DNC News


Light and Dark: Ruminations on Vitamin D and Melatonin


Subject: Suicide rates increase with increasing sunlight, while Seasonal Affective Disorder (SAD) is worsened by decreasing light. Are changes in melatonin or Vitamin D production the mediating factor?


  Dawn comes a little earlier each morning and sunset a bit later each evening now that we've made it to the New Year. We've clearly passed the winter Solstice and our hours of daylight will increase until June 21, the longest day of the year.


This change in light has me pondering the effect of light and dark on our lives. Darkness and light like literary themes form the backdrop of our lives yet we hardly pay them mind.


As the days lengthen I ponder their effect on the human psyche. I've written before and called this period from now until mid June, “Suicide Season” because suicide rates will progressively increase with the lengthening of day light hours.


Checking for updates in the scientific literature, I find that there is a new more comprehensive study confirming the earlier ones. In a 2002 article in Epidemiology, Dr. E. Petridou and his colleagues in Athens carefully evaluated statistics from 20 different countries and confirmed the earlier studies. Suicide rates follow a seasonal pattern peaking in the months of maximum daylight, May and June in the northern hemisphere and November and December in the southern. In addition they were able to show statistically that the sunnier a country is, the higher the suicide rates. [i]


This of course goes against everything we would intuitively predict doesn't it? I would have guessed that the darker and gloomier the weather the higher the suicide rates would be. I would have picked a cloudy and damp December in Oregon as more apt to push someone over the edge than a sunny June in Colorado .


Although there is plenty of information supporting these findings, there is no theory to explain it. Petridou suggests that melatonin may play a role as it is the hormone most affected by light and dark but offers neither evidence nor convincing argument to support the idea.


There is a popular belief that sitting under bright lights in the winter is good for one's mood. Seasonal Affective Disorder (SAD), that is the depressive episodes that some people suffer during the autumn, is blamed on lack of sunlight and has become a common complaint in the public's mind. Look at the advertisements for full spectrum lights in every magazine banking on the idea that light will improve the buyer's mood.


Do lights really help SAD people? Although many articles suggest using light therapy to treat SAD, [ii] a review of the evidence in published in 2001 was unable to support the hypothesis. [iii] Light therapy may not help SAD. A 1999 study appears to have figured out the problem; it's that vitamin D stuff again. As summer fades into fall, vitamin D levels stored in the body drop. It is now thought that this decrease of vitamin D causes the drop in mood we call SAD. Treating SAD sufferers with Vitamin D brings relief from symptoms while light therapy provides little or no benefit. [iv] [v]


Light therapy may or may not be effective, but is it safe? Could light therapy trigger the same suicide response as sunlight does? A group in British Columbia looked at this and found that light therapy increased suicidal ideation in about 3% of the people in their study group. Their conclusion was that this was a low number, in their study just 6 people out of 191, and not of concern. Yet when you add up all of the lights being sold for SAD self treatment, 3% may be cause for worry.


An older SAD study from 1989 mentions a hormone called Soltriol and describes it as a sun induced hormone. [vi] I hadn't heard the term before but other studies use the term Soltriol interchangeably with vitamin D-3. It appears that Soltriol or vitamin D-3 regulates many of the seasonal biorhythms of the body in profound ways. [vii] A quote from a 1988 study, “……actions of soltriol involve effects on autonomic and endocrine regulation with changes in tissue and blood hormone levels, innervation of skeletal muscle, immune and stress response, digestion, blood formation, fertility, pregnancy and lactation, general energy metabolism, mental processes and mood, and others,” [viii] suggests how widespread the influence of vitamin D-3 is.


If vitamin D or Soltriol is the messenger of sunlight to the body then perhaps we can describe melatonin as the messenger of darkness. Melatonin production is stimulated by the absence of light and suppressed by the presence of light. Vitamin D is produced in sunlight and not in the dark. Maybe it is the interplay and balance between these two hormones that is important. [ix] Melatonin has been used to treat SAD and appears to improve sleep and energy levels in SAD sufferers. [x] I've written at length about both Vitamin D-3 and melatonin in prior letters especially their role in cancer prevention and treatment.


We always seem to desire a balance of light and dark in our literature and art, perhaps there is an equal need to balance Soltriol and melatonin in our body chemistry. Such basic themes of life and we barely understand them.


