David Baxter PhD
Late Founder
Anxiety disorders not all in the mind
Tue, May 13 2008
Researchers find link between altered dopamine activity and social anxiety disorder
Using single-photon emission computed tomography (SPECT), researchers in The Netherlands were able to detect biochemical differences in the brains of individuals with social anxiety disorder (also known as social phobia), providing evidence of a long-suspected biological cause for the dysfunction.
The study compared densities of elements of the serotonin and dopamine neurotransmitter systems in the brains of 12 people diagnosed with social anxiety disorder, but who had not taken medication to treat it, and a control group of 12 healthy people who were matched by sex and age.
Both groups were injected with a radioactive compound that binds with elements of the brain's serotonin and dopamine systems. Once administered, the radiotracer revealed functional alterations in these 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). The altered uptake activity in these 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, M.D., Ph.D., at the department of psychiatry and the Leiden Institute for Brain and Cognition at the Leiden University Medical Center, Leiden. "It demonstrates that social anxiety has a physical, brain dependent component."
Serotonin and dopamine neurotransmitters act upon receptors in the brain. If these neurotransmitter systems are out of balance, messages do not propagate through the brain properly. This can alter the way the brain reacts to normal social situations, leading to anxiety.
Other neuroimaging studies have shown abnormalities in glucose and oxygen consumption in the brain, according to van der Wee, who also points to causality as an additional issue. "Most of the people involved in these earlier studies were known to be already suffering from the disorder, so we do not know if the abnormalities were present before the onset of the disorder," he said.
Based on earlier studies, some researchers have suggested that social anxiety disorder is a result of the interplay between a genetic or acquired biological vulnerability and environment. More recent research has indicated that social anxiety disorder might be related to an imbalance of the serotonin system. This is the first time the brain's dopaminergic system was examined directly.
"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.
According to the National Institute of Mental Health, social anxiety disorder affects approximately 15 million American adults and is the third most common mental disorder in the United States, after depression and alcohol dependence. The essential feature of the disorder is the fear of being evaluated by others, with the expectation that such an assessment will be negative and embarrassing. It tends to run a chronic and unremitting course and often leads to the development of alcoholism and depression. The disorder most often surfaces in adolescence or early adulthood, but it can occur at any time, including childhood.
Source: van der Wee NJ, van Veen JF, Stevens H, et al. Increased Serotonin and Dopamine Transporter Binding in Psychotropic Medication-Na?ve Patients with Generalized Social Anxiety Disorder Shown by 123I-?-(4-Iodophenyl)-Tropane SPECT. J Nucl Med 2008 49: 757-763. [Abstract]
Tue, May 13 2008
Researchers find link between altered dopamine activity and social anxiety disorder
Using single-photon emission computed tomography (SPECT), researchers in The Netherlands were able to detect biochemical differences in the brains of individuals with social anxiety disorder (also known as social phobia), providing evidence of a long-suspected biological cause for the dysfunction.
The study compared densities of elements of the serotonin and dopamine neurotransmitter systems in the brains of 12 people diagnosed with social anxiety disorder, but who had not taken medication to treat it, and a control group of 12 healthy people who were matched by sex and age.
Both groups were injected with a radioactive compound that binds with elements of the brain's serotonin and dopamine systems. Once administered, the radiotracer revealed functional alterations in these 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). The altered uptake activity in these 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, M.D., Ph.D., at the department of psychiatry and the Leiden Institute for Brain and Cognition at the Leiden University Medical Center, Leiden. "It demonstrates that social anxiety has a physical, brain dependent component."
Serotonin and dopamine neurotransmitters act upon receptors in the brain. If these neurotransmitter systems are out of balance, messages do not propagate through the brain properly. This can alter the way the brain reacts to normal social situations, leading to anxiety.
Other neuroimaging studies have shown abnormalities in glucose and oxygen consumption in the brain, according to van der Wee, who also points to causality as an additional issue. "Most of the people involved in these earlier studies were known to be already suffering from the disorder, so we do not know if the abnormalities were present before the onset of the disorder," he said.
Based on earlier studies, some researchers have suggested that social anxiety disorder is a result of the interplay between a genetic or acquired biological vulnerability and environment. More recent research has indicated that social anxiety disorder might be related to an imbalance of the serotonin system. This is the first time the brain's dopaminergic system was examined directly.
"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.
According to the National Institute of Mental Health, social anxiety disorder affects approximately 15 million American adults and is the third most common mental disorder in the United States, after depression and alcohol dependence. The essential feature of the disorder is the fear of being evaluated by others, with the expectation that such an assessment will be negative and embarrassing. It tends to run a chronic and unremitting course and often leads to the development of alcoholism and depression. The disorder most often surfaces in adolescence or early adulthood, but it can occur at any time, including childhood.
Source: van der Wee NJ, van Veen JF, Stevens H, et al. Increased Serotonin and Dopamine Transporter Binding in Psychotropic Medication-Na?ve Patients with Generalized Social Anxiety Disorder Shown by 123I-?-(4-Iodophenyl)-Tropane SPECT. J Nucl Med 2008 49: 757-763. [Abstract]
