As the days get shorter, for many the risk of depression increases. New research from the European College of Neuropsychopharmacology conference in Berlin confirms why some people suffer from the winter blues while others get through the winter without any problems.
The new study from scientists at the University of Copenhagen in Denmark finds that people with seasonal affective disorder (SAD) show significant seasonal differences in the way they regulate the neurotransmitter serotonin in comparison to the majority of the population.
SAD affects a significant amount of people as daylight levels drop in autumn. At Northern European latitudes (for example all of Scandinavia, Glasgow, and Moscow) around one person in six suffers from SAD.
Researchers at the University of Copenhagen used positron emission tomography (PET) to perform a longitudinal study on 11 SAD patients and 23 healthy individuals. They discovered significant summer to winter differences in the levels of the serotonin transporter (SERT) protein.
SAD patients showed higher levels of SERT in the winter months, corresponding to a greater removal of serotonin in winter.
Serotonin (also known as 5-HT) is a neurotransmitter which affects mood. Many antidepressant drugs, such as SSRIs (selective serotonin reuptake inhibitors, such as Prozac) work by allowing serotonin to be retained in the synapse where it exerts its effects.
Lead researcher and M.D./Ph.D. student Brenda McMahon said, “We believe that we have found the dial the brain turns when it has to adjust serotonin to the changing seasons. The serotonin transporter (SERT) carries serotonin back into the nerve cells where it is not active, so the higher the SERT activity the lower the activity of serotonin.
“Sunlight keeps this setting naturally low, but when the nights grow longer during the autumn, the SERT levels increase, resulting in diminishing active serotonin levels. Many individuals are not really affected by SAD, and we have found that these people don’t have this increase in SERT activity, so their active serotonin levels remain high throughout the winter.”
The SAD patients had an average five percent higher SERT level in the winter compared to the summer, whereas the healthy participants on average showed no significant change.
Commenting for the ECNP, Professor Siegfried Kasper (Vienna) said, “SERT fluctuations associated with SAD have been seen in previous studies, but this is the first study to follow patients through summer and winter comparisons. It seems to offer confirmation that SERT is associated with SAD.”
Source: Science Daily