Food and Behaviour Research

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

Stewart AE, Roecklein KA, Tanner S, Kimlin MG (2014) Med Hypotheses. 83(5) 517-25 Elsevier Ltd

Web URL: Read more and related articles on PubMed here

Abstract:

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 Dlevels that, especially following their migration to regions of higher latitude, could contribute to the emergence of SAD and other psychiatric and physical health problems.

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Please find the related news item here:

02 December 2014 - Vitamin D deficiency, depression linked in international study