Season of birth bias and anorexia nervosa: Results from an international collaboration

Authors

  • Eirin Winje Cand.Psychol,

    Corresponding author
    1. Division of Mental Health and Addiction, Oslo University Hospital, Oslo, Norway
    • Oslo University Hospital, Regional department for eating disorders, PB 4950 Nydalen, Oslo, Norway
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  • Anne-Kari Torgalsbøen PhD,

    1. Department of Psychology, University of Oslo, Oslo, Norway
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  • Cathrine Brunborg MS,

    1. Unit for Biostatistics and Epidemiology, Oslo University Hospital, Oslo, Norway
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  • Bryan Lask FRCPsych

    1. Division of Mental Health and Addiction, Oslo University Hospital, Oslo, Norway
    2. Service for Eating Disorders, Ellern Mede, London, United Kingdom
    3. Department of Child and Adolescent Mental Health, Gt. Ormond St. Hospital, London, United Kingdom
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  • Parts of this work have been presented at two scientific meetings (i) Eating Disorders Research Society meeting in Edinburgh, UK, September 2011 and (ii) Norwegian Eating Disorders Research Consortium at Gardermoen, Norway, December 2011.

  • Supported by Health Southeast and Oslo University Hospital, Regional Department for Eating Disorders.

Abstract

Objective:

Based on inconsistent findings in the literature, this study tested the hypothesis that “there is a season of birth bias for females with anorexia nervosa (AN).”

Method:

Females with AN, born in 1975 to 1996, were compared to females born in the same years and geographical regions by chi-square test for contingency tables with known population parameter testing for monthly deviations. Five groups were based on a priori power calculation and geographical location: Iceland, Norway and Sweden (N = 847), United Kingdom (N = 706), Oregon, USA (N = 394), Argentina and Brazil (N = 486), and Australia (N = 381).

Results:

The hypothesis was not supported in any of the groups. The associations (Cramér's V) between month of birth and the differences in distributions of births ranged from 0.05 to 0.08, none of which were statistically significant.

Discussion:

The main implication of these findings is that season of birth may not play a significant part in the aetiology of AN. © 2012 by Wiley Periodicals, Inc. (Int J Eat Disord 2013;)

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