  I've never thought of Vitamin D as being time dependent in a circadian manner; rather I've thought of it as something made and then stored in the body. Levels vary by the season not by the day. Melatonin is the opposite. It is made and rapidly metabolized so that levels fluctuate rapidly between night and day. What melatonin does for calibrating our daily circadian biorhythms, Soltriol apparently does for our seasonal rhythms. Perhaps there may be more to this. Could the timing of Vitamin D production also play a role in daily circadian rhythms? Does it matter what time of day one takes a Vitamin D? At this point we have no idea.


None of this offers me a decent explanation for why sunlight triggers suicides. What sort of evolutionary advantage can we hypothesize that would suggest a survival advantage that would favor suicidal ideation triggered by light? Perhaps suicide is the extreme behavior that shows up statistically. Maybe sunlight also triggers an increase in other impulsive but less dangerous behaviors which provide survival advantage for the individual or species that offsets the life's lost. If we were migratory hunter gatherers once upon a time, might there be an advantage to feeling dissatisfied in the spring and wanting to split town and head out for somewhere new? Even with my famed BS degree, I am not going to go further than this. Perhaps as time goes on more information will come to light that will make sense of this. At the moment I'm in the dark.


With all these thoughts in mind I recall the Rotunda at the American Medical Center located just north of Casa Bonita over in Lakewood . This facility opened a century ago as a Tuberculosis Hospital . The Rotunda was a dome shaped hospital ward with the beds arranged in a circle around the outer perimeter. During the day individual doors were opened and the beds rolled straight out onto a verandah so the patients could lay in the sunlight. Sunlight as medicine…….


The themes of light and dark which run through our literature may be simply reflections of our own internal chemistry. Does thinking of one or the other stimulate some resonant response in our internal chemistry? Is there some reason that we seek to balance the two in our stories that reflects some internal biological imperative?


We know that both Vitamin D and melatonin play important roles in cancer prevention. Is there a ratio or balance between the two that will increase their effect synergistically?


This newsletter brings up far more questions than it answers, but at least we can say one thing for sure;

If you find yourself contemplating suicide this spring, don't take yourself seriously, it's just some biological/hormonal thing which will likely go away by summer time. If desperate, a vacation in the southern hemisphere, say New Zealand , where the days are getting shorter, might be what you need.



A version of this article is posted on our website including abstracts of the studies referenced and links to the other newsletters mentioned.


See the news heading at www.DenverNaturopathic.com

Related articles:

Vitamin D

Vitamin D and Cancer

Vitamin D, Multiple Sclerosis and Rheumatoid Arthritis

Vitamin D prevents falling in the Elderly

Vitamin D and Cardiovascular Disease

Vitamin D and migraines, PCOS, back pain, and Seasonal Affective Disorder

Vitamin D and Diabetes

Vitamin D Testing and Dosing: how to interpet lab tests

Vitamin D Summary: conditions, testing and dosing


Interesting website:  The Vitamin D Council


Melatonin:  It looks like I've forgotten to post some of our past newsletters on Melatonin.  I'll put this on my to do list.  Here is one that is on our website:

Light and Dark exposure changes cancer risks








[i] Epidemiology. 2002 Jan;13(1):106-9.

Comment in:

Epidemiology. 2002 Jul;13(4):492-3; author reply 493-4.

A role of sunshine in the triggering of suicide.

Petridou E, Papadopoulos FC, Frangakis CE, Skalkidou A, Trichopoulos D.


Department of Hygiene and Epidemiology, Athens University Medical School , Greece .


Several reports indicate that suicide follows a seasonal pattern with a dominant peak during the month of maximum daylight. The purpose of this study was to evaluate the hypothesis that sunshine exposure may trigger suicidal behavior. We found a remarkably consistent pattern of seasonality with peak incidence around June in the northern hemisphere and December in the southern hemisphere. Moreover, there was a positive association between the seasonal amplitude of suicide (measured by relative risk) and total sunshine in the corresponding country. These findings indicate that sunshine may have a triggering effect on suicide, and suggests further research in the field of sunshine-regulated hormones, particularly melatonin.

PMID: 11805594 [PubMed - indexed for MEDLINE



[ii] Chronobiol Int. 2003 Mar;20(2):189-207.

Seasonal affective disorder: an overview.

Magnusson A, Boivin D.


