Predicting later ADHD presentation types from early childhood autism and intellectual disability

Attention deficit/hyperactivity disorder (ADHD) and autism are both neurodevelopmental disorders associated with functional impairment in social, academic, and occupational domains.

This longitudinal study, a follow-up to the CHARGE Study (ReCHARGE), evaluated diagnosis of ADHD and its presentation type (Inattentive, Combined-Hyperactive/Impulsive), in a cohort of 8 to 20 year-olds from four developmental categories recruited at ages 2-5 years: Autism, developmental delay without autism (DD), other early concerns (OEC) or typical development (TD, controls from the general population) (n = 645). ADHD diagnosis was based on parent clinical interviews (DISC or MINI), observational methods and multiple rating scales. Multivariate Poisson log regression models were fit to estimate associations of early childhood neurodevelopment with later ADHD diagnoses. Adjusted confounding variables included child's age, sex, parental ADHD, socioeconomic indicators, and maternal prenatal conditions.

Of 645 participants, 213 (33.0%) met criteria for ADHD. Early childhood diagnosis was the strongest predictor. For Hyperactive/Impulsive or Combined presentation, relative risks (RRs [95% CI]) were 5.4 [3.0, 9.4] for autism, 4.4 [2.3, 8.4] for DD, and 3.1 [1.5, 6.1] for OEC. For Inattentive presentation, RRs were 2.6 [1.6, 4.2] for autism, 1.4 [0.7, 2.9] for DD, and 2.6 [1.4, 4.2] for OEC. For any ADHD presentation, RRs were 3.1 [2.2, 4.4] for autism, 2.4 [1.6, 3.6] for DD, and 2.4 [1.6, 3.6] for OEC.

This study reinforces the need for evaluation of ADHD and its presentation type in autistic children and other developmental delays, as these youth are at high risk for ADHD. Clinicians should assess the presence of ADHD-related challenges across development and service needs in individuals with autism and/or DD due to their high ADHD risk.