ObjectiveWe aimed to use real-world data to characterize the burden of psychiatric comorbidities in young people with eating disorders (EDs) relative to peers without EDs. MethodThis retrospective cohort study used a large federated multi-national network of real-time electronic health records. Our cohort consisted of 124,575 people (14,524 people receiving their index, first-ever, ED diagnosis, compared to 110,051 peers without EDs initiating antidepressants). After 1:1 propensity score matching of the two cohorts by pre-existing demographic and clinical characteristics, we used multivariable logistic regression to compute the adjusted odds ratio (aOR) of psychiatric diagnoses arising in the year following the index event (either first ED diagnosis or first antidepressant script). ResultsOver 50% of people with EDs had prior psychiatric diagnoses in the year preceding the index EDs diagnosis, with mood disorders, generalized anxiety disorder (GAD), post-traumatic stress disorder (PTSD), specific phobia (SP), attention-deficit hyperactivity disorder (ADHD), and autism spectrum disorder (ASD) being the most common. Adjusted analyses showed higher odds for mood disorders (aOR = 1.20 [95% CI = 1.14–1.26]), GAD (aOR = 1.28 [1.21–1.35]), PTSD (aOR = 1.29 [1.18–1.40]), and SP (aOR = 1.45 [1.31–1.60]) in the EDs cohort compared to antidepressant-initiating peers without EDs, although rates of ADHD and ASD were similar in both cohorts. ConclusionThis large-scale real-time analysis of administrative data illustrates a high burden of co-occurring psychiatric disorders in people with EDs.