The 10-year trajectory of aggressive behaviours in autistic individuals.
Aggression usually fades in autism by adulthood—double your effort for kids who also show high overactivity and impulsivity.
01Research in Context
What this study did
Diemer et al. (2023) followed 345 autistic people for 10 years. They started when the kids were 8 to 12 years old. Every two years they asked parents and teachers about hitting, kicking, and tantrums.
They also tracked ADHD-type behaviors like running around and blurting out. The goal was to see who still showed aggression a decade later.
What they found
At the start, 62 out of every the kids showed some aggression. After 10 years, only 30 out of 100 still did. Most kids got better on their own.
The kids who stayed aggressive had one clear warning sign: high overactivity and impulsivity. If a child scored high on those traits early, their odds of long-term aggression doubled.
How this fits with other research
Hattier et al. (2011) looked at 4,000 people with intellectual disability. They found autism linked most to physical aggression. Diemer et al. (2023) zooms in on autism alone and shows that this aggression often fades with age. The two studies fit together: autism carries a high early risk, but the risk drops over time.
Hatzell et al. (2026) studied 8,000 autistic youth and found poor sleep raised aggression odds by a large share. C et al. did not measure sleep, so the new finding adds another red flag you can watch for.
Han et al. (2025) reviewed 25 ABA studies and saw small aggression drops after treatment. C et al. shows large natural drops without therapy. This does not clash—therapy may simply speed up what time already does.
Why it matters
You can ease up on long-term worry for most clients. Focus intense resources on the minority who show both autism and high overactivity/impulsivity. Add sleep screening, per Kalina et al., to catch extra risk.
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02At a glance
03Original abstract
BACKGROUND: Aggressive behaviours are common in people with neurodevelopmental conditions, contributing to poorer quality of life and placement breakdown. However, there is limited empirical research documenting the prevalence and persistence of aggressive behaviours in autism. In this longitudinal study, aggressive behaviours were investigated in a sample of autistic individuals over 10 years. METHODS: Caregivers of autistic individuals, both with and without intellectual disability, completed questionnaires relating to the presence of aggressive behaviours at T1 [N = 229, mean age in years 11.8, standard deviation (SD) 5.9], T2 (T1 + 3 years, N = 81, mean age in years 15.1, SD 5.9) and T3 (T1 + 10 years, N = 54, mean age in years 24.5, SD 8.1). Analyses examined the presence and persistence of aggressive behaviours and the predictive value of established correlates of aggression. RESULTS: Aggressive behaviours were common at baseline (61.6%) but only persistent in 30% of the sample over 10 years. Higher composite scores of overactivity and impulsivity at T1 were significantly associated with the persistence of aggressive behaviours at T2 (P = 0.027) and T3 (P = 0.012) with medium effect size. CONCLUSIONS: Aggressive behaviours are common in autism, but reduce with age. Behavioural correlates of attention deficit hyperactivity disorder (ADHD) predict the presence and persistence of aggressive behaviour and as such may be useful clinical indicators to direct proactive intervention resources to ameliorate aggressive behaviours.
Journal of intellectual disability research : JIDR, 2023 · doi:10.1111/jir.13004