Anxiety disorders predict fasting to control weight: A longitudinal large cohort study of adolescents.

Objective To determine whether anxiety disorders are prospectively associated with fasting for weight-loss/to avoid weight-gain, a behaviour that precedes and is typical of anorexia nervosa (AN), during adolescence. Method Participants were 2,406 female adolescents of the Avon Longitudinal Study of Parents and Children. Anxiety disorders were assessed when participants were aged 13-14 and 15-16; fasting was measured approximately 2 years after each anxiety assessment. Generalised estimating equation models examined whether anxiety disorders predicted later fasting, across the two longitudinal waves of data. To probe the moderating effect of time, data were stratified by wave and binary logistic regression analyses completed. Results Across longitudinal waves, anxiety disorder presence predicted increased risk of later fasting. Evidence from wave-stratified analyses supported a positive association between anxiety disorder presence at wave 15-16 and fasting at wave 17-18, however did not indicate an association between anxiety disorders at wave 13-14 and fasting at wave 15-16. Discussion Anxiety disorder presence in mid-late, but not early, adolescence predicted increased likelihood of later fasting. The differential association could be explained by anxiety being parent-reported at wave 13-14. Findings highlight anxiety disorder pathology as a possible eating disorder prevention target, though the nature of association observed requires clarification.