Medical Assessment Considerations for Patients with Intellectual and Developmental Disabilities

I. Leslie Rubin, MD & Lauren R. Charlot, PhD, LICSW

Editors’ Note: Some content in this chapter is intentionally repeated from the early chapter on Health Promotion because it is critically important to the mental healthcare of people with intellectual and developmental disabilities (IDD). Accurate and comprehensive assessment for people with IDD requires attention to communication, setting, and the thorough gathering of medical and behavioral history. Reiterating these elements emphasizes their central role in ensuring high-quality care and accurate diagnostic and treatment formulation.

Overview

For the mental health provider who cares for the behavioral and mental health needs of people with intellectual and developmental disabilities (IDD), the challenges are manifold.¹

• Clinicians may not have the training or tools to engage people with IDD in reporting their symptoms and experiences. While resources are somewhat available, adaptive strategies are not typically included in clinician training.
• People with IDD may have difficulty with expressive language and have difficulty describing their symptoms using traditional communication methods, which makes it difficult to explore the important medical, emotional, social, or environmental history, which are the cornerstones of a clinical diagnosis.
• For the people who are unable to articulate symptoms of discomfort or pain, behavioral expressions of the symptoms may not necessarily reflect the actual cause of discomfort or pain. For example, some people who are on the autism spectrum may have dramatic emotional reactions that are out of proportion to symptomatology, or, even in the presence of significant pain, there may be minimal expression of the symptoms.
• People with IDD may present to the healthcare provider accompanied by a family member or a familiar supporter, or, in some instances, they may be accompanied by an escort with limited or no prior experience with the patient. If the third party is a family member or familiar supporter, then interpretations of symptomatology and the provision of a reasonable history will help to make a diagnosis; however, if the third party is an unfamiliar escort, then the history is minimal or non-existent, making the assessment and diagnosis of the condition more challenging. It is important to note that even family members may not necessarily serve as accurate proxies on behalf of the person with IDD.
• To complicate the challenge of the assessment, the person with IDD may be fearful of the clinician and uncooperative for the physical examination, or become defensive and aggressive, making it more difficult to confirm clinical suspicions or explore physical conditions that may be causing the symptoms.

With these considerations in mind, it is critically important for the healthcare provider to be aware of the limitations in making a diagnosis based on history and behavior.¹ It is important for the clinician who is evaluating concerns about discomfort or pain through behavioral manifestations to consider a differential diagnosis that includes medical conditions, possible mental health considerations, as well as social and environmental factors. 

There are additional elements required in obtaining a useful clinical history:¹ 

• It is critical to provide as comfortable a setting as possible, in a quiet location with minimal distractions. It is also important to speak softly, move slowly, and provide a reasonable amount of time for the person with IDD to adapt to the environment and the people in it. When conducting a physical examination, it is important to say what you are going to do before you do it, to give the person time to prepare, comply, and cooperate.
• Be aware of the person’s communication style and mannerisms that help in gathering important historical information, and in conducting the physical examination to provide additional information for the diagnostic assessment.
• Examine and explore the person’s patterns of behavior relating to daily health and routine. This includes eating habits, sleeping habits, bowel and bladder routines, exercise routines, work routines, social routines, as well as habits such as smoking or drinking alcohol or other emotional outlets.
• Inquire about any changes that may have taken place in any of the daily routines, as well as changes in the person’s weight and vital signs. It is also strongly advisable to obtain a history of living circumstances, past and present, with attention to any changes that may have taken place in the recent past.
• Review past medical history which includes all past physical health related episodes, previous diagnoses, notes from specialty health care providers, as well as histories of previous emergency room visits, hospitalizations or surgeries; history of allergies; past medications; medication responses and reactions; current medications, including the duration of the regimen, with exploration of possible drug interactions; and past history of behavioral responses to medical, social, and environmental experiences.

