Individual-specific risk factors for anorexia nervosa: a pilot study using a discordant sister-pair design.
BACKGROUND
The aim of this pilot study was to examine which unique factors (genetic and environmental) increase the risk for developing anorexia nervosa by using a case-control design of discordant sister pairs.


METHODS
Forty-five sister-pairs, one of whom had anorexia nervosa and the other did not, were recruited. Both sisters completed the Oxford Risk Factor Interview for Eating Disorders and measures for eating disorder traits, and sib-pair differences. Blood or cheek cell samples were taken for genetic analysis. Statistical power of the genetic analysis of discordant same-sex siblings was calculated using a specially written program, DISCORD.


RESULTS
The sisters with anorexia nervosa differed from their healthy sisters in terms of personal vulnerability traits and exposure to high parental expectations and sexual abuse. Factors within the dieting risk domain did not differ. However, there was evidence of poor feeding in childhood. No difference in the distribution of genotypes or alleles of the DRD4, COMT, the 5HT2A and 5HT2C receptor genes was detected. These results are preliminary because our calculations indicate that there is insufficient power to detect the expected effect on risk with this sample size.


CONCLUSIONS
A combination of intrinsic and extrinsic factors increases the risk of developing anorexia nervosa. It would, therefore, be informative to undertake a larger study to examine in more detail the unique genetic and environmental factors that are associated with various forms of eating disorders.
Department of Biostatistics and Computing, Maudsley and Bethlem Trust Hospital, University of London.
A
A
Karwautz
S
S
Rabe-Hesketh
X
X
Hu
J
J
Zhao
P
P
Sham
D A
DA
Collier
J L
JL
Treasure
D000293:Adolescent; D000328:Adult; D000483:Alleles; D000856:Anorexia Nervosa / Q000209:etiology* / Q000235:genetics* / Q000523:psychology; D016022:Case-Control Studies; D002648:Child; D005260:Female; D005500:Follow-Up Studies; D005838:Genotype; D006801:Humans; D008780:Methyltransferases / Q000235:genetics; D010865:Pilot Projects; D044402:Receptor, Serotonin, 5-HT2A; D044405:Receptor, Serotonin, 5-HT2C; D017448:Receptors, Dopamine D2 / Q000235:genetics; D050638:Receptors, Dopamine D4; D011985:Receptors, Serotonin / Q000235:genetics; D011795:Surveys and Questionnaires
C493599:DRD4 protein, human; D044402:Receptor, Serotonin, 5-HT2A; D044405:Receptor, Serotonin, 5-HT2C; D017448:Receptors, Dopamine D2; D011985:Receptors, Serotonin; D050638:Receptors, Dopamine D4; D008780:Methyltransferases; C019608:caffeate O-methyltransferase