Inattention, hyperactivity, and impulsivity in teenagers with intellectual disabilities, with and without autism

To explore inattentive, hyperactive, and impulsive behaviours in teenagers with intellectual disabilities (ID), with and without autism.

We identified teenagers with ID, with and without autism, in a single geographic area. Those with autism were matched for age, sex, and nonverbal IQ to those with ID only. We compared inattentive, hyperactive, and impulsive (IHI) behaviours in the 2 groups, along with adaptive functioning and medical circumstances. We further subdivided the autism group into those with IHI behaviours (autism IHI) and those without (autism non-IHI) and explored similarities and differences between autism subgroups.

As a group, those with autism and ID had more IHI behaviours than those with ID alone. More in the autism group met criteria for attention-deficit hyperactivity disorder and hyperkinetic syndrome. Lifetime exposure to psychotropic medication was greater in the autism group, with stimulant and antipsychotic medications predominating. However, just under one-half of those in the autism group showed no IHI behaviours. Comparison of autism IHI and autism non-IHI groups showed that those with IHI behaviours were significantly more likely to have past (but not current) exposure to stimulant medication.

One in 2 teenagers with ID and coexisting autism displayed clinically significant inattentive, hyperactive, and (or) impulsive behaviours, compared with 1 in 7 of those with ID alone. Most of the remaining teenagers with autism displayed no IHI behaviours. Our results support the need for further investigation into the prevalence and etiology of these IHI behaviours in individuals with autism.