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.
A Delicate Balance
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 winter.
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.
What You Can Do
Next winter doesn't have to be all gloom. It depends on what you do this summer. While simply slathering on the sunscreen and heading outdoors may be fine, try the following strategies to take best advantage of the summer sun:
- Dose up: Get up and out early to enjoy the added hours of morning sunlight. These are also the hours in which the risk of sunburn is lowest. (Avoid dozing during the midday sun.)
- Ritual: Practice some form of ritual, meditation, or exercise outdoors for at least 20 minutes each morning. One practice is to face the sun and imagine you are inhaling its light with each in-breath, and that the light is being absorbed throughout your body.
- Sun breaks: During your workday, spend coffee breaks or lunch breaks outdoors to increase your exposure each day.