Five Essential Concepts of Developmental Medicine
A Medical Paradigm for People with Developmental Disabilities
By Ryan Daniel, MD, Bronwyn Bennett, MS, Linda Edwards, MD, Philip May, MD, and Rafik Jacob, MD
Summary: Adults with developmental disabilities and neurodevelopmental disorders often face complex health needs as they transition from pediatric to adult care. This article introduces the “Five Essential Concepts of Developmental Medicine,” a clinical framework designed to support individualized assessment, prevent diagnostic overshadowing, and guide proactive, multidisciplinary care across the lifespan.
The major functions of the brain include memory and learning, control of motor function, routing of sensory input, and emotional regulation. These functions depend on the coordinated activity of specific, interrelated brain structures. When these relationships are improperly developed or disrupted, brain dysfunction occurs. Regardless of the cause or age of onset, the primary symptoms of brain dysfunction in both children and adults include cognitive impairment, neuromotor dysfunction, seizures, and or impulsive destructive behaviors.
These symptoms may appear independently or in combination and can range from mild to severe. For example, cognitive dysfunction may manifest as mild dyslexia or as profound intellectual disability. Neuromotor dysfunction may range from mild spastic hemiplegia to severe choreoathetosis. Seizures vary in severity, from brief absence episodes to generalized tonic-clonic convulsions. Behavioral dysregulation spans from mild impulsivity to severe self-injurious episodes. By convention, these four symptom domains are considered the primary complications of neurodevelopmental disorders (NDDs).
NDDs arise from genetic or acquired factors that interfere with brain development during a critical window extending from embryological formation to approximately 22 years of age. These disorders result in chemical or structural abnormalities in the brain, which manifest as one or more of the four primary complications: cognitive impairment, motor dysfunction, seizures, and behavioral challenges. Although these complications often cause substantial functional limitations in daily living, the degree of impairment can vary widely.
Both inherited and spontaneous genetic mutations can disrupt normal brain development. Environmental insults, including prenatal infections, exposure to toxins, perinatal injuries, or postnatal trauma, also can contribute. When no cause is identified, continued investigation remains essential to guide clinical care and prognosis across the lifespan.
As children with NDDs transition into adulthood, many continue to live with persistent and evolving medical needs. Despite this, adult healthcare systems are not consistently structured to meet their complex needs. Many providers are less comfortable managing the health care of patients with NDDs compared with the general patient population. The transition from pediatric care to adult care can be made difficult by insufficient handover and a lack of continuity. Pediatric care is more integrated, with various specialists working together and studying the child for the first 2 decades of life, whereas adult care tends to be more fragmented and uncoordinated. There are fewer community, financial, and social support resources for adults with NDDs compared with their pediatric counterparts. Lastly, adult healthcare systems frequently lack accommodations for sensory sensitivities, behavioral needs, communication barriers, and procedure adaptations. People with NDDs are at risk of experiencing a harsh transition from accommodating, familiar pediatric healthcare centers to inadequate adult healthcare centers.
Many individuals with severe NDDs now survive into adulthood and are increasingly expected to reach a normal lifespan. For example, the mean lifespan of people with Down syndrome increased from 10 years in 1960 to 47 years in 2010.1 These individuals, however, frequently continue to experience complications that, in turn, contribute to secondary health conditions. For instance, immobility related to motor dysfunction may increase the risk of osteoporosis, chronic lung disease, or esophageal cancer conditions typically encountered in geriatric populations, now manifesting earlier in medically fragile adults with DDs.
In addition to complications and consequences of brain dysfunction, syndrome-specific conditions often emerge based on the underlying diagnosis. For example, individuals with Down syndrome may develop congenital heart disease, thyroid dysfunction, or early-onset Alzheimer disease. It is critical for clinicians caring for adults with DDs to differentiate between complications arising from brain dysfunction and additional syndrome-specific risks requiring targeted surveillance and intervention.2 Many secondary medical conditions can arise from these neurodevelopmental dysfunctions, including sleep disorders such as obstructive sleep apnea, which can further impair cognition and behavioral function. Hearing and vision impairment may go unnoticed for extended periods of time and worsen communication and social deficits.3
The term “developmental disability” often is misunderstood. It carries medical, legal, and social implications. Legally, individuals who meet eligibility criteria onset before age 18 years and have a chronic condition that entails significant limitations in daily living qualify for Medicaid services. Psychologists typically use two standardized assessments: a cognitive ability test (eg, Stanford-Binet IQ test) and an adaptive functioning measure (eg, Vineland scale). Eligibility does not require a specific diagnosis, and many adults are left with vague labels that obscure the underlying medical complexity.
Although NDDs cause DDs, the eligibility process does not mandate identification of the precise disorder. Labels such as intellectual disability, cerebral palsy, epilepsy, and autism, although used commonly, may lead to diagnostic overshadowing, and all medical symptoms are mistakenly attributed to the disability.4 This phenomenon is especially problematic in adults, who may present with evolving or atypical manifestations that deserve thorough medical reevaluation.
A more effective clinical model views patients as individuals with chronic brain dysfunction resulting from a specific NDD, each with distinct complications, consequences, and syndrome-specific risks. Adopting this framework allows for more comprehensive and individualized care throughout adulthood.
