As the daylight decreases over the winter, people will feel a depression that goes away during the spring and summer.
Women are more likely to experience seasonal affective disorder, along with individuals who live furthest from the equator and those who have a close relative who experiences SAD.
Although there isn’t an exact cause for SAD, researchers believe it has something to do with a lack of sunlight. A lack of daylight can upset the biological clock controlling your sleep-wake pattern and affect serotonin, a brain chemical known to affect mood.
Research conducted on mice may give researchers a bigger clue and deeper insight on what affects seasonal affective disorder. The researchers found a small region in the brain of the mice, called the dorsal raphe nucleus, which contains the neurons that control mood – like serotonin. Low levels of serotonin have been shown to be associated with low mood, while high levels reveal a happier mood.
Furthermore, the researchers also found that the month in which the mice were born could affect their risk of developing SAD.
The mice were divided into three groups: The first group was born and raised in a summer-like cycle with 16 hours of sunlight and eight hours of darkness, the next was born and raised in a spring/fall-like cycle with 12 hours of light and 12 hours of dark, and lastly, the third group was born and raised in a winter-like cycle with eight hours of light and 16 hours of darkness.
Mice born and raised in the summer-like cycle had the lowest levels of depressive behavior compared to the spring/fall or winter group. Summertime mice were also found to have the highest serotonin levels.
Even when summertime mice were switched to a winter cycle, their serotonin levels remained high into adulthood.
Researcher Douglas McMahon, Ph.D., said, “This showed that early life seasonal photoperiods can have enduring effects on the serotonin neurons. If such an effect occurs in humans, and is long-lasting, it could contribute to the season of birth modulation of SAD risk.”
Previous research unveiled the same findings to be true in humans; their birth season could be tied with the risk of mood disorders. What the researchers found was that those born in certain seasons had a higher likelihood of developing mood disorders.
Lead researcher, Xenia Gonda, Ph.D., said, “Biochemical studies have shown that the season in which you are born has an influence on certain monoamine neurotransmitters, such as dopamine and serotonin, which is detectable even in adult life. This led us to believe that birth season may have a longer-lasting effect. Our work looked at over 400 subjects and matched their birth season to personality types in later life. Basically, it seems that when you are born may increase or decrease your chance of developing certain mood disorders.
“We can’t yet say anything about the mechanisms involved. What we are now looking at is to see if there are genetic markers which are related to season of birth and mood disorder.”
The researchers uncovered the following trends:
Professor Eduard Vieta, M.D., commented on the research and said, “Seasons affect our mood and behavior. Even the season at our birth may influence our subsequent risk for developing certain medical conditions, including some mental disorders. What’s new from this group of researchers is the influence of season at birth and temperament. Temperaments are not disorders but biologically-driven behavioral and emotional trends. Although both genetic and environmental factors are involved in one’s temperament, now we know that the season at birth plays a role too. And the finding of ‘high mood’ tendency (hyperthymic temperament) for those born in summer is quite intriguing.”
Although seasonal affective disorder is commonly due to a lack of sunshine, which occurs in the winter, there is still a risk of experiencing SAD in the summertime as well. It puzzles many researchers as to why someone would feel depression in the summertime, but they theorize that it could have something to do with too much sun exposure or heat. Allergies, too, have been shown to play a role in summertime depression, and even changes in sleeping habits due to more light can contribute to SAD.
Unfortunately, summertime SAD is not studied as often as winter SAD, so treatment methods are lacking. Doctors must simple treat cases of summertime seasonal affective disorder on a case by case basis.
As mentioned, SAD can be caused by a reduction in sunlight and changes to our circadian rhythm. Signs and symptoms of seasonal affective disorder include:
There are numerous treatments that can help seasonal affective disorder. Treatments for seasonal affective disorder include:
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