Longitudinal associations between psychotic experiences and disordered eating behaviours in adolescence: a UK population-based study

BACKGROUND: Psychotic experiences might represent non-specific markers of poor mental health in adolescence. However, only a few predominantly cross-sectional studies have tested their association with disordered eating behaviours in adolescent and adult populations. The aim of this study was to explore the association between psychotic experiences at age 13 years, and disordered eating behaviours and body-mass index (BMI) at age 18 years. METHODS: We used data from the Avon Longitudinal Study of Parents and Children, a longitudinal birth cohort based in Avon (England, UK) including mothers with an expected delivery date between April 1, 1991, and Dec 31, 1992, and their children. Psychotic experiences (such as delusions and hallucinations) and BMI were measured at clinical assessments when children were nearly aged 13 years, and data on disordered eating behaviours (ie, presence of binge eating, purging, fasting, or excessive exercise for weight loss; any of these behaviours [included to increase statistical power]; and number of behaviours [included to investigate severity]) were obtained via a postal questionnaire that used adapted questions from the Youth Risk Behaviour Surveillance System questionnaire at approximately age 18 years. For each outcome, we ran a univariable model and four multivariable models (logistic, linear [for BMI], or negative binomial [for the number of behaviours] regression), progressively adjusting for child and maternal sociodemographic, physical, and mental health characteristics (including child's sex, and maternal age, marital status, and highest academic qualification); autistic traits at age 7 years (measured with the Social and Communication Disorder Checklist); baseline BMI at age 13 years, and depressive symptoms at baseline (ie, at age 13 years when psychotic experiences were measured: childs' symptoms measured with the Moods and feelings Questionnaire, and maternal symptoms measured at 32 weeks' gestation with the Edinburgh Postnatal Depression Scale). We imputed missing outcome and covariate data. FINDINGS: Our sample included 6361 children, of whom 734 (12%) reported psychotic experiences at age 13 years. In univariable models, psychotic experiences were associated with greater odds of reporting any disordered eating behaviours (odds ratio [OR] 1·92, 95% CI 1·46–2·52; p<0·0001), and more severe symptoms (as measured by the number of disordered eating behaviours: 0·58, 0·32–0·84; p<0·0001) at age 18 years. These associations were slightly attenuated by adjustment for maternal and child characteristics (any disordered eating behaviours OR 1·82, 95% CI 1·35–2·44, p<0·0001; number of disordered eating behaviours 0·49, 95% CI 0·23–0·75, p<0·00001), autistic traits at age 7 years (any disordered eating behaviours OR 1·80, 95% CI 1·34–2·41, p<0·0001; number of disordered eating behaviours 0·48, 95% CI 0·22–0·74, p<0·00001), and BMI (any disordered-eating behaviours OR 1·83, 95% CI 1·36–2·46, p<0·0001; number of disordered-eating behaviours 0·32, 95% CI 0·06–0·57, p<0·00001) Adjusting for baseline depressive symptoms attenuated, but not removed, these associations (any disordered eating OR 1·50, 95% CI 1·10–2·03, p=0·010; more severe symptoms 0·32, 0·06–0·57, p=0·017). Psychotic experiences were also associated with greater binge eating, purging, and fasting behaviours, although some associations weakened after controlling for depressive symptoms. We noted no associations between psychotic experiences and excessive exercise or BMI in any of the models. INTERPRETATION: Our findings suggested that psychotic experiences are markers of increased risk for several disordered eating behaviours in late adolescence, possibly by indicating more severe psychopathology in early adolescence. More research investigating shared risk factors for psychotic experiences and eating disorders is warranted to elucidate shared and specific causal pathways. FUNDING: Wellcome Trust, the Royal Society, University College London Hospitals National Institute for Health Research Biomedical Research Centre, UK Medical Research Council, and the University of Bristol.