Spending time basking in the sun may be more
important than you think. Sure, it's a sensual pleasure and brightens your day.
But far beyond that, the summer sun may help you avoid winter depression.
Called seasonal affective disorder (SAD), seasonal
depression and mood variation is known to be related to how much sunlight you
receive. Now some researchers are concluding that greater exposure to summer
sun may help reduce mood problems during the winter months that follow.
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Your mood is influenced by a complex web of relationships
between sunlight, melatonin (the sleep hormone) and serotonin (the hormone
associated with wakefulness and elevated mood). As darkness falls, your
melatonin levels naturally increase. And as the morning light emerges,
melatonin levels decrease.
Serotonin levels increase when you're exposed to bright
light -- a major reason why moods tend to be more elevated during the summer.
This hormone is the basis of today's most popular and successful antidepressant
drugs, called selective serotonin re-uptake inhibitors (SSRIs). These drugs
work by helping naturally produced serotonin stay in the bloodstream longer,
keeping your mood and energy levels higher.
Light Therapy: Better Than SSRIs?
It is well known that bright-light therapy can bring quick
benefits to people with depression or SAD, because light affects the
melatonin-serotonin system and elevates mood.
In fact, some researchers are concluding that light therapy
may help to alleviate SAD symptoms faster than antidepressant drugs. In a
recent review of clinical trials of light therapy, Dr. Daniel Kripke and his
colleagues at the Circadian Pacemaker Laboratory at the University of
California, San Diego reported that light therapy benefits not only SAD
patients but also people suffering from other forms of depression.
The study, published in the Journal of Affective Disorders,
also concluded that patients who undergo both light and drug therapy could get
the greatest benefits because the two therapies may enhance each other.
The Summer-Winter Connection
However, few doctors have considered the possibility that
sunlight exposure in the summer could impact how you feel months later. This is
the subject of research by Dr. Timo Partonen and his colleagues at the
University of Helsinki's National Public Health Institute in Finland.
The critical link seems to be the relationship between
summer light and winter levels of vitamin D. Light stimulates the production of
cholecalciferol, which the body eventually transforms into vitamin D. The
vitamin then helps the body maintain higher levels of serotonin during the
Partonen's team has found that blood levels of
cholecalciferol naturally peak in the fall months. So getting more exposure to
sunlight during the summer may help you build up a store of cholecalciferol
that lasts through the fall. All this cholecalciferol apparently spurs your
body to produce more vitamin D during the darker winter months, which leads to
higher serotonin levels.
Partonen contends that the amount of serotonin you have in
the winter is determined by your exposure to light the previous summer -- and
that soaking up more sunlight in the summer will increase your chances of
preventing or reducing depression during the winter.