Difficulties in assessing people with intellectual disability

Although the assessment aims to collect the same information from a person with an intellectual disability as from anyone else, the process may have to be modified.

Specific difficulties related to the intellectual disability may include the following:

Diagnostic overshadowing This occurs when psychiatric symptoms are attributed entirely to the intellectual disability. However, the only symptoms attributable to intellectual disability are the deficits in intelligence, as measured by IQ testing. In this situation, if psychiatric illness presents as challenging behaviours, the person may be incorrectly managed only in a behavioural paradigm. Intellectual distortion. A person with intellectual disability may have difficulty understanding questions regarding illness and experiences, leading to misunderstanding and incorrect answers to questions. For example, a person who says “yes” when asked if they hear voices may be answering that their hearing is OK. Questions should be asked in simple language which is appropriate to a person’s level of development. Psychosocial masking. People with intellectual disability may not have the same opportunities and experiences as the general population. Where symptoms seem simple or unconvincing they should be considered in the context of a person’s developmental level. For instance, mania may present with the belief of having a job as a bus driver and paranoid delusions may present with thoughts that people are telling lies about them. Cognitive disintegration. People with intellectual disability may show bizarre behaviour and disruption of their thought processes at times of stress, which can mimic symptoms of mental illness. Baseline exaggeration Pre-existing difficulties with thoughts, actions and behaviours may be exaggerated at times of stress and upset. For example, the only sign of a depression in someone unable to talk may be an increased frequency of self-harm. Cloak of normality People with intellectual disability are often subjected to stigma and prejudice. For some it is important to present as ‘normal’ and this can lead to all symptoms or difficulties being denied. Communication The process of completing the psychiatric interview and mental state examination may not be possible. Assessment may have to rely on observation and collateral history regarding a person’s usual presentation and any changes. Questions should be simply asked in short sentences. The person can be asked to explain the question in their own words if there is doubt as to their understanding. Open questions allowing the person to answer in their own words are helpful. Suggestibility If a question is too difficult, or the person wishes to please their interviewer then asking leading questions (e.g. you’re feeling sad, aren’t you?) can lead to meaningless answers. Open questions (e.g. how do you feel today?) should be used to direct questions. If need be, more specific questions can be used to clarify (e.g. do you feel happy?). Acquiescence People with intellectual disability may be easily talked out of delusional beliefs or other psychiatric symptoms if they wish to please the clinician (e.g. ‘you aren’t really hearing voices, are you?’). Care should be taken in how questions are asked. Perseveration and echolalia. Some people with intellectual disability and also developmental disability can repeat questions as answers, or repeat the last thing said to them. It is important to ask questions in different ways to ensure that the answer provided is meaningful rather than repetition.