A study of over 3,000 people shows that versions of the gene EPHX2 are strongly associated with the condition. The findings suggest that the likelihood of developing anorexia may be tied to both genetic and social factors.
Professor Nicholas Schork of The Scripp Research Institute in California, USA, a senior investigator for the study, said: 'These findings point in a direction that probably no one would have considered taking before'.
Around one in 250 women and one in 2,000 men will develop anorexia nervosa during their lives, a 2004 report from the National Institute for Health and Care Excellence suggests. Patients restrict their eating severely, often continuing to believe they are overweight despite being dangerously malnourished. The resulting severe emaciation can be fatal and some consider anorexia as one of the most lethal psychiatric diseases.
Anorexia was long considered to be caused by psychological or social factors such as stress, pressures at the onset of puberty and cultural pressures. But twin studies have suggested that genetic factors may be an important influence.
In this study researchers initially probed the genomes of 334 anorexia patients. After drawing up a list of more than 150 candidate genes already linked to feeding behaviour or metabolism, they found a few that showed statistical signs of a linkage with anorexia.
'We thought that with further studies this EPHX2 finding might go away, or appear less compelling, but we just kept finding evidence to suggest that it plays a role in anorexia', said Professor Schork.
The data was also compared with data from long term heart disease research showing that mutations in EPHX2 can cause changes in the relationship between cholesterol levels and weight gain.
It is not yet known how disruption of cholesterol metabolism might contribute to development of anorexia. Some studies have found that patients with anorexia nervosa have elevated cholesterol levels, while other research suggests that elevated cholesterol levels are linked with heightened mood for some people.
Discussing potential mechanisms, Professor Schork said: 'The hypothesis would be that in some anorexics the normal metabolism of cholesterol is disrupted, which could influence their mood as well as their ability to survive despite severe caloric restriction'.