IDD-MH Prescriber Guidelines

Challenges in Assessing Persons with ID

 Joan B. Beasley, PhD, and Dan Baker, PhD

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How to Address

Diagnostic overshadowing

Professionals wrongly assume that symptoms are attributed to one diagnosis and do not take other factors into consideration

Sometimes clinicians explain away sudden self-injury, saying “Don’t all people with autism slap themselves?”  

Not all people with ASD express themselves through SIB. Consider the last time the patient was doing “well” what did they look like? Regardless of frequency of self-injury, SIB is a sign of distress and must be examined as a symptom, bio medical issues ruled out.

Baseline exaggeration

Challenging behavior that exists at a low rate and low intensity may increase dramatically when one experiences stress or a mental health condition

SIB has always been present at low levels throughout a person’s life but has increased dramatically in the last 3-6 mo.

A person with ASD may express a variety of issues through the same challenging behavior. If attributed to their ASD, these will be missed. Increase in intensity and duration is likely a sign of medical or mental health acuity. Pain and discomfort are often present. Consider dental and primary medical conditions. Symptoms of mania, depression, anxiety can all be expressed through baseline exaggeration.

Intellectual distortion

Difficulty for a person to determine if what they are experiencing is reality

When asked the question, “Do you hear voices?” a person might answer yes.

Interview the patient using plain language. Ask the patient to elaborate in their own words, explore beyond yes or no answers.

Psychosocial masking

Misunderstanding of developmental delay


A delusion of being the chief of police may be mistaken for a harmless fantasy

An imaginary friend may be mistaken for a delusion

A more detailed account of the delusional presentation is required, including its disruption in vegetative function. Consider trauma and possible triggers/instigators

Cognitive disintegration

Response to stress that is part of the human condition but can be more pronounced for people with IDD. People may dramatically decompensate under stress

A person recently lost a family member is bereaved. They used to do their own laundry and make small meals, but their ability to navigate the completion of daily living activities is greatly compromised.

This can also include “tantrums”, where the person’s executive functioning/coping is severely compromised. Like many issues, understanding the context and pattern of medical issues, negative events, loss of skills, is key. Knowing baseline skills and what transpired after (when the person was doing well) is key.


Reference: Hurley, A.D. (1996). Identifying psychiatric disorders in persons with mental retardation: A model illustrated by depression in Down syndrome. Journal of Rehabilitation 15, 6-31.