New study explains why some people get sad during the winter season

Monday, October 27, 2014, 10:05 AM - It happens every year—winter arrives and many suffer from seasonal affective disorder (SAD).

Now scientists are a step closer to understanding why some people are more prone to suffering from the affliction than others. The answer lies in a protein called SERT.

SERT or the serotonin transporter is the protein responsible of "ending" the effect of serotonin—thought to be a contributor to feeling happy—and recycles it so it can be used again by the body.

In people prone to the "winter blues," the serotonin transporters are highly active during the winter nights, decreasing serotonin levels. This was determined by using positron emission tomographies in 11 people with SAD and 23 healthy volunteers for comparison.

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The lead researcher Dr. Brenda McMahon will present their findings at a conference later this week.

"The serotonin transporter carries serotonin back into the nerve cells where it is not active so the higher the SERT activity, the lower the activity of serotonin," McMahon told BBC news. "Sunlight keeps this setting naturally low, but when the nights grow longer during the autumn the SERT levels increase resulting in diminishing active serotonin levels."

According to the Canadian Mental Health Association, about two to three per cent of Canadians will experience SAD during their lifetime with adult women being among the most vulnerable.

Some treatments include light therapy, medication, counselling and self-help—such as exercise, a healthy diet, good sleep and reaching out to friends and family.

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