Prevalence estimates of eating disorders range from 3-21% in adolescent and young adult women (Field et al, 2012; Machado et al, 2007; Smink et al, 2012). The consequences of eating disorders are devastating, including a detrimental impact on the sufferer’s daily, social, and academic functioning, as well as increased mortality. Thus, identifying the risk factors behind the development of eating disorders is a key avenue for research in this area.

Previous studies suggest that one such risk factor could be the presence of an eating disorder in a family member (e.g. Steinhausen et al, 2015).

New research recently published in Acta Psychiatrica Scandinavica, led by Mental Elf contributor Dr Helen Bould (Bould et al, 2015), sought to complement the findings of these previous studies by investigating the relationship between eating disorders in parents and offspring in a large multi-generation register-based Swedish sample.

Methods

The sample in this study consisted of 158,697 children aged 12-24 years old who were ever resident in Stockholm County between 2001 and 2007 (as identified through the Register of Total Population, provided by Statistics Sweden). To be included in the sample, the children had to have turned 12 years of age before the 31 December 2007.

Diagnoses of eating disorders in the children and in their biological parents were identified using participants’ national registration numbers and record linkage to national and regional health data, such as the Swedish National Patient Register. Only diagnoses made after the age of 12 in either children or parents were included in the analyses. In addition, only diagnoses in parents made before their subject child turned 10 years were included, so as to minimise the possibility of reverse causality.

The presence of any type of eating disorder in participants, including anorexia nervosa, bulimia nervosa, or an eating disorder not otherwise specified (EDNOS), was determined by whether participants had been given an indicative ICD-10 code or DSM-IV code by a specialist clinician, or if they had attended a specialist eating disorder clinic.

Results

• The presence of a diagnosed eating disorder was identified in:
  • 775 parents (0.5%)
  • 2,131 children (1.3%)
• Controlling for maternal age at the child’s birth, parental occupational class, maternal level of higher education, family type and number of siblings, the authors found that rates of eating disorders were higher:
  • when the child’s mother or father had been diagnosed with an eating disorder,
  • or when the child’s mother had been diagnosed with an eating disorder.
  • These findings held in the overall sample and in male and female children separately.
• Evidence was particularly strong for the relationship between:
  • the diagnosis of an eating disorder in either parent and the diagnosis of an eating disorder in their female child,
  • and the diagnosis of an eating disorder in the mother and the diagnosis of an eating disorder in their female child.

Conclusions

This longitudinal study examined the relationship between diagnoses of eating disorders in parents and offspring in a large, population-based sample. The data collection techniques used in this study served to minimise issues of sample attrition, missing data, and participant recall bias.

The results of this study show that rates of diagnosed eating disorders are two-fold higher in children of parents with diagnoses of eating disorders, which supports previous research indicating the potential familial transmission of eating disorders.

Limitations

As the authors acknowledge, underestimation of the prevalence of eating disorders in this study could have resulted from the following factors:

• Changes over time in the routine reporting of diagnoses to the central registers in Sweden.
• The presence of an eating disorder in participants was defined in terms of a clinical diagnosis or presentation at a specialist eating disorder clinic. Studies indicate that in fact relatively small proportions of individuals with eating disorders actually seek treatment (e.g. Solmi et al, 2014).

Underestimation of the prevalence of eating disorders could also have stemmed from the varying follow-up periods for the children in the study, in that some children may have turned 12 years old (point of entry to the study) close to the end of the study follow-up period, whereas others may have turned 12 long before the end of the study follow-up period.

As the authors also note, the small numbers of male children and paternal eating disorder cases limited the meaningfulness of any statistical inferences regarding male participants.

Implications

The findings of this study crucially establish parental diagnosis of an eating disorder as a risk factor for the diagnosis of an eating disorder in offspring, particularly in female offspring. The authors appropriately conclude that this has strong implications for targeted preventive initiatives.

I also wonder about the extent of this risk factor, in terms of how many generations in families experience eating disorders. Future longitudinal research could potentially examine the prevalence of eating disorders in the children’s parents and grandparents, as well as in the children’s own offspring. Finding ways to ‘break the chain’ would clearly be of the utmost importance for clinicians and researchers in this area.

Ultimately, this can only be achieved through exploration of the risk mechanisms underlying this relationship, which, as the authors state, is “the main unanswered question” of this study. Potential mechanisms underlying the relationship between parental and child eating disorders could lie in the variation of child exposure to parental eating disorders, genetic influences (e.g. Bulik et al, 2006), and/or ‘learned behaviour’. Investigation of these risk mechanisms is arguably another logical and integral step for further research in this area.

Caption:

Links

Primary paper

Bould H, Sovio U, Koupil I, Dalman C, Micali N, Lewis G, Magnusson C. (2015) Do eating disorders in parents predict eating disorders in children? Evidence from a Swedish cohort. Acta Psychiatrica Scandinavica, 132, 51 – 59. [PubMed abstract]

Other references

Bulik CM, Reba L, Siega-Riz AM, Reichborn-Kjennerud T. (2005) Anorexia nervosa: Definition, epidemiology, and cycle of risk (PDF). International Journal of Eating Disorders, 37 (Suppl), S2 – S9; discussion S20 – S21.

Field AE, Sonneville KR, Micali N, Crosby RD, Swanson SA, Laird NM, … Horton NJ. (2012) Prospective association of common eating disorders and adverse outcomes (PDF). Pediatrics, 130, 289 – 295.

Machado PP, Machado BC, Goncalves S, Hoek HW. (2007) The prevalence of eating disorders not otherwise specified. International Journal of Eating Disorders, 40, 212 – 217. [PubMed abstract]

Smink FR, van Hoeken D, Hoek HW. (2012) Epidemiology of eating disorders: Incidence, prevalence and mortality rates. Current Psychiatry Reports, 14, 406 – 414.

Solmi F, Hatch SL, Hotopf M, Treasure J, Micali N. (2014) Prevalence and correlates of disordered eating in a general population sample: The South East London Community Health (SELCoH) study (PDF). Social Psychiatry and Psychiatric Epidemiology, 49, 1335 – 1346.

Statistics Sweden website, last accessed 28 Sep 2015.

Steinhausen HC, Jakobsen H, Helenius D, Munk-Jorgensen P, Strober M. (2015). A nation-wide study of the family aggregation and risk factors in anorexia nervosa over three generations (PDF). International Journal of Eating Disorders, 48, 1 – 8.