The association between severity of intellectual disability and psychiatric symptomatology.
Psychiatric labels lose power as ID deepens—switch to behavioural and environmental assessment.
01Research in Context
What this study did
The team gave rating scales to carers of adults with intellectual disability. They split the adults into three groups: moderate, severe, and profound ID. Then they counted how many psychiatric symptoms each group showed. They also recorded who was taking psychotropic medicine.
What they found
Adults with moderate ID had the most psychiatric symptoms. Adults with profound ID had the fewest. Drug use was the same across all three groups. In short, the more severe the ID, the less useful a mental-illness label became.
How this fits with other research
Keintz et al. (2011) asked the same question seven years later and got the same curve: profound ID scored lower on behaviour checklists than severe ID. The finding held.
Poppes et al. (2010) looked deeper into the profound group. They found that 82 % showed self-hitting or rocking every day, yet staff still rated the behaviour as “mild.” The two studies seem opposite until you see the gap: behaviour can be frequent yet still called low-impact.
van Timmeren et al. (2016) moved the field forward. They showed that dimensional mood scores predict outcomes better than classic illness labels. Their work supports the 2004 warning: ditch the DSM box once ID severity rises.
Why it matters
Stop hunting for a hidden psychiatric diagnosis when your client has profound ID. The 2004 curve says the label adds little. Pair your functional assessment with sensory, communication, and environmental data instead. You will write better behaviour plans and cut needless meds.
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02At a glance
03Original abstract
BACKGROUND: Mental illness is more prevalent in people with intellectual disabilities (ID) than in the normal population. The association between mental illness and severity of ID is also of importance in the understanding and treatment of maladaptive and challenging behaviours. The aim of this study was to investigate the association between severity of ID and prevalence of mental illness. METHODS: Using the Mini PAS-ADD, an instrument designed to identify psychiatric symptoms in people with ID, informants were interviewed about the presence of symptoms in 96 participants with moderate, severe and profound ID, and asked about the use of psychotropic medication. RESULTS: Mental illness, particularly anxiety, depression and psychosis, was far more prevalent in participants with moderate ID than in people with severe and profound ID. The use of psychotropic medication was not significantly different between the groups. CONCLUSIONS: The prevalence of psychiatric illness decreases with severity of ID. The usefulness of psychiatric illness models, in explaining maladaptive and challenging behaviours, also decreases with severity of ID. Drug treatment may become more complicated, and behavioural and environmental interventions may become relatively more important, as severity of ID increases.
Journal of intellectual disability research : JIDR, 2004 · doi:10.1111/j.1365-2788.2004.00624.x