Levels of the brain chemical serotonin are too high in people with social phobia, rather than too low as previously believed, a new study says.
Oversensitive fear centre
Researchers at Uppsala University in Sweden conducted brain scans on volunteers and found that those with social phobia – also called social anxiety disorder – produced too much serotonin in the amygdala, which is part of the brain's fear centre.
The more serotonin their brains produced, the more anxious they were in social situations, the investigators found.
"Serotonin can increase anxiety, and not decrease it as was previously often assumed," researcher Andreas Frick, a doctoral student in the psychology department at Uppsala, said in a university news release.
Read: Anxiety disorders
The study was published in the journal JAMA Psychiatry.
Serotonin, which is produced by nerve cells, helps to relay messages from one area of the brain to another.
Previous research showed that nerve activity in the amygdala is higher in people with social phobia and that the fear centre in their brain is oversensitive. These new findings suggest that too much serotonin plays a role.
Social phobia is often treated with drugs called selective serotonin reuptake inhibitors (SSRIs), which increase the amount of available serotonin in the brain.
Image: Social phobia from Shutterstock