12 Intellectual disability12.4 Clinical
12.4.3 Psychological assessment and formulation of behaviour
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Written by Resident Doctor Committee · Published
Assessing intellectual and adaptive functioning
Intellectual functioning is measured with an individually administered test such as a Wechsler scale, and the score is read with its confidence interval.
Motor impairment, hearing loss, language and acute illness can all lower scores.
Adaptive functioning (conceptual, social and practical) is assessed with tools such as the Vineland, because a test score alone does not describe support needs.
Defining challenging behaviour
The Royal College of Psychiatrists defines challenging behaviour in intellectual disability by three things: its frequency, intensity or duration; its threat to quality of life or physical safety; and the restrictive, aversive or excluding responses it tends to provoke.
The definition describes impact and likely response, not cause or intent, and challenging behaviour is not a diagnosis.
Risk factors
Behaviour | Risk factors |
|---|---|
Challenging behaviour in children with intellectual disability | Communication difficulty, sensory impairment, physical illness such as epilepsy, limited coping, greater severity, male sex |
Self-injurious behaviour | Severity of intellectual disability is the most consistent marker |
Down syndrome carries comparatively low rates of challenging behaviour.
Epilepsy is linked to self-injury less consistently than severity is, and mostly because it goes with more severe disability.
Functional assessment
Functional assessment maps the immediate antecedents, the behaviour and its consequences in the setting where the behaviour occurs.
It comes before any support plan, medication or restrictive measure, because it shows what maintains the behaviour, and the person may be unable to say.
Clinicians define the behaviour observably ("strikes another person with a closed fist", not "aggression"), record an antecedent-behaviour-consequence (ABC) chart, form a hypothesis and test it by observation.
Setting events, such as poor sleep, pain, bereavement or unfamiliar staff, change how the person responds to ordinary demands.
Function | What maintains it | Example |
|---|---|---|
Escape or avoidance | Relief from an aversive demand | Screaming during personal care |
Attention | A social response | Hitting a wall when isolated |
Tangible | Getting an item or activity | Throwing furniture before a preferred programme returns |
Automatic or sensory | Consequences the behaviour itself produces | Repetitive biting in several settings |
The same behaviour can serve more than one function.
Informant scales generate hypotheses and naturalistic records show associations. Experimental functional analysis tests causal hypotheses but needs specialist skill and safeguards.
From formulation to plan
Positive behavioural support aims to improve quality of life while reducing harmful behaviour and restriction. Its plan combines proactive changes, early responses to distress and safe responses during incidents.
Functional communication training teaches an effective alternative, such as asking for a break.
Extinction means withholding the consequence that maintains the behaviour. It can cause escalation and is unsafe with severe self-injury, so it is not a default.
Fewer incidents with greater injury is not necessarily an improvement.