzaho AM. Vitamin D supplementation to reduce depression in adults: meta-analysis of randomized controlled trials. Nutrition. 2015;31(3):421-429. DOI: 10.1016/j.nut.2014.06.017 [Meta-analysis, k=9 RCTs, n=4,923]
- Gandini S, Sera F, Cattaruzza MS et al. Meta-analysis of risk factors for cutaneous melanoma: II. Sun exposure. Eur J Cancer. 2005;41(1):45-60. DOI: 10.1016/j.ejca.2004.10.016 [Meta-analysis, 57 observational studies]
- Dennis LK, Vanbeek MJ, Beane Freeman LE, Smith BJ, Dawson DV, Coughlin JA. Sunburns and risk of cutaneous melanoma: does age matter? A comprehensive meta-analysis. Ann Epidemiol. 2008;18(8):614-627. DOI: 10.1016/j.annepidem.2008.04.006 [Meta-analysis, 51 study populations]