Familial aggregation refers to occurrence of a given trait shared by members of a family. Two groups of researchers have recently published papers that expand our knowledge about the familial nature of eating disorders.
Swedish research team members led by Dr. H. Bould used a subset of the Stockholm Youth Cohort born between 1984 and 1995 (286,232 individuals) to investigate whether parental eating disorders in parents predict the development of eating disorders in their children. A subset of these youths had a parent with an eating disorder, and the authors searched for any diagnosis of an eating disorder in their offspring. The diagnosis had to be made by a specialist clinician or inferred from an appointment at a specialist eating disorder clinic (Acta Psychiatr Scand. 2015; January 9. doi: 10.1111/acps.12389 [Epub ahead of print]. A final study sample of 158,697 (55.4%) cases were included.
The results showed that a parental eating disorder (affecting either parent) was associated with eating disorders in their female children. Due to the small number of cases, no conclusions could be drawn about risk for male children.
Nationwide study of family aggregation and risk of AN over three generations
A second study also showed evidence of family aggregation and specific risk for AN. In a nationwide population sample, Hans-Christoph Steinhausen, MD, PhD, Alborg University Hospital, Alborg Denmark, and Swiss and Danish investigators conducted a study that explored how often AN and co-morbid disorders occurred in affected families compared with control families (In J Eat Disord. 2015; 48:1). Cases and controls were observed for long periods—the maximum was 40 years. For the case-probands, the mean observation time was 15.35 years. The data set contained 2,370 case-probands with AN identified through the Danish Psychiatric Central Research Registry and 7,035 controls.
The main finding of this second study was that AN occurred more often in relatives of case probands than in controls. AN was not seen in fathers of ill probands.
Taken together, these two papers expand what we know about eating disorders in families. They are both broadly representative cohorts (one, in fact, is a nationwide study). Critically, they are longitudinal, which helps to eliminate recall biases.
Eating Disorders Review