LAUSR

OBJECTIVE To evaluate the prevalence and major comorbidities of ADHD, using different operational definitions, in a newly available national data set and to test the utility of operational definitions against genetic and cognitive correlates. METHOD The U.S. Adolescent Behavior Cognition Development (ABCD) study enrolled 11,878 children aged 9-10 years at baseline. ADHD prevalence, comorbidity, and association with polygenic risk score (PRS) and laboratory-assessed executive functions were calculated at four thresholds of ADHD phenotype restrictiveness. Bias from missingness, sampling, and nesting were addressed statistically. RESULTS Prevalence of current ADHD for 9-10 year old children was 3.53% (95% CI: 3.14-3.92%) when computerized Kiddie Schedule for Affective Disorders and Schizophrenia (KSADS-COMP) and parent and teacher ratings were required to converge. Of ADHD cases so defined, 70% had a comorbid psychiatric disorder. After control for overlapping comorbidity, and ruling out for psychosis or low IQ, 30.9% (95% CI: 25.7-36.7%) had a comorbid disruptive behavior disorder, 27.4% (95% CI: 22.3-33.1%) an anxiety or fear disorder, and 2.1% (95% CI: 1.2%-3.8%) a mood disorder. Children in the top decile of polygenic load incurred a 63% increased chance of having ADHD versus the bottom half of polygenic load (p<.01)-an effect only detected with a stringent phenotype definition. Dimensional latent variables for irritability, externalizing, and ADHD yielded convergent results for cognitive correlates. CONCLUSION This fresh estimate of national prevalence in the United States suggests that the DSM-5 definition requiring multiple informants yields a prevalence of about 3.5%. Results may inform further ADHD studies in the ABCD sample.