Extra Brain Chemical May Cause Winter Blues

(September 11, 2008) - A higher level of a certain brain chemical during the winter months may be the reason many people get the so-called winter blues or cabin fever. Researchers say they have discovered greater levels of serotonin transporter in the brain (Read about "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. (Read about "Depressive Illnesses")

The researchers 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.