'Bonding' hormone may alleviate social anxiety

Swedish and British researchers have found that the hormone oxytocin can inhibit feelings of anxiety in specific individuals. Their discovery might lead to a better understanding and the improved treatment of disorders in which people feel distressed when meeting others, such as autism and social phobia.

Oxytocin is a neuropeptide that is secreted by the body during massage, childbirth and breastfeeding to induce a calming, analgesic effect. Animal studies have also shown that oxytocin promotes social interaction, such as during the courting process. The hormone has a direct influence on the amygdala, a brain area that is important for social interaction and for identifying immediate emotional threats.

In this new study scientists at the Swedish medical university Karolinska Institutet and the Welcome Trust Functional Imaging Laboratory in London demonstrated that oxytocin has a more targeted effect than simply producing a general feeling of wellbeing.

Subjects were shown pictures of four different faces, two of which were combined with a tiny, harmless but uncomfortable electric shock. As expected, the researchers found that the faces associated with the shock were considered more unpleasant than the others. However, when half of the subjects were then given oxytocin spray and the other half a placebo spray, an interesting change was brought about.

"When we showed the oxytocin group the two faces again that had previously been associated with the shock, they no longer found them disagreeable, while those who had received the placebo still found them so," says Dr Predrag Petrovic from the Department of Clinical Neuroscience at Karolinska Institutet.

Using an fMRI scanner, the team also found that subjects who had developed shock-induced feelings of anxiety for certain faces exhibited, when shown these faces, higher levels of activity in two brain areas - the amygdalae and the 'fusiform face area' - that process unpleasant and threatening faces. These activity levels then dropped when they were given oxytocin, but not when given the placebo.

"This suggests that oxytocin can reduce anxiety and increase the chances of social contact for people with certain types of psychiatric disorder," says Dr Petrovic. "There are also previous studies to show that oxytocin can inhibit amygdala activity, which tells us that we should see this as an opportunity for new forms of treatment."

The study was conducted at the Welcome Trust Functional Imaging Laboratory in London and the data analysed in London and at Karolinska Institutet in Stockholm and was co-financed by the Swedish Research Council.

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Petrovic P, Kalisch R, Singer T, Dolan RJ. Oxytocin attenuates affective evaluations of conditioned faces and amygdala activity. J Neurosci. 2008 Jun 25;28(26):6607-15.   [Abstract]