Answers to these questions help to create a comprehensive multidimensional picture of the individual and the complex interplay between physical, physiological, psychological, social, emotional, and environmental factors. It also helps guide an assessment of the current clinical challenge to determine whether further evaluations or referrals are necessary, and ensures a more accurate diagnosis, more appropriate treatment and therapeutic recommendations, and favorable outcomes.

Etiological Considerations^1,2

Important to the clinical assessment of a person with IDD is the etiology of the condition. Different etiologies that include prenatal, perinatal, and postnatal causes, as well as genotype and phenotype, will explain physical characteristics, behavioral patterns, and in some cases, associated organ system disorders. An etiological framework of developmental disabilities from neuromotor, neurocognitive, and neurobehavioral perspectives can help the clinician conceptualize the underlying central nervous system disorder. Varied etiologies can determine the clinical manifestations and shape understanding, diagnosis, and management.

Figure 1: Developmental Disabilities Causes and Consequences

Knowledge of the etiological diagnosis is an invaluable aspect in the clinical assessment of a person with IDD. Three illustrative examples will be offered: people on the autism spectrum who tend to have less obvious physical or medical co-morbidities; people with predominantly motor disabilities such as cerebral palsy, who are likely to have more complex physical and medical co-morbidities; and people with an underlying congenital chromosomal or non-chromosomal syndromes, such as Down syndrome, which each have their own unique physical characteristics, underlying organ system disorders, and at times, patterns of behavior. It is important to note that within each of these categories there are variations and variabilities as well as commonalities. In each, the level of cognitive ability and ability to communicate vary, and there may be overlapping diagnoses. So, a person with cerebral palsy or Down syndrome may also have an autism spectrum disorder. Similarly, the underlying central nervous system disorder often plays out with similar physical and mental health concerns as are experienced by the general population but with greater likelihood and often to a greater degree. Thus, each person with IDD should be seen as a unique individual with some likely physical and behavioral patterns that help to establish an accurate physical or mental health diagnosis

Autism Spectrum Disorders (ASD)

People with autism spectrum disorders (ASD) have underlying difficulties with communication, interaction, and socialization, and can become easily frustrated in being unable to express themselves or make a request. This can lead to distress which may manifest in a fright, flight, or fight response with profound consequences. They are also more likely to have exaggerated reactions to sensory stimuli that may not bother anyone else. Their overreactions in these two examples may be interpreted in terms of behavioral pathology or a mental health disorder, so careful attention needs to be paid to the circumstances of any dramatic presentation.³ 

People with ASD are also more likely to have repetitive mannerisms and behaviors, tic disorders, and even Tourette syndrome and seizure disorders. Therefore, unusual patterns of action or movement need to be analyzed for more accurate characterization and thus inform the approach to management. People with ASD also have psychiatric comorbidities such as sleep disorders, ADHD, anxiety, OCD, depression, bipolar disorder, episodic dyscontrol syndrome, and psychoses. These need to be factored into the diagnostic consideration and managed accordingly.

Because people with ASD have limited communication skills, a tendency for unusual (over or under) sensitivity to sensory stimuli and may have possible significant emotional overreactions, and their physical symptoms are more likely to manifest in behavioral reactions. This is best known and documented with gastrointestinal disorders such as gastroesophageal reflux (GERD) and constipation.⁴ Because people with ASD and/or IDD may be unable to describe their symptoms accurately, discomfort or pain may be expressed with a variety of behavioral symptoms such as withdrawal (especially with constipation), or frustration manifesting in emotional or behavioral challenges. 

Both medical conditions can be easily missed because the symptoms may be in the form of non-specific emotional or behavioral presentations without any clinically observable physical or medical signs or symptoms. The challenge to the clinician with these underlying medical conditions, is that it may be difficult to get a complete or comprehensive history or even perform a thorough examination to determine the diagnosis, and even so, it may be difficult to diagnose clinically because there may be no obvious findings. In these situations, it becomes imperative to develop an approach that is systematic in exploring changes in the environment and in reviewing the possible non-visible conditions that might explain physical pain or discomfort that may be present, such as headache, dental pain, or abdominal pain. It is therefore critical to explore the possible physical conditions before attributing the behaviors to a psychological or psychiatric cause.