Department of Psychiatry, Ullevaal University Hospital , Oslo , Norway . andres.magnusson@psykiatri.uio.no


Seasonal Affective Disorder (SAD) is a condition of regularly occurring depressions in winter with a remission the following spring or summer. In addition to depressed mood, the patients tend to experience increased appetite and an increased duration of sleep during the winter. SAD is a relatively common condition, affecting 1-3% of adults in temperate climates, and it is more prevalent in women. The pathological mechanisms underlying SAD are incompletely understood. Certain neurotransmitters have been implicated; a dysfunction in the serotonin system in particular has been demonstrated by a variety of approaches. The role of circadian rhythms in SAD needs to be clarified. The phase-delay hypothesis holds that SAD patients' circadian rhythms are delayed relative to the sleep/wake or rest/activity cycle. This hypothesis predicts that the symptoms of SAD will improve if the circadian rhythms can be phase-advanced. There is some experimental support for this. SAD can be treated successfully with light therapy. In classical light therapy, the SAD sufferer sits in front of a light box, exposed to 2000-10,000 lux for 30-120 min daily during the winter. Other forms of light treatments, pharmacotherapy, and other therapies are currently being tested for SAD.


Publication Types:



PMID: 12723880 [PubMed - indexed for MEDLINE]



[iii] Psychol Med. 2001 Aug;31(6):949-64.

Full-spectrum fluorescent lighting: a review of its effects on physiology and health.

McColl SL, Veitch JA.


Department of Psychology, McGill University , Montreal , Canada .


BACKGROUND: Full-spectrum fluorescent lighting (FSFL) has been credited with causing dramatic beneficial effects on a wide variety of behaviours, mental health outcomes and physical health effects, as compared to other fluorescent lamp types. These effects are hypothesized to occur because of similarity between FSFL emissions and daylight, which is said to have evolutionary superiority over other light sources. METHOD: This review, covering the period 1941-1999, critically considers the evidence for direct effects of FSFL through skin absorption as well as indirect effects on hormonal and neural processes. CONCLUSIONS: Overall, the evidence does not show dramatic effects of fluorescent lamp type on behaviour or health, neither does it support the evolutionary hypothesis.


Publication Types:


Review, Tutorial

PMID: 11513381 [PubMed - indexed for MEDLINE]



[iv] J Nutr Health Aging. 1999;3(1):5-7.

Vitamin D vs broad spectrum phototherapy in the treatment of seasonal affective disorder.

Gloth FM 3rd, Alam W, Hollis B.


The Department of Medicine, The Union Memorial Hospital , Baltimore , Maryland 21218-2895 , USA .


Seasonal Affective Disorder (SAD) is prevalent when vitamin D stores are typically low. Broad-spectrum light therapy includes wavelengths between 280-320 nm which allow the skin to produce vitamin D. This study was designed to test the hypothesis that vitamin D deficiency might play a role in SAD. A prospective, randomized controlled trial was conducted in a group of 15 subjects with SAD. Eight subjects received 100,000 I.U. of vitamin D and seven subjects received phototherapy. At the onset of treatment and after 1 month of therapy subjects were administered the Hamilton Depression scale, the SIGH-SAD, and the SAD-8 depression scale. All subjects also had serum levels of 25-hydroxyvitamin D (25-OH D) measured before and 1 week after intervention therapy. All subjects receiving vitamin D improved in all outcome measures. The phototherapy group showed no significant change in depression scale measures. Vitamin D status improved in both groups (74% vitamin D group, p < 0.005 and 36% phototherapy group, p < 0.01). Improvement in 25-OH D was significantly associated with improvement in depression scale scores (r2=0.26; p=0.05). Vitamin D may be an important treatment for SAD. Further studies will be necessary to confirm these findings.


Publication Types:

Clinical Trial

Randomized Controlled Trial

PMID: 10888476 [PubMed - indexed for MEDLINE]



[v] Psychopharmacology (Berl). 1998 Feb;135(4):319-23.

Vitamin D3 enhances mood in healthy subjects during winter.

Lansdowne AT, Provost SC.


Department of Psychology, The University of Newcastle , Callaghan NSW, Australia .


