Although the symptoms of generalized social anxiety disorder are sometimes alleviated by antidepressant medicines such as Prozac, and tranquilizers such as Valium, these medications do not work for everyone. But a former NARSAD grantee and members of an international research team now report progress in understanding a new potential medical treatment for anxiety, which affects approximately 40 million American adults.

The researchers looked at the anxiety-reducing effects of oxytocin, a neurotransmitter sometimes called the “love hormone” for its ability to reduce stress and promote pro-social behaviors such as trust, empathy, and openness to social risk. Oxytocin has now been shown to make the amygdala less reactive to pictures of threatening or fearful faces. Previous research identified the amygdala as a crucial brain area for emotional processing.

In a paper appearing August 6th in Neuropsychopharmacology, researchers expanded on previous findings showing oxytocin’s influence on the amygdala. The research team was led by Stephanie M. Gorka, Ph.D., of the University of Illinois and included Pradeep Nathan, Ph.D., of Cambridge University (formally Monash University), recipient of a 2007 NARSAD Independent Investigator grant. They examined how oxytocin affects connections between the amygdala and other parts of the brain in people with anxiety disorder.

As study participants viewed fearful faces, brain scans with functional MRI showed that the amygdala communicated significantly less with other parts of the brain in those with generalized social anxiety, compared to those not diagnosed with anxiety disorder.  The less connected the amygdala was to other brain regions, the higher the anxious participants’ baseline stress levels were. Importantly, oxytocin reversed those trends by increasing amygdala connectivity in anxiety patients, while decreasing amygdala connectivity in everyone else.

These findings suggest that oxytocin can have specific effects in people with anxiety through its influence on the amygdala. More broadly, the fact that oxytocin had opposite effects in the two participant groups indicates that the neurotransmitter’s success in reducing stress and promoting social behavior depends on individual brain characteristics, which differ between those with anxiety and those without the disorder. Thus, while oxytocin continues to show promise as a potential treatment for anxiety, it may not promote positive social behaviors in everyone.

As noted by Professor Nathan and colleagues, these findings are preliminary. To better assess how presumed changes in the brain influence actual experiences of anxiety, further research is needed to test oxytocin on more people with and without anxiety disorders. This, the scientists say, will be crucial in determining whether and exactly how oxytocin can improve treatment for anxiety disorders.

Read the abstract.