Cerebral Palsy (CP)^5-8

Cerebral palsy (CP) is defined as a disorder of movement and posture as a result of a fixed insult to the developing brain that occurred before, during, or soon after birth. The diagnosis of CP is based on the presence of motor characteristics with significant functional implications; however, the reality is that the central nervous system (CNS) insults are often diffused and involve other functional elements. The CDC reports that for people with CP, more than 40% have intellectual disability, 35% have epilepsy, and more than 15% have vision impairment.¹ The association between ASD and CP has been well documented. 

Overall, the prevalence of associated mental health disorders in people with CP is higher than the general population, especially as people age. When evaluating a person with CP, it is important to be aware of emotional and social factors in the person’s life as these may result in frustration, anger, anxiety, or depression. Furthermore, care providers who are family members may also be stressed because of the physical demands of supporting a person with physical limitations in activities of daily living as well as other related stresses that may be emotional, social, and financial difficulty. 

People with CP are more likely to have complex medical problems too. There is obvious musculoskeletal involvement with limitations in movement and changes in posture, associated with changes in muscle tone, especially spasticity, which may involve muscle spasms or tremors and clonus. They are also more likely to have seizures which may be expressed in a variety of different forms and can be confused with behavior disorders. Seizure medication prescribed to manage seizures may have a variety of different side effects ranging from gastrointestinal disorders, metabolic and hematological disorders, and often changes in behavior. They can also cause things like headaches and dizziness that can manifest in behavior challenges (due to functional communication limitations). People with CP are also more likely to have other organ system disorders and ailments that do occur in the general population, but with greater frequency and intensity, most notably gastrointestinal disorders, such as GERD, and constipation. 

It is critical for the health care provider to be aware of common conditions; to make specific inquiries of the patient, family members, and caregivers; and if there is an index of suspicion, refer the patient for an x-ray of the abdomen to rule out constipation, or to a gastroenterologist for further evaluation. It is quite clinically acceptable to prescribe laxatives if constipation is suspected and monitor the outcome, or to prescribe an anti-reflux mediation or antacid if GERD is suspected. These ‘first aid’ measures will hopefully provide some relief to the patient with a reduction in symptoms with consequent improvement in presentation and assist the clinician in making a more accurate diagnosis while waiting for consultations with a gastroenterologist, or other specialty providers.

Diagnostic Syndromes

People who have a chromosomal anomaly (genotype) or a non-chromosomal syndrome are likely to have distinctive physical characteristics (physical phenotype), characteristic organ system involvement, and often a behavioral phenotype. For reviews of a compendium of genotypes and phenotypes it is helpful to consult the latest edition of Smith’s Recognizable Patterns of Human Malformation,⁹ first published in 1969 and now in its 8th edition. This book offers a compilation of chromosomal and non-chromosomal disorders along with physical descriptions and associated organ system complications and medical comorbidities. In addition, the reader is referred to the text Health Care for People with Intellectual and Developmental Disabilities Across the Lifespan.² This text contains in-depth information on a select group of common conditions with more detail on the medical complications of each of the syndromes discussed. It also has a comprehensive review of all physical and mental health related considerations as well as addressing familial, educational, and social aspects of health and health care, and systems of health care delivery.  

Down syndrome^9,10 is the most common and well-known genotype associated with IDD and has a variety of associated organ system conditions that may manifest at birth. Examples include congenital anomalies such as congenital heart lesions, and gastrointestinal anomalies such as duodenal stenosis or Hirschsprung’s. Although congenital lesions are dramatic and require urgent care including surgery, other more common conditions associated with Down syndrome pose clinical challenges to primary care and mental health care providers. 

