An Investigation of Eating Disorder Neurocognitive and Behavioural Endophenotypes in Twins
Background: Cognitive styles, emotional processing and behavioural traits are involved in the aetiology and maintenance of eating disorders. Some of these traits are present post recovery and in first-degree relatives suggesting that they may be endophenotypes. Aims: The aim of this study was to examine cognitive styles, emotional processing and behavioural traits in female twins with eating disorders in order to explore their genetic basis. Such investigations will increase our knowledge of the aetiological architecture that underlies eating disorders. Methods: In a sample of twins representative of the population (n=3338), the heritability of psychological symptoms thought to be related to eating disorders was estimated using structural equation modelling of questionnaire data. In a more in-depth face-to-face study, a smaller group of 114 clinical and control twins (n=53 met lifetime DSM-IV eating disorder criteria, n=19 non-eating disorder cotwins and n=42 controls) were assessed using a semi-structured interview and an objective assessment of cognitive styles, emotional processing and behavioural traits. To explore the heritability of these, within-pair-correlations were calculated and generalised estimating equations compared probands with non-eating disorder cotwins and controls. Results: In the population sample, the psychological symptoms related to eating disorders were found to be moderately heritable. In the clinical sample of twins, there appeared a genetic basis to the life course of the eating disorder. Childhood traits reflecting an obsessive compulsive personality and lifetime impulsive behaviours were found to be familial traits. Analysis of cognitive styles indicated they had a genetic and familial basis and emotional processing also showed a genetic and familial basis at trend level. There was some evidence of altered reward sensitivity in people with bulimic disorders, although less evidence of a substantial genetic basis. Conclusions: Psychological symptoms related to eating disorders were moderately heritable in the population twin sample. The clinical studies were exploratory, in part due to the limited sample size. Some elements of the findings lent support to cognitive and emotional processing traits being endophenotypes for eating disorders. However the relatively small sized differences between clinical and control samples as well as the differences between age groups and across the diagnostic spectrum, demonstrates that these particular measures may be restricted in their ability to inform the future diagnosis and taxonomy of eating disorders. Future studies with larger samples are required to confirm the present study’s findings.
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