Fluctuations in Serotonin Transport May Explain Winter Blues

Why do many Canadians get the winter blues?  In the first study of its kind in the living human brain, CAMH’s Dr. Jeffrey Meyer and colleagues 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.

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.”

For more information, visit  Fluctuations in Serotonin Transport May Explain Winter Blues.  A copy of the study's abstract is available in the September 2008 issue of Archives of General Psychiatry. 

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