Seasonal Depression Tied to Serotonin
People With Seasonal Affective Disorder May Have Less of the Brain Chemical in Winter
Sept. 19, 2007 -- People with seasonal affective disorder (SAD) may have
lower levels of the brain chemical serotonin in winter than other people,
according to a new study.
But those lower serotonin levels bounce back to normal if their seasonal
depression is treated -- and in summer.
Researchers say the finding could lead to improved treatments for SAD,
which is a form of seasonal depression that worsens in winter and improves in
summer. Symptoms include weight gain, increased need for sleep, irritability,
and inability to concentrate.
SAD Tied to Serotonin Levels
Previous studies have shown that in depression the brain has too little
serotonin, but it’s not known exactly why.
In this study, researchers at the Medical University of Vienna looked at how
the brain removes serotonin through the serotonin transporter and compared the
rate of removal in 73 people with untreated seasonal affective disorder and 70
The results, published in Neuropsychopharmacology, showed serotonin
was removed from the brain at a faster rate among those with seasonal
depression, causing serotonin levels to drop below normal. But serotonin
removal rates returned to normal with treatment and during the summer
Researchers say the results could help identify people at risk for seasonal
depression and more effective treatments.
Currently available treatments for seasonal affective disorder include
increased exposure to light sources, such as natural sunlight or a light box,