A new study of 166,989 people found that four in ten episodes of challenging behaviour were preceded by a newly recorded physical health problem.
The study.
Millington, Rydzewska, Jahoda and colleagues at the University of Glasgow, published in BMJ Open on 3 July 2026.
Read the full published paper here
The team used English primary care records from 2009 to 2019, covering 166,989 people with intellectual disability, a mean age of 33 at study entry, and more than 850,000 person-years of follow-up. They picked eight physical health problems and sensory impairments: constipation, epilepsy, pain, visual impairment, hearing impairment, bowel incontinence, urinary incontinence and sleep problems. For each one, they looked at the twelve months either side of the date it first appeared in the record, and asked whether challenging behaviour appeared too.
The design is the point. We have known for decades that pain and behaviour travel together. What we have lacked is strong, large-scale evidence on which one arrives first. This study is the first to establish the sequence at population scale.
What they found.
Just over 21% of the cohort, 35,415 people, had challenging behaviour recorded at least once across the eleven years. Of those episodes, 40.9% were associated with a newly recorded physical health problem or sensory impairment.
All eight conditions were significantly associated with challenging behaviour after adjusting for demographics and mental health, and the associations held across every sensitivity analysis the team ran.
The four strongest:
- Bowel incontinence, hazard ratio 2.24
- Urinary incontinence, 1.93
- Constipation, 1.89
- Sleep problems, 1.74
In plain terms, a hazard ratio of 1.89 means that once constipation shows up in the record, challenging behaviour is close to twice as likely to follow.
Three of the four strongest associations are bowel and continence problems. The fourth is sleep. None of them are behavioural.
The authors’ conclusion is blunt: checking thoroughly for unrecognised physical health problems and sensory impairments should be routine in every assessment of new challenging behaviour.
What it means in practice.
This is direct evidence for something good functional assessment already assumes. Pain, continence, constipation and sleep are setting events, not background detail. Our earlier article on setting events and triggers makes the case from the practice guide. This study makes it from 850,000 person-years of data.
The practical instruction is about order of operations. When a behaviour of concern is new, or when a settled behaviour suddenly escalates, the health review comes before the plan is rewritten. Rewrite first and you can produce a technically excellent plan aimed at the wrong thing, while the person stays in pain.
It also tells you where to look and who to ask. Bowel habits, continence and sleep are the details most likely to be treated as personal care rather than clinical information, and least likely to be raised in a review meeting. The people who notice a change first are support workers and family, usually days before anyone writes anything down.
Two caveats.
Primary care almost certainly under-records challenging behaviour, so the true rate is likely higher than 21%. And more than 70% of the cohort had no record of the severity of their intellectual disability, which limits what can be said about who is most affected. Association is also not proof of cause, and the study cannot tell us whether treating the health problem resolves the behaviour.
Even with those limits, the direction of travel is hard to argue with. A large share of behaviour that gets referred to us as a behaviour problem starts as a health problem that nobody caught.
If a participant you support has behaviour that has changed recently, the cheapest and fastest thing you can do is book the GP appointment. Do that before you call us. Then call us anyway, because the two pieces of work belong together.
From the Insight PBS team to yours 🙂
Resources
Read the full article here
Read the practice guide: NDIS Quality and Safeguards Commission, Behaviour Support Assessment, including Functional Behaviour Assessment: Practice Guide (2026)
Refer to Insight Positive Behaviour Support
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