People with seasonal affective disorder have an unhelpful way of controlling the "happy" brain signalling compound serotonin during winter months, brain scans reveal. As the nights draw in, production of a transporter protein ramps up in SAD, lowering available serotonin. The work will be presented this week at a neuropsychopharmacology conference.
The University of Copenhagen researchers who carried out the trial say their findings confirm what others have suspected – although they only studied 11 people with Sad and 23 healthy volunteers for comparison. Using positron emission tomography (PET) brain scans, they were able to show significant summer-to-winter differences in the levels of the serotonin transporter (SERT) protein in Sad patients. The Sad volunteers had higher levels of SERT in the winter months, corresponding to a greater removal of serotonin in winter, while the healthy volunteers did not.
Lead researcher, Dr Brenda Mc Mahon, 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.