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Serotonin related to season, light and perhaps latitude and vitamin D

See also VitaminDWiki


See on the web

  • VitaminDCouncil new and working as of June 2011
    • “Low vitamin D levels may be related to depression rather than contributing to the disorder.”
    • “Women in Washington State increased their vitamin D levels to 47 ng/mL by taking 5000 IU of vitamin D each day during the winter. In some of these women, their depressive symptoms lessened as indicated by the decrease in their scores on a depression test.”
    • Overweight and obese Norwegian women took 20,000 or 40,000 IU per week of vitamin D and their symptoms of depression decreased. Their scores were also lower on a depression test.

Clips from WikiPedia SAD

  • Although experts were initially skeptical, this condition is now recognized as a common disorder, with its
       prevalence in the U.S. ranging from 1.4 percent in Florida to 9.7 percent in New Hampshire.
  • Subsyndromal Seasonal Affective Disorder is a milder form of SAD experienced by an estimated 14.3% (vs. 6.1% SAD) of the U.S. population.
  • Icelandic people have low levels of SAD, but eat 225 lb of fish per person per year as opposed to about 50 lb in the US and Canada (Fish is high in vitamin D)

Possible contributions of skin pigmentation and vitamin D in a polyfactorial model of seasonal affective disorder - 2014

Medical Hypotheses, Volume 83, Issue 5, November 2014, Pages 517–525
Alan E. Stewarta, , , Kathryn A. Roeckleinb, Susan Tannera, Michael G. Kimlinc

Seasonal affective disorder (SAD) is a polyfactorial and polygenetic disorder that involves biological and psychological sub-mechanisms that differentially involve depression, seasonality, circadian rhythms, retinal sensitivity, iris pigmentation, sleep factors, and the neurotransmitters involved with these systems. Within the framework of the polyfactorial conceptualization of SAD, we review the possible contributions of vitamin D3 with respect to the aforementioned sub-mechanisms. We hypothesize that rather than functioning primarily as a proximal or direct sub-mechanism in the etiology of SAD, vitamin D likely functions in a more foundational and regulative role in potentiating the sub-mechanisms associated with the depressive and seasonality factors.
There are several reasons for this position:

  • 1. vitamin D levels fluctuate in the body seasonally, with a lag, in direct relation to seasonally-available sunlight;
  • 2. lower vitamin D levels have been observed in depressed patients (as well as in patients with other psychiatric disorders) compared to controls;
  • 3. vitamin D levels in the central nervous system affect the production of both serotonin and dopamine; and
  • 4. vitamin D and vitamin D responsive elements are found throughout the midbrain regions and are especially concentrated in the hypothalamus, a region that encompasses the circadian timing systems and much of its neural circuitry.

We also consider the variable of skin pigmentation as this may affect levels of vitamin D in the body. We hypothesize that people with darker skin pigmentation may experience greater risks for lower vitamin D levels that, especially following their migration to regions of higher latitude, could contribute to the emergence of SAD and other psychiatric and physical health problems.

Publisher wants $32 for the PDF


Light therapy as a treatment for epilepsy. - 2011

Med Hypotheses. 2011 May;76(5):661-4. Epub 2011 Feb 18.
Baxendale SA.
Department of Clinical and Experimental Epilepsy, Institute of Neurology UCL, Queen Square, London, UK. sallieb at ion.ucl.ac.uk

From a neurobiological level to epidemiological studies, there are four strands of evidence in the scientific literature that indicate that light therapy could be an effective treatment for some people with epilepsy.

  • (1) Sunlight is important in the endogenous production and regulation of melatonin and vitamin D, both of which influence seizure thresholds. Although melatonin influences seizure thresholds, the relationship is complex. General down-regulating effects may have different effects on seizure thresholds for people with generalised and partial epilepsy syndromes. Specific actions within the hippocampus may mean that patients with temporal lobe epilepsy are particularly susceptible to the endogenous expression of melatonin via inhibitory actions on dopaminergic activity reducing seizure thresholds.
  • (2) If suppression of melatonin results in fewer seizures this should be evident in seasonal variations in seizure frequencies. Seizure frequencies increase in the winter and on dull overcast days. Within this larger circannual rhythm, local light conditions are also associated with variations in seizure frequencies. Controlling for seasonal patterns, complex partial seizures are significantly less likely to occur on bright sunny days, than on dull days with fewer hours of sunshine, regardless of the time of year.
  • (3) On a wider scale, some epidemiological studies also suggest a lower prevalence of epilepsy in southern Europe compared to Scandinavia and Northern Europe.
  • (4) Light therapy is an established medical treatment for depression. Recent research suggests that some forms of epilepsy and depression are bi-directional conditions. The mechanism of action underlying light therapy for affective disorders remains the subject of much research but is thought to involve the enhancement of the monoaminergic systems targeted by antidepressant drugs (serotonin, dopamine, and norepinephrine); systems also implicated in a number of epilepsy syndromes.