Mood changes synchronised to the seasons exist on a continuum between individuals, with anxiety and depression increasing during the winter months. An extreme form of seasonality is manifested as the clinical syndrome of seasonal affective disorder (SAD) with carbohydrate craving, hypersomnia, lethargy, and changes in circadian rhythms also evident. It has been suggested that seasonality and the symptoms of SAD may be due to changing levels of vitamin D3, the hormone of sunlight, leading to changes in brain serotonin. Forty-four healthy subjects were given 400 IU, 800 IU, or no vitamin D3 for 5 days during late winter in a random double-blind study. Results on a self-report measure showed that vitamin D3 significantly enhanced positive affect and there was some evidence of a reduction in negative affect. Results are discussed in terms of their implications for seasonality, SAD, serotonin, food preference, sleep, and circadian rhythms.


Publication Types:

Clinical Trial

Randomized Controlled Trial


PMID: 9539254 [PubMed - indexed for MEDLINE]


[vi] Psychopharmacology (Berl). 1989;97(3):285-94.

Light, vitamin D and psychiatry. Role of 1,25 dihydroxyvitamin D3 (soltriol) in etiology and therapy of seasonal affective disorder and other mental processes.

Stumpf WE, Privette TH.


Department of Cell Biology and Anatomy, University of North Carolina , Chapel Hill 27599.


This is a review and a prospectus of effects of vitamin D on the brain. Effects of sunlight and equivalent artificial light on physiological and behavioral processes are probably mediated, in large part, through the skin-vitamin D-endocrine system. Experimental evidence from our laboratory reveals sites of action and concomitant direct effects of 1,25(OH)2 vitamin D3 (soltriol) on brain, spinal cord, pituitary and other endocrine tissues. This appears relevant for the activation and modulation of mental and endocrine processes, particularly related to seasonal and daily biorhythms. Effects of sunlight and corresponding artificial light are likely to be mediated through direct actions of soltriol on brain and endocrine tissues that are independent of its effect on calcium levels. Those direct actions are receptor mediated and appear to be dose related as they depend on intensity of light and length of exposure, considering light (photons) as a drug. A role for soltriol, the steroid hormone of sunlight, in the etiology and helio- or phototherapy of affective disorders with cyclic seasonal onset (seasonal affective disorder) is discussed and the significance of research in the new frontier of vitamin D and brain relationships is noted.


Publication Types:


Review, Tutorial


PMID: 2497477 [PubMed - indexed for MEDLINE]





[vii] J Steroid Biochem Mol Biol. 1991 Aug;39(2):283-9.

The steroid hormone of sunlight soltriol (vitamin D) as a seasonal regulator of biological activities and photoperiodic rhythms.

Stumpf WE, Privette TH.


Brain Development Research Center , University of North Carolina , Chapel Hill 27599-7090.


Neural and systemic somatotrophic effects of the ultraviolet component of sunlight through the skin-vitamin D endocrine system are considered as alternate or additional to the neuroendocrine effects of the visual component of light through the retino-diencephalic input. The extensive distribution of soltriol nuclear receptor cells, revealed by autoradiography with tritium-labeled 1,25 dihydroxycholecalciferol (vitamin D, soltriol) and related effects, indicate an involvement of vitamin D-soltriol in the actinic induction of seasonal biorhythms. This is considered to be independent of the traditionally assigned effects of vitamin D on systemic calcium regulation. Skin-soltriol mediated seasonal, and to a degree daily, genomic activation involves many target regions in the brain. These include neurons in the central nucleus of the amygdala, in the linked part of the bed nucleus of the stria terminalis, in periventricular hypothalamic neurons, dorsal raphe nucleus, reticular thalamic nucleus and autonomic, endocrine as well as sensory and motor components of the brainstem and spinal cord. Additional to the eye-regulated "suprachiasmatic clock", existence of a soltriol-vitamin D regulated neural "timing circuit(s)" is proposed. Both, activational and organizational effects of soltriol on mature and developing brain regions, respectively are likely to play a role in the regulation of neuronal functions that include the modulation and entrainment of biorhythms. Soltriol's central effects correlate with peripheral effects on elements in skin, bone, teeth, kidney, intestine, heart and blood vessels, endocrine organs, and tissues of the immune and reproductive system.


Publication Types:


Review, Tutorial


PMID: 1888689 [PubMed - indexed for MEDLINE]


[viii] Histochemistry. 1988;89(3):209-19.

Vitamin D--soltriol the heliogenic steroid hormone: somatotrophic activator and modulator. Discoveries from histochemical studies lead to new concepts.

Stumpf WE.


Department of Cell Biology and Anatomy, University of North Carolina , Chapel Hill 27599.


