Brain scans show cause of seasonal affective disorder

Scientists say they have identified the underlying reason why some people are prone to the winter blues, or seasonal affective disorder (SAD).

People with Sad 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 was presented this week at the ECNP congress in Berlin. Source: European College of Neuropsychopharmacology

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."

Prof Siegfried Kasper, of the European College of Neuropsychophar­macology, which this year is holding its annual congress in Berlin, 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."

There are a range of treatments available for Sad, such as light therapy and cognitive behavioural therapy.

"We know that eating a balanced diet, cutting down on caffeine and getting some exercise can help, as can spending as much time as possible outdoors because - even when it's overcast - light will be higher than indoors."

Sad affects about two million people in the UK, and more than 12 million people across northern Europe.

View Research Study here: Seasonal difference in brain serotonin transporter binding predicts symptom severity in patients with seasonal affective disorder. 

View BBC article here