Seasonal Affective Disorder (SAD), as the name suggests, has long been linked to the time of year; namely winter, when the days are short and the rays are in short supply. It seems reasonable to propose, then, that there may be a link between SAD and vitamin D, as sunlight is a direct precursor of vitamin D.
This is exactly the hypothesis recently put forward, formally, by a research team at the University of Georgia, who report their rationale in the journal Medical Hypothesis, under the title 'Possible contributions of skin pigmentation and vitamin D in a polyfactorial model of seasonal affective disorder.'
In it, the authors note that SAD usually begins in Autumn and continues throughout the winter months, with symptoms including anxiety, depression, irritability and feelings of guilt or hopelessness. It is more common, they say, among those who live at high altitudes or in cloudy regions.
Vitamin D levels fluctuate in direct response to available sunlight, with a lead time of about eight weeks from exposure to ultraviolet (UV) radiation. This correlates with the time between peak intensity of ultraviolet (UV) radiation and the initial onset of SAD symptoms, lending credibility to the notion of a direct relationship between SAD and vitamin D.
Author, Michael Kimlin, says that vitamin D is known to play a part in the synthesis of both dopamine and serotonin, low levels of which are associated with depression. Commenting on the research, he says:
"What we know now is that there are strong indications that maintaining adequate levels of vitamin D are also important for good mental health. A few minutes of sunlight exposure each day should be enough for most people to maintain an adequate vitamin D status."That's all well and good for those of us perched somewhere on or near the equator, but what about us poor unfortunates who languish mole-like in solar deprivation during the winter months? Well the first thing to say is, make the most of what you've got; if the sun is shining, get out there and drink it in - even a few minutes is enough to make a valuable contribution, according to the authors of this study.
Failing that, the best source of dietary vitamin D is oily fish - salmon, mackerel, tuna and the like. If you really want to make sure you're getting enough, then, just like my grandmother used to say, a tablespoon of cod liver oil now and again may be the way to go.
With the incidence of depression at such an all-time high, let's not allow any that is obviously treatable to slip through the net. During winter, always rule out SAD.
Written by Jacqui Hogan