Familial Transmission of Risk for Bulimia and Anorexia Nervosa

In what may be the largest case-control family study to date of the genetics of eating disorders, researchers have established familial links to the risk of developing anorexia nervosa and bulimia nervosa (Am J Psychiatry 2000; 157:393).

The subjects included 3 groups of Caucasian female probands (the individual with the disorder is called a proband) 18 to 28 years of age. The groups included 152 women with pure restricting subtype anorexia nervosa, 171 women with pure bulimia nervosa, and 181 women with no lifetime axis I psychiatric illness (controls). Information was sought on lifetime psychiatric histories of all first-degree relatives 12 years of age or older.

The 3 groups had a total of 1831 living or deceased relatives on whom information was obtained. Of the 1727 living relatives, 1561, or 90.4%, were interviewed. Ninety-five relatives, all female, were diagnosed with either a full or partial eating disorder

Diagnostic criteria for partial anorexia nervosa

The researchers stipulated that a diagnosis of partial anorexia nervosa required, in a person of normal body weight, unequivocal anxiety about body weight that was judged to be extreme or irrational and the concurrent presence, for at least 3 months, of at least 2 of the following characteristics:

(1) distraction from daily chores or life demands because of anxiety about weight;

(2) a seemingly unshakable conviction of being overweight and the belief that losing weight could reduce discomfort or frequent monitoring of weight, driven by anxiety about weight or shape; and

(3) marked distress brought on by eating meals believed to be of normal or below-normal size, or composed of foods the subject believed were “unsafe,” or extreme distress upon minor fluctuations in body weight, extreme or rigid adherence to exercise regimens, or use of laxatives, diuretics, or anorexic agents.

Familial risk factors

The study offered new evidence of the importance of familial factors in the risk for anorexia nervosa and bulimia nervosa. Whereas anorexia nervosa was rare in families of the comparison subjects, full and partial syndromes of anorexia nervosa aggregated among female relatives of both anorectic and bulimic probands.

The age-specific risk for anorexia nervosa in female relatives of probands with anorexia nervosa was 11.4 times as high as the risk in relatives of normal probands. By comparison, the risk of bulimia nervosa was 3.7 times as high among female relatives of probands with bulimia nervosa as in relatives of normal subjects. The age-corrected risk for bulimia nervosa was 3.5 times as high among relatives of anorexic probands as among relatives of comparison probands, whereas the risk for anorexia nervosa was 12.1 times as high among relatives of bulimic probands. Further, milder forms of anorexia nervosa and bulimia nervosa also showed a tendency to run in families. The authors noted that the cross-transmission in families suggests a common, or shared, family diathesis.