Autism Spectrum Disorder, Attention‐Deficit/Hyperactivity Disorder, Tic Disorder, and Obsessive‐Compulsive Disorder in Individuals With Eating Disorders and Their Siblings: A Nationwide Finnish Cohort Study

Objective Neurodevelopmental conditions frequently co‐occur with eating disorders (EDs). This study aimed to investigate the occurrence of attention‐deficit/hyperactivity disorder (ADHD), autism spectrum disorder (ASD), tic disorder (TD), and obsessive‐compulsive disorder (OCD) in individuals with EDs and their full and half siblings. Method Study population comprised all individuals born in Finland between 1991 and 2001 with a recorded diagnosis of the following ICD‐10 EDs ( N = 4240): anorexia nervosa (AN; F50.0/F50.1), bulimia nervosa (BN; F50.2/F50.3), and other/unspecified EDs (F50.8/F50.9). Population controls without ED ( N = 16,494) and full and half siblings of participants with ED and controls ( N = 36,301) were included. Conditional logistic regression was applied in analysis. Results Individuals with AN had increased occurrence of ASD, ADHD, and OCD compared to population controls (Odds ratios [ORs]: 6.62 [95% CI 4.21–10.39]; 3.30 [95% CI 2.33–4.69]; 10.67 [95% CI 7.07–16.10], respectively). Individuals with other/unspecified EDs had increased occurrence of ASD, ADHD, TD, and OCD (ORs: 9.06 [95% CI 5.5–14.77]; 2.78 [95% CI 1.92–4.01]; 4.68 [95% CI 1.94–11.32]; 7.64 [95% CI 4.92–11.87], respectively). The occurrence for ASD was particularly pronounced in males with other/unspecified EDs (OR 32.40 [95% CI 9.78–107.39]). Compared to full siblings of population controls, full siblings of individuals with AN had two‐fold odds for ASD and three‐fold odds for OCD; full siblings of individuals with other/unspecified EDs had 2–3‐fold odds for ASD, ADHD, TD, and OCD. Discussion Individuals with EDs have a high occurrence of neurodevelopmental conditions, also extending to their full siblings. These findings provide detailed characterization of comorbidity and the familial aggregation of these conditions.