Evidence from autoradiographic studies with 3H 1,25(OH)2 vitamin D3 (soltriol) about its many sites of nuclear binding and multiple actions suggests that the traditional view of "vitamin D and calcium" is too limited and requires modification. A new concept has been developed which proposes that the skin-derived hormone of sunshine, soltriol, is a somatotrophic activator and modulator that affects all vital systems. Regulation of calcium homeostasis is only one of its many actions. Target tissues for soltriol include not only bone, intestine and kidney, but also brain, spinal cord, pituitary, thyroid, endocrine pancreas, adrenal medulla, enteroendocrine cells, thymus, and male and female reproductive organs. Accordingly, actions of soltriol involve effects on autonomic and endocrine regulation with changes in tissue and blood hormone levels, innervation of skeletal muscle, immune and stress response, digestion, blood formation, fertility, pregnancy and lactation, general energy metabolism, mental processes and mood, and others. The skin-mediated transduction of short-wave sunlight induces a purposeful modulation of growth, reproduction and other biological activities in tune with the conditions of the sun cycle and season. Synthesis and actions of vitamin D3-soltriol are dependent not only on the amount of sunlight, but also on the availability of precursor in the skin and access of sunlight, the rate of hydroxylation in liver and kidney, and the modulation of these events by the endocrine status, in particular growth and reproduction. A concept of a five-level control of soltriol synthesis is proposed, in which the hydroxylation steps provide for a sensitive tuning. Relationships between the heliogenic skin-derived hormonal system and the helioprivic pineal-derived hormonal system are recognized and a comprehensive concept of the "endocrinology of sunlight and darkness" is pointed out.


Publication Types:


Review, Tutorial


PMID: 3042715 [PubMed - indexed for MEDLINE]




[ix] Naturwissenschaften. 1988 May;75(5):247-51.

The endocrinology of sunlight and darkness. Complementary roles of vitamin D and pineal hormones.

Stumpf WE.


Department of Cell Biology and Anatomy, University of North Carolina Medical School , Chapel Hill 27599.


Information from autoradiographic studies and follow-up indicates that 1,25(OH)2 vitamin D3 (soltriol) is a somatotrophic activator and modulator, regulated by the amount of sunshine and the endocrine status of the individual, with the purpose of promoting development, reproduction, and maintenance of life. Regulation of calcium homeostasis is only one of its many functions. A close link to the pineal hormone system is apparent. Evidence supports the new concept that the skin-derived hormone of sunlight and the pineal hormone(s) of darkness are messengers with comprehensive actions on endocrine, autonomic, sensory, skeletal, and motor functions. In a complementary fashion, both hormone systems appear to correlate biological activities with the daily and seasonal changes of our solar environment.


Publication Types:


Review, Tutorial


PMID: 3043234 [PubMed - indexed for MEDLINE]


[x] Eur Neuropsychopharmacol. 2003 May;13(3):137-45.

Effect of controlled-release melatonin on sleep quality, mood, and quality of life in subjects with seasonal or weather-associated changes in mood and behaviour.

Leppamaki S, Partonen T, Vakkuri O, Lonnqvist J, Partinen M, Laudon M.


Department of Mental Health and Alcohol Research, National Public Health Institute, Mannerheimintie 166, FIN-00300 Helsinki , Finland . sami.leppamaki@ktl.fi


This study aimed to explore the effects of melatonin on sleep, waking up and well being in subjects with varying degrees of seasonal or weather-associated changes in mood and behaviour. Fifty-eight healthy adults exhibiting subsyndromal seasonal affective disorder (s-SAD) and/or the negative or positive type of weather-associated syndrome (WAS) were randomised to either 2 mg of sustained-release melatonin or placebo tablets 1-2 h before a desired bedtime for 3 weeks. Outcome measures were changes from baseline in sleep quality, sleepiness after waking, atypical depressive symptoms and health-related quality of life by week three. Early morning salivary melatonin concentrations were measured at baseline and treatment cessation in all subjects. Melatonin administration significantly improved the quality of sleep (P=0.03) and vitality (P=0.02) in the subjects with s-SAD, but attenuated the improvement of atypical symptoms and physical parameters of quality of life compared to placebo in the subjects with WAS, positive type.


Publication Types:

Clinical Trial

Randomized Controlled Trial


PMID: 12729938 [PubMed - indexed for MEDLINE]



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