The age related prevalence of aggression and self-injury in persons with an intellectual disability: a review.

Bøttcher et al. (2013) pooled every paper they could find on age and challenging behavior in people with intellectual disability.

They asked one question: does hitting, biting, or head-banging happen more often as these adults get older?

The review covered all ages, not just kids.

Aggression and self-injury climb with age.

The peak is in mid-adulthood, not childhood.

After that, the behaviors slowly drop off again.

Burack et al. (2004) extends the picture. They showed that teens and young adults with both autism and severe ID already carry five times more psychiatric and behavior disorders than peers with ID alone.

Ghaziuddin (1997) adds the late-life view. His case series found adults over 75 show high medical morbidity and little challenging behavior, matching the downward slope Louise saw after mid-life.

Hutzler et al. (2010) and Whitehouse et al. (2014) look at the same ID group but focus on physical activity. Their reviews say exercise and peer modeling improve well-being, giving you a proactive tool while behaviors are still rising.

You now have a timeline. Expect more aggression and self-injury between 30 and 50, especially if autism is also in the mix. Start functional assessments and skill-building earlier, not later. Add exercise programs with peer models; they are low-cost and may delay the mid-life peak. Track medical issues as clients age past 65, because behavior often fades while health risks grow.