It’s that time of year again — the days are getting shorter, colder, and increasingly blustery. While some revel in the trees changing colours and the prevalence of pumpkin spice-flavoured beverages, others start to feel sad and tired. This change in mood is especially a concern for students — the combined stressors of exams, applications, and bad weather can take a serious toll on mental health during the gloomy winter months.
Seasonal Affective Disorder (SAD) affects one to six per cent of Canadians and is a subtype of major depressive disorder. In addition, 25 per cent of healthy individuals experience seasonal changes in mood, appetite, and sleep that affect their ability to function.
As the name suggests, SAD is a condition where the time of year is correlated with bouts of depression. It typically manifests in the fall and early winter with recovery in the springtime. Symptoms include depressed mood, lack of energy, low motivation, and disturbed sleep patterns.
As there is little ongoing investigation into the neurochemistry of SAD, there is a critical need for research to help better prevention and treatment of seasonal depressive episodes.
There is substantial evidence to suggest that low levels of serotonin, a brain chemical that helps maintain a healthy mood, are involved in the development and maintenance of winter depression.
In 2008, at the Centre for Addiction and Mental Health, Dr. Jeffrey Meyer and his research group discovered that the number of serotonin transporters or “vacuum cleaners” that remove this chemical were greater in winter in healthy people. In addition, the group found that decreased sunlight was correlated with increased serotonin transporter levels and vice versa.
At CAMH, under Meyer’s supervision, Department of Pharmacology PhD student Andrea Tyrer is investigating neurochemical changes in SAD by imaging the brain using positron emission tomography scanning.
Meyer and Tyrer hypothesize that changes in environmental factors, such as light exposure, might facilitate the winter increase in these serotonin “vacuum cleaners” and the development of seasonal depression.
Tyrer is investigating whether there is a larger change in the number of serotonin “vacuum cleaners” in those with SAD than compared to healthy volunteers. She is also studying how bright light therapy can prevent this winter elevation in serotonin transporter levels to treat seasonal depressive symptoms by brain scanning individuals with SAD before and after this treatment.
If it is found that greater seasonal fluctuations in serotonin transporter levels occur in people with SAD, this knowledge could be used to develop strategies to prevent or treat SAD.
In addition, only 55 per cent of individuals suffering from seasonal depressive symptoms fully remit after light therapy. If light therapy is shown to prevent the winter increase in serotonin transporter levels, these findings would provide a way to improve this treatment using brain scanning to determining what aspects (i.e. colour, intensity, time of day) of light exposure best reduce serotonin transporter levels.
The expected outcomes of this research will enhance our knowledge of this understudied area so as to provide relief for those who suffer from SAD during long, dark Canadian winters.
