23 November 2009
ByAppeared in BioNews 535
In the first study of its kind, researchers in the US have identified a genetic variant that appears to influence both a person's ability to empathise, and how they respond to stress. The research, by a team from Oregon State University and the University of California at Berkeley and published in the journal Proceedings of the National Academy of Sciences, may shed significant light on scientists' understanding of autism, which is characterised by problems with empathy and social communication. It may also help to understand other more general aspects of human psychology, such as why some people may be relatively more empathic and stress reactive.
The researchers focused on a region of the OXTR gene, which codes for neuroreceptor cells throughout the body that serve as 'docking stations' for a chemical called oxytocin. Oxytocin is a hormone regulated by the brain that is best known for its role in pair bonding and emotional attachment, but is also important in social recognition, female reproduction (in labour and breastfeeding), and in dampening negative emotional responses. Previous research in humans and mice has shown that even under conditions of stress, oxytocin has a pronounced calming effect when the chemical is puffed up the nose or pumped into the bloodstream. This evidence prompted the researchers to look for genetic variations that might influence the ability to produce more or less of this hormone.
The team studied the DNA of 200 university students to establish whether they carried genetic variations in this region of the OXTR gene, with three combinations possible; AA, AG or GG. People with the AA or AG variants are more likely to develop autism or to show less spontaneous warmth towards their children. The AA and AG gene group were not statistically different, so they were grouped together and compared in all tests with the GG group. Subjects then participated in two tests. The first involved listening to white noise through headphones to stimulate stress. The second test involved looking at a series of photographs of pairs of eyes, and idenifying the emotional state of the person in the picture, a test of empathy known as 'reading the mind in the eyes'. In addition, the study participants filled out questionnaires rating their own levels of empathy and ability to deal with stress.
The team found that people of both sexes who carried the GG type performed better on both tests than those with the other gene variants. Although women were more sensitive to the stress test than men, both sexes in the GG group showed lower heart rates during this task, indicating that they were more resistant to stress and anxiety. In addition, they were 22.7 per cent less likely to make a mistake on the empathy test.
According to Dr Sarina Rodrigues, assistant professor from Oregon State University and member of the research team, the study 'lends credence to the claim that this genetic variation of oxytocin influences emotional processing and other-oriented behaviour'. However she cautioned that most people who have the version associated with lower scores on the test are still perfectly empathic and caring individuals; Dr Rodrigues herself does not have the GG version of the gene. Rather, she pointed to how the findings 'can help us understand that some of us are born with a tendency to be more empathic and stress reactive than others, and that we should reach out to those who may be naturally closed off from people, because social connectivity and belongingness benefits everyone.'