In this paper, we propose the hypothesis that exposure to high intensity light may be an effective, non-invasive add-on treatment for people with temporal lobe epilepsy. Although it is more likely to be palliative than curative, it may help smooth out some of the seasonal peaks in seizure frequencies, a pattern that increases the risk of serious manifestations of the condition such as status epilepticus and sudden unexpected death in epilepsy.

Copyright © 2011 Elsevier Ltd. All rights reserved. PMID: 21333455
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Effect of sunlight exposure on cognitive function among depressed and non-depressed participants: a REGARDS cross-sectional study.- 2009

Environ Health. 2009 Jul 28;8:34.
Kent ST, McClure LA, Crosson WL, Arnett DK, Wadley VG, Sathiakumar N.
Department of Epidemiology, School of Public Health, University of Alabama at Birmingham, Alabama, USA. shia at uab.edu

BACKGROUND: Possible physiological causes for the effect of sunlight on mood are through the suprachiasmatic nuclei and evidenced by serotonin and melatonin regulation and its associations with depression. Cognitive function involved in these same pathways may potentially be affected by sunlight exposure. We evaluated whether the amount of sunlight exposure (i.e. insolation) affects cognitive function and examined the effect of season on this relationship.
METHODS: We obtained insolation data for residential regions of 16,800 participants from a national cohort study of blacks and whites, aged 45+. Cognitive impairment was assessed using a validated six-item screener questionnaire and depression status was assessed using the Center for Epidemiologic Studies Depression Scale. Logistic regression was used to find whether same-day or two-week average sunlight exposure was related to cognitive function and whether this relationship differed by depression status.
RESULTS: Among depressed participants, a dose-response relationship was found between sunlight exposure and cognitive function, with lower levels of sunlight associated with impaired cognitive status (odds ratio = 2.58; 95% CI 1.43-6.69). While both season and sunlight were correlated with cognitive function, a significant relation remained between each of them and cognitive impairment after controlling for their joint effects.
CONCLUSION: The study found an association between decreased exposure to sunlight and increased probability of cognitive impairment using a novel data source. We are the first to examine the effects of two-week exposure to sunlight on cognition, as well as the first to look at sunlight's effects on cognition in a large cohort study.

PMID: 19638195 CLICK HERE for PDF
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Seasonal variation in human brain serotonin transporter binding.- 2008

Arch Gen Psychiatry. 2008 Sep;65(9):1072-8.
Praschak-Rieder N, Willeit M, Wilson AA, Houle S, Meyer JH.
Vivian M. Rakoff PET Imaging Centre, Centre for Addiction and Mental Health, 250 College St, Toronto, ON M5T 1R8, Canada.

CONTEXT: It is a common experience in temperate zones that individuals feel happier and more energetic on bright and sunny days and many experience a decline in mood and energy during the dark winter season. Brain serotonin is involved in the regulation of physiologic functions, such as mating, feeding, energy balance, and sleep. Although these behaviors and serotonin-related conditions show a clear seasonal pattern in humans, the molecular background of seasonal changes in serotonin function is entirely unknown. The serotonin transporter is a key element in regulating intensity and spread of the serotonin signal.
OBJECTIVES: To detect seasonal variations in serotonin transporter binding in the living human brain and to detect correlations between serotonin transporter binding and duration of daily sunshine.
DESIGN: Regional serotonin transporter binding potential values, an index of serotonin transporter density, were assessed from December 1, 1999, to December 9, 2003, in a consecutive sample of healthy volunteers. Binding potential values were related to meteorologic data.
SETTING: Tertiary care psychiatric hospital.
PARTICIPANTS: Volunteer sample of 88 drug-naive healthy individuals.
INTERVENTION: Carbon 11-labeled 3-amino-4-(2-dimethylaminomethyl-phenylsulfanyl)-benzonitrile positron emission tomography.
MAIN OUTCOME MEASURE: Regional serotonin transporter binding potential values.
RESULTS: Serotonin transporter binding potential values were significantly higher in all investigated brain regions in individuals investigated in the fall and winter compared with those investigated in the spring and summer (P = .01 to .001).
Moreover, binding potential values showed negative correlations with average duration of daily sunshine in all brain regions (rho = -0.21 to -0.39; P = .05 to <.001), such that higher values occurred at times of lesser light.
CONCLUSIONS: Serotonin transporter binding potential values vary throughout the year with the seasons. Since higher serotonin transporter density is associated with lower synaptic serotonin levels, regulation of serotonin transporter density by season is a previously undescribed physiologic mechanism that has the potential to explain seasonal changes in normal and pathologic behaviors.
PMID: 18762593

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