In these situations, the clinician should become familiar with the range and variety of medical conditions. Visual and hearing impairments and obstructive sleep apnea are common, so it is important to be aware of these possibilities and refer them for evaluation when suspected. Like other causes of IDD, a person with Down syndrome may have GERD and constipation which need evaluation. In addition, hormonal disorders, most notably hypothyroidism, may manifest as loss of energy or lethargy. For this reason, regular screening for hypothyroidism is recommended. Musculoskeletal disorders are also more common in people with Down syndrome, including hypotonia with ligamentous laxity and tendency for dislocations and subluxations. Of particular concern is the tendency for atlanto-axial subluxation – that is cervical vertebrae C1 on C2, which may manifest in an inability to walk which may be misinterpreted as willfulness (or less strengths-based, as non-compliance). People with Down syndrome are more likely to have ADHD and ASD than the general population, so it is important that the clinician is aware of these conditions and looks beyond the Down syndrome diagnosis for assessment of challenging behaviors. Like everyone else, people with Down syndrome may have mental health conditions or have adverse life experiences that shape their presentation.¹¹ For the clinician, it is important to be aware that people with Down syndrome are more likely to develop Alzheimer’s dementia at an earlier age than the general population. 

Medication Adverse Effects

An important and serious consideration for the clinician is that people with IDD are more likely to have associated neurological and medical conditions that require medication management, and that all medications have potential side effects. These side effects may have metabolic, hematological, organ system disturbances, or CNS disturbances that manifest in neuromotor, neurobehavioral, or neuropsychiatric concerns particularly if taken long term. Therefore, medication should be thoroughly reviewed on a regular basis and, when assessing a person for changes in behavior, it is important to determine the onset of the symptoms in relation to changes in medication administration. It is critically important to be sure that the person is indeed taking their medication as prescribed, that is, knowing that it is given and that it is swallowed. One further consideration about medication is that there may be a difference in effect between the brand medication and different generic forms which should be discussed with the pharmacy if suspected. 

Conclusion

For any clinician who provides physical or mental health services for people with IDD, be it a primary care provider or specialty provider, it is important to be aware of the physical health conditions that may manifest as mental health or behavior disorders. This chapter provides an overview for the reader to become familiar with the common conditions that are often missed because people with IDD may not be able to describe their symptoms accurately or clinicians do not know how to elicit important and relevant clinical information. There are many conditions that are not obvious on physical examination that should be considered, most commonly, the gastrointestinal disorders of GERD and constipation.

The important message for the clinician is to: 

• Take as good a history as possible from the patient, as well as from family members, and other care providers because the more perspectives, the easier it is to make a diagnosis.
• Get assistance with the clinical interview by someone who knows how to elicit accurate responses from the patient.
• Ask informants to describe as accurately as possible what they saw and heard, rather than offer opinions, hypotheses or even diagnoses. It is also helpful to enquire about a timeline that begins from baseline wellness to changes in presentation (medication changes, altered eating, drinking, sleeping, weight, etc.) to understand potential contributing factors might be helpful.
• Review the medical and psychiatric history as well as the environmental and social history
• Be aware of the medical conditions that may present with behavior changes or challenges.
• Conduct a broader based examination than would be usual for patients looking specifically for common causes of irritability and aggression.
• Obtain laboratory tests where appropriate and consult with specialty providers if necessary.
• Be aware that other practitioners may also have minimal historical information that can result in misdiagnosis.
• There are common psychotropic side effects that can often be missed. People with IDD have atypical nervous system functions, responses, and reactions, as well as other organic system anomalies and are at an elevated risk for a variety of health problems, but also for adverse drug events.

References

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8. National Institutes of Health. Cerebral palsy. https://www.ninds.nih.gov/health-information/disorders/cerebral-palsy. Accessed October 10, 2025.
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10. National Institutes of Health. What conditions or disorders are commonly associated with Down syndrome? https://www.nichd.nih.gov/health/topics/down/conditioninfo/associated. Accessed October 10, 2025.
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