Internalizing and externalizing behaviour problems in childhood contribute to the development of anorexia and bulimia nervosa-a study comparing sister pairs.

OBJECTIVE: We wanted to clarify whether there is any clinically relevant behavioural psychopathology in patients before onset of an eating disorder (ED) compared with their healthy sisters and if there are differences in behavioural problems between the ED subtypes anorexia nervosa-restricting type (AN-R) and EDs with bulimic behaviour.
METHOD: Behavioural psychopathology was examined by parental report using the Child Behaviour Checklist retrospectively in 83 sister pairs discordant for an ED (37 with AN-R and 46 with bulimic EDs) by means of conditional logistic regression.
RESULTS: Participants who later developed an ED had significantly higher internalizing and externalizing behavioural abnormality scores before onset of the ED than their unaffected sisters. Conditional logistic regression revealed significantly higher internalizing behaviour scores in AN-R and significantly higher internalizing and externalizing scores in the bulimic disorders. DISCUSSION: Internalizing problems (anxiety, depression and somatization) preceded the development of AN, whereas both internalizing and externalizing behaviour problems (aggressive and delinquent behaviour) preceded bulimic disorders.