Fluctuations in Serotonin Transport May Explain Winter Blues

    TORONTO, Sept. 8 /CNW/ - Why do many Canadians get the winter blues? In
the first study of its kind in the living human brain, Dr. Jeffrey Meyer and
colleagues at the Centre for Addiction and Mental Health (CAMH) have
discovered greater levels of serotonin transporter in the brain in winter than
in summer. These findings have important implications for understanding
seasonal mood change in healthy people, vulnerability to seasonal affective
disorders and the relationship of light exposure to mood.
    CAMH's scientific team discovered that the serotonin transporter levels
were significantly higher in all investigated brain regions in individuals
studied in fall/winter, compared to those studied in spring/summer in a study
of healthy subjects. Serotonin transporters remove serotonin so this discovery
argues that there is more serotonin removal in the fall/winter as compared to
spring/summer. Also, the higher serotonin transporter binding values occurred
at times when there is less sunlight. This is the first time scientists have
found differences in serotonin transporter levels in the brain in fall/winter
versus spring/summer.
    Serotonin is involved in regulating physical functions such as eating and
energy balance, and emotional functions like mood and energy levels. These
phenomena vary across the seasons and the molecular background for why this
happens was previously unknown. For this study, Dr. Jeffrey Meyer and his team
used a world-leading positron emission tomography (PET) technology (originally
created at CAMH by Dr. Alan Wilson) to detect these seasonal variations in
serotonin transporter binding (the process that removes serotonin) in the
living human brain and correlations between serotonin binding and duration of
daily sunshine.
    As Dr. Meyer explains, this is "an important lead in understanding how
season changes serotonin levels. This offers an explanation for why some
healthy people experience low mood and energy in the winter, and why there is
a regular reoccurrence of depressive episodes in fall and winter in some
vulnerable individuals. The next steps will be to understand what causes this
change and how to interfere with it."
    According to the world health organization, major depressive disorder is
the fourth leading cause of death and disability. Dr. Meyer points out that,
"the future for treatment should be to prevent the illness itself." The
presence of higher serotonin transporter levels might explain why many people
experience the onset of major depressive episodes in the fall and winter.
"Over the following years, we intend to determine the specifics of the
environment (such as light exposure) that influence serotonin transporter
levels so as to determine what is the optimal environment to prevent illness.
In the future, it may be that just like we have lifestyle recommendations to
prevent heart disease, we will have lifestyle recommendations to prevent major
depressive disorder."

    The Centre for Addiction and Mental Health (CAMH) is Canada's largest
mental health and addiction teaching hospital, as well as one of the world's
leading research centres in the area of addiction and mental health. CAMH
combines clinical care, research, education, policy development and health
promotion to transform the lives of people affected by mental health and
addiction issues.

    CAMH is fully affiliated with the University of Toronto, and is a Pan
American Health Organization/World Health Organization Collaborating Centre.

For further information:

For further information: To arrange interviews please contact Michael
Torres, Media Relations, CAMH, at (416) 595-6015

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