From Toddlerhood to Adolescence: Which Characteristics Among Toddlers with Autism Spectrum Disorder Predict Adolescent Attention Deficit/Hyperactivity Symptom Severity? A Long-Term Follow-Up Study.

The team tracked the same kids with autism from toddlerhood to age 13-14. They looked at how two early signs—repetitive behaviors and daily living skills—linked to later ADHD problems.

Parents filled out the same checklists when the kids were 2-3 and again in middle school. No new treatment was given; the study just watched what happened.

Toddlers who showed lots of hand-flapping, lining up toys, or other repeated actions grew into teens with worse inattention and hyperactivity. Kids who needed more help with dressing, eating, or toilet skills at two also had sharper ADHD spikes later.

Iversen et al. (2021) pooled almost 3,000 kids and found the same bridge: more repetitive actions go hand-in-hand with weaker executive functions like shifting attention or waiting. The new study shows that bridge can be seen years earlier and predicts ADHD, not just day-to-day flexibility.

Uljarević et al. (2017) showed that late motor milestones forecast higher repetitive behaviors. Pitchford et al. (2019) take the next step: those early repetitive behaviors themselves forecast ADHD in adolescence, forming a timeline clinicians can watch.

Krakowski et al. (2026) report that poor executive function in 3-year-olds with autism already drags down adaptive scores. The current paper agrees and adds that low adaptive scores keep predicting trouble—this time in the form of ADHD symptoms—ten years out.

You can flag high-risk cases during intake. If a toddler shows many repetitive actions and needs help with basic self-care, plan to monitor and maybe boost executive-function and adaptive-skills programs early. Tracking these two simple metrics gives you a heads-up that hyperactivity or attention problems may surge in middle school, so you can adjust behavior plans before academic and social demands explode.