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. 2021 Jan;51(1):62-69.
doi: 10.1017/S0033291719002976. Epub 2019 Oct 29.

Genetic and environmental contributions to diagnostic fluctuation in anorexia nervosa and bulimia nervosa

Shuyang Yao  1 , Henrik Larsson  1   2 , Claes Norring  3 , Andreas Birgegård  3 , Paul Lichtenstein  1 , Brian M DʼOnofrio  1   4 , Catarina Almqvist  1   5 , Laura M Thornton  6 , Cynthia M Bulik  1   6   7 , Ralf Kuja-Halkola  1
Affiliations

Genetic and environmental contributions to diagnostic fluctuation in anorexia nervosa and bulimia nervosa

Shuyang Yao et al. Psychol Med. 2021 Jan.

Abstract

Background: Anorexia nervosa and bulimia nervosa are two severe eating disorders associated with high premature mortality, suicidal risk and serious medical complications. Transition between anorexia nervosa and bulimia nervosa over the illness course and familial co-aggregation of the two eating disorders imply aetiological overlap. However, genetic and environmental liabilities to the overlap are poorly understood. Quantitative genetic research using clinical diagnosis is needed.

Methods: We acquired a clinical diagnosis of anorexia nervosa (prevalence = 0.90%) and bulimia nervosa (prevalence = 0.48%) in a large population-based sample (N = 782 938) of randomly selected full-sisters and maternal half-sisters born in Sweden between 1970 and 2005. Structural equation modelling was applied to quantify heritability of clinically diagnosed anorexia nervosa and bulimia nervosa and the contributions of genetic and environmental effects on their overlap.

Results: The heritability of clinically diagnosed anorexia nervosa and bulimia nervosa was estimated at 43% [95% confidence interval (CI) (36-50%)] and 41% (31-52%), respectively, in the study population, with the remaining variance explained by variance in unique environmental effects. We found statistically significant genetic [0.66, 95% CI (0.49-0.82)] and unique environmental correlations [0.55 (0.43-0.66)] between the two clinically diagnosed eating disorders; and their overlap was about equally explained by genetic and unique environmental effects [co-heritability 47% (35-58%)].

Conclusions: Our study supports shared mechanisms for anorexia nervosa and bulimia nervosa and extends the literature from self-reported behavioural measures to clinical diagnosis. The findings encourage future molecular genetic research on both eating disorders and emphasize clinical vigilance for symptom fluctuation between them.

Keywords: Anorexia nervosa; behavioural genetics; bulimia nervosa; clinical diagnosis; eating disorders; genetic epidemiology; medical register; sibling design.

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Figures

Fig. 1.
Fig. 1.
Path diagram of the additive genetic effects and genetic correlations in a bivariate model of anorexia nervosa and bulimia nervosa. AN, anorexia nervosa; BN, bulimia nervosa. A1 represents the latent additive genetic effect that contributes a1 to anorexia nervosa; A2 represents the latent additive genetic effect that contributes a2 to bulimia nervosa. The additive genetic correlation between anorexia nervosa and bulimia nervosa is represented by rA. Parameters a1, a2 and rA are the unknown parameters. The dashed double arrows indicate the genetic sharing between two sisters in a pair; they are 0.5 for full-sisters and 0.25 for maternal half-sisters.
See this image and copyright information in PMC

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