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Anorexia arises from gene-environment interaction

(Vienna, 17 Dec. 2010) Parenting style and genetic disposition are key factors for the onset of anorexia nervosa. Researchers from MedUni Vienna headed by Ao. Univ. Prof. Dr. Andreas Karwautz have published the findings of an international multi-centre study.

Anorexia is the most serious illness known to psychiatry. Its mortality rate is twice as high as that of serious depressive disorder. The burden which this disease means for the families is comparable with that of schizophrenic psychoses. 95% of those affected are young girls and women, and around 100-140 new sufferers are registered each year in Vienna alone. Psychosocial risk factors, such as an unfavourable, autonomy-threatening parental style with excessive control, abuse, difficult life events and social isolation have been proven to be of considerable relevance for anorexia.

Previous studies have also shown that the people who are affected by serious depression are especially those who, as well as serious psychosocial difficulties, also have genetic mutations in the promoter region of the serotonin transporter gene.
Andreas Karwautz from the Department of Child and Adolescent Psychiatry at MedUni Vienna followed this approach and integrated the biological and psychosocial factors as part of an international multi-centre study on anorexia. Here he also proved the effectiveness for anorexia of an interaction already known for depressive disorders (Caspi et al., 2003).

It became apparent that an unfavourable parenting style in the period up to the onset of anorexia nervosa only has an unfavourable effect if there is a mutation of the promoter region of the serotonin transporter. Highly-potent psychosocial stressors – such as difficult life events, interpersonal problems or mocking body-related remarks – were confirmed as causally relevant irrespective of genetic aspects. Here the particularly pronounced SS genotype reacted disproportionately strongly to stressful events compared with the weaker LS genotype. Trial participants without this mutation did not have an increased risk of anorexia because of an unfavourable parenting style.

In total 128 pairs of sisters from Vienna, London and Barcelona were examined in this study. Here one sister was healthy while the other had anorexia nervosa. There were no discernible differences for any specific country.

Head of the study Karwautz, who has specialised in psychosocial risk research with adolescent psychiatric disorders and qualified as a professor in this field at MedUni Vienna in 2002, explains: “For the first time we have been able to show paradigmatically for anorexia nervosa that parental conduct is etiologically effective for anorexia nervosa as part of an interactional model. This is an important discovery for therapy and counselling.“

The study has been published in the top-ranking psychiatry journal “Molecular Psychiatry”:
» Gene–environment interaction in anorexia nervosa: relevance of non-shared environment and the serotonin transporter gene; A F K Karwautz, G Wagner, K Waldherr, I W Nader, F Fernandez-Aranda, X Estivill, J Holliday, D A Collier and J L Treasure; Molecular Psychiatry, doi:10.1038/mp.2010.12