Adults with intellectual disabilities: prevalence, incidence and remission of aggressive behaviour and related factors.
About 1 in 4 adults with ID who show aggression will remit within two years, so plan for possible improvement, not lifelong chronicity.
01Research in Context
What this study did
S-Johnson et al. (2009) followed adults with intellectual disability for two years. They counted who showed aggression at the start, who developed new aggression, and who stopped being aggressive.
The team used surveys and service records. They did not test any treatment. They simply watched what happened over time.
What they found
At any point, about 1 in 10 adults with ID showed aggression. Over two years, only 2 in 100 developed new aggression. Nearly 3 in 10 who were aggressive at the start were no longer aggressive two years later.
In plain words, aggression often gets better, not worse.
How this fits with other research
Heo et al. (2008) looked at the same UK cohort one year earlier. They saw that half of clients were aggressive, but a small group caused most incidents. The new numbers show that even the frequent aggressors can improve.
Rojahn et al. (1994) found 11% aggression in Australia, with much higher rates in institutions. S-Johnson et al. (2009) add the hopeful news that many of those cases remit within two years.
Diemer et al. (2023) tracked autistic people for ten years and also saw big remission. Both studies tell us the same thing: plan for improvement, not lifelong trouble.
Why it matters
When you write a behaviour plan, state a clear review date. Assume the client may need less restrictive support in two years. Share the 28% remission figure with families and funders to keep goals hopeful and data-driven.
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02At a glance
03Original abstract
INTRODUCTION: Aggressive behaviours can be disabling for adults with intellectual disabilities (ID), with negative consequences for the adult, their family and paid carers. It is surprising how little research has been conducted into the epidemiology of these needs, given the impact they can have. This study investigates point prevalence, 2-year incidence and 2-year remission rates for aggressive behaviour (physically aggressive, destructive and verbally aggressive), and it investigates which factors are independently associated with aggressive behaviour. METHODS: All adults with ID - within a geographically defined area of Scotland, UK - were recruited to a longitudinal cohort. At baseline, assessments were undertaken of demography, lifestyle, supports, development, problem behaviours, disabilities and physical and mental health. These were repeated for a 2-year period. RESULTS: At baseline, the participation rate was 1023 (65.5%). After 2 years, the cohort retention was 651 adults. The point prevalence of Diagnostic Criteria for Psychiatric Disorders for Use with Adults with Learning Disabilities/Mental Retardation (DC-LD) aggressive behaviour was 9.8% (95% confidence interval = 8.0-11.8%), 2-year incidence was 1.8%, and 2-year remission rate from all types of aggressive behaviour meeting DC-LD criteria was 27.7%. The factors independently associated with aggressive behaviours were lower ability, female gender, not living with a family carer, not having Down syndrome, having attention-deficit hyperactivity disorder and having urinary incontinence. Incidence of aggressive behaviour meeting DC-LD criteria in adult life is similar to that for each of psychotic, anxiety and organic disorders. CONCLUSIONS: Aggressive behaviour is common among adults with ID, but contrary to previous suggestions, more than a quarter remit within the short to medium term. This is important knowledge for professionals as well as the person and her/his family and paid carers. There is much yet to learn about the mechanisms underpinning aetiology and maintenance of aggressive behaviour in this population, and exploratory epidemiological investigations such as this have a role to play in progressing research towards further hypothesis testing and trials to influence clinical practice, service development and policy.
Journal of intellectual disability research : JIDR, 2009 · doi:10.1111/j.1365-2788.2008.01127.x