Scientists in The Netherlands have unearthed evidence that altered dopamine activity in the brain may give rise to social phobia.
The finding reported by researchers at the Leiden University Medical Center results from a study wherein densities of elements of the serotonin and dopamine neurotransmitter systems were compared in the brains of 12 persons diagnosed with social anxiety disorder, and 12 healthy people in the control group.
The persons in the experimental group had never taken medication to treat the disorder, and the subjects in the two groups were matched by sex and age.
The researchers injected both groups with a radioactive compound that binds with elements of the brain's serotonin and dopamine systems.
The radiotracer revealed functional alterations in those systems by measuring the radioactive binding in the thalamus, midbrain and pons (known to be acted upon by serotonin) and in the striatum (known to be acted upon by dopamine).
In their study report, published in the Journal of Nuclear Medicine, the researchers revealed that the altered uptake activity in those regions indicated a greater level of disordered function.
"Our study provides direct evidence for the involvement of the brain's dopaminergic system in social anxiety disorder in patients who had no prior exposure to medication," said Dr. van der Wee of the department of psychiatry and the Leiden Institute for Brain and Cognition.
"It demonstrates that social anxiety has a physical, brain dependent component," added the researcher.
The study report suggests that serotonin and dopamine are neurotransmitters that act upon receptors in the brain.
It further says that any irregularity in the neurotransmitters can hinder the proper passage of messages through the brain, altering the way the brain reacts to normal social situations, and leading to anxiety.
According to van der Wee, this is the first time the brain's dopaminergic system has been examined directly to see whether it has any link with the social anxiety disorder.
"Although there are no direct implications for treatment as a result of this study yet, it is another piece of evidence showing biological abnormalities, which may lead to new therapeutic approaches and insight into the origins of the disorder," said Dr. van der Wee.