EATING DISORDERS: AGE OF ONSET AND ITS ASSOCIATED GENETIC RISK FACTORS

Abstract

The age at which an eating disorder begins to develop has important implications for the design of services and the targeting of clinical interventions. Eating disorders have a heritability of 16-83% and a median age of onset of 18 years. However, UK-based studies on the age of onset of eating disorders and how this is influenced by genetics are lacking. We investigated the age of onset of eating disorder symptoms: binge eating (n = 6,634; 6.4% male), low weight (n = 5,570; 3.7% male), and purging behaviour (n = 6,223; 3.2% male) in two large UK research studies (n = 8,945) for participants from the UK Eating Disorders Genetics Initiative (EDGI UK) and the Genetic Links to Anxiety and Depression (GLAD) Study. Eating disorder diagnoses were algorithmderived via self-reported responses to the ED100K questionnaire and/or self-reported diagnoses via the Mental Health Disorder Questionnaire. Age of onset was assessed via selfreported age at symptom start. We regressed age of onset on polygenic scores - calculated using PRS-CS - of ADHD, anxiety, autism, educational attainment, bipolar disorder, schizophrenia, BMI, and depression. The median age of onset was younger in females than males: binge eating (18 vs. 21 years), low weight (18 vs. 20 years), and purging (16 vs. 19 years). More males reported onset older than 25 years for binge eating (41.3% vs. 18.4%), purging (29.1% vs. 10.3%), and low weight (33.2% vs. 17.6%), and onset below 10 years for low weight (2.9% vs. 0.3%). Preliminary polygenic score analyses showed that a one standard deviation increase in the educational attainment polygenic score was nominally significantly associated with an on average 0.41 years earlier onset of purging (p = 0.04) and 0.52 years earlier onset of binge eating (p = 0.01). Our study shows that eating disorders primarily begin between the ages of 16 and 25 years. Polygenic liability to higher educational attainment may be associated with earlier onset of certain eating disorder symptoms. Our results highlight the need for sufficient investment into adult clinical services, increased awareness efforts about eating disorders in adulthood, and early screening.