Individuals who suffer from social phobia tend to produce too much serotonin, according to a new study conducted by Finnish researchers at Uppsala University. In fact, the more serotonin they produce, the more anxious they become in social situations. These findings are in complete contrast to those of previous research which linked social anxiety to the production of too little serotonin.

Many people feel anxious in new social situations or are afraid to speak in front of an audience, but if the anxiety is persistent and severely lowers a person’s quality of life, it becomes a disability.

Since the belief up until now has been that social anxiety is triggered from too little serotonin, social phobia is commonly medicated using selective serotonin reuptake inhibitors (SSRI) medications. SSRIs increase the amount of available serotonin in the brain.

In the new study, published in the scientific journal JAMA Psychiatry, the research team, led by professors Mats Fredrikson and Tomas Furmark, used a PET camera and a special tracer to measure chemical signal transmission by serotonin in the brain.

They discovered that participants with social phobia produced too much serotonin in a part of the brain’s fear center, known as the amygdala. The more serotonin produced, the more anxious the patients were in social situations.

A nerve cell, which sends signals using serotonin, first releases serotonin into the space between the nerve cells. The nerve signal arises when serotonin attaches itself to the receptor cell. The serotonin is then released from the receptor and pumped back to the original cell.

“Not only did individuals with social phobia make more serotonin than people without such a disorder, they also pump back more serotonin. We were able to show this in another group of patients using a different tracer which itself measures the pump mechanism.

“We believe that this is an attempt to compensate for the excess serotonin active in transmitting signals,” says Andreas Frick, a doctoral student at Uppsala University Department of Psychology.

The novel findings are a giant leap forward when it comes to identifying changes in the brain’s chemical messengers in people who suffer from anxiety. Previous research has shown that nerve activity in the amygdala is higher in people with social phobia and thus that the brain’s fear center is over-sensitive. The new study shows that an overabundance of serotonin is part of the underlying reason.

“Serotonin can increase anxiety and not decrease it as was previously often assumed,” says Frick.

Source: Uppsala University