To support this approach, the American Academy of Developmental Medicine & Dentistry introduced the Five Essential Concepts of Developmental Medicine, each corresponding to a key clinical question:
Childhood-onset brain dysfunction: Are there signs or symptoms of brain dysfunction?
NDD: What is the specific diagnosis (eg, Down syndrome, Angelman syndrome, fragile X)?
Complications: Which of the four primary dysfunctions are present?
Consequences: What secondary medical conditions arise from these complications?
Syndrome-specific conditions: Are there risks unique to the specific diagnosis?
This conceptual framework provides a structured, equitable approach to primary care, especially for adults with intellectual and DDs, a population that historically has been marginalized within the healthcare system despite increasing longevity and complexity of care needs.5
Consider the following example of this framework for Down syndrome. Signs or symptoms of brain dysfunction may include intellectual disability, deficits in adaptive functioning, impaired verbal communication, and decreased executive functioning. The specific diagnosis is Down syndrome or trisomy 21. All four domains may be implicated: cognitive impairment, motor dysfunction, seizures, and behavioral challenges. Cognitive impairment may include learning disabilities, executive function deficits, expressive communication difficulties, shorter attention span, and impaired short-term and working memory.3 Motor dysfunction can include hypotonia and coordination deficits. Individuals with Down syndrome have a higher rate of seizures than does the general population.6 Behavioral problems associated with Down syndrome entail inattention, impulsivity, noncompliance, anxiety, social withdrawal, autism spectrum disorder, repetitive behaviors, and, less often, aggressive and self-injurious behaviors.7 These complications increase the risk of secondary medical conditions. Depression and anxiety are more common in individuals with cognitive impairment. Hypotonia and intellectual disability contribute to more sedentary lifestyles, which may be further exacerbated by selective food choices, greatly increasing the risk of obesity and cardiometabolic disease.8 Those with severe motor impairment have a higher risk of developing secondary complications such as pressure ulcers and pneumonia. Seizures and motor impairment predispose individuals to injury, falls, and fractures. Syndrome-specific conditions include early Alzheimer disease, obstructive sleep apnea, hearing and visual impairments, hypothyroidism, autoimmune disorders (eg, type 1 diabetes mellitus, alopecia), celiac disease, leukemia, atlantoaxial instability, and congenital heart disease.7
Although the US Preventive Services Task Force does not release screening guidelines specifically for adults with DDs, independent organizations create screening guidelines tailored to the specific conditions and comorbidities of adults with various NDDs. The American Academy of Family Physicians and the Global Down Syndrome Foundation jointly recommend annual dementia screening starting at age 40 years for adults with Down syndrome; hemoglobin A1c and obesity screening every 2 to 3 years beginning at age 21 (earlier if other diabetes mellitus risk factors are present); and screening for hypothyroidism, with a thyroid-stimulating hormone level every 2 to 3 years beginning at age 21.9 The International Rett Syndrome Foundation recommends annual electrocardiogram screening to check the QTc interval, annual vitamin D level, and biennial urinalysis.10
When specific screening guidelines do not exist, preventive and routine health maintenance should follow age-appropriate guidelines for the general population, with individualized considerations for comorbidities associated with the patient’s NDD.
Adults with NDDs may require sedation or anesthesia for dental procedures, Pap tests, endoscopies, and other minor procedures; careful risk–benefit analysis and assessment of individual risk factors are required in these situations.11 Individuals with NDDs tend to live more sedentary lives and have significantly greater rates of obesity than the general population, predisposing these individuals to cardiometabolic disease.9 Adults with intellectual disability are at a markedly higher risk for developing type 2 diabetes mellitus, hypertension, hyperlipidemia, osteoporosis, atherosclerotic cardiovascular disease, and early mortality. Accordingly, height, weight, body mass index, nutrition, and exercise should be monitored routinely at primary care visits, with risk assessment for cardiometabolic disease.12 Regular surveillance is warranted for conditions that may present atypically in this population, such as vision and hearing deficits, endocrine or metabolic disorders, pain, dysphagia, dental caries, sleep apnea, urinary retention, kidney stones or gallstones, urinary tract infections, deconditioning, nutritional deficiency, abuse or neglect, and polypharmacy.13 A multidisciplinary approach is recommended, involving primary care and specialists as well as community, social, and legal support.
A DD is defined as a childhood-onset condition that leads to significant functional limitations in activities of daily living. Although this status may qualify individuals for supportive services, including vocational programs, housing, and recreation, medical care has not been integrated into these systems consistently. This is particularly problematic in adulthood, when the education-based supports of childhood fall away, but medical complexity persists or increases. Most healthcare professionals lack training in the needs of medically complex adults with DDs. Historically, care systems have focused on education and residential support, domains in which physicians have limited involvement. Although this model may suffice for healthier individuals with mild disabilities, it is inadequate for those with complex, lifelong medical needs.
Legislative efforts such as the Healthcare Extension and Accessibility for Developmentally Disabled and Underserved Population Act of 2025 (H.R. 3409) aim to bridge this longstanding gap. By designating individuals with intellectual and DDs as part of a medically underserved population, the act promotes workforce development through tuition assistance and J-1 visa waivers for physicians. It also supports grants for continuing education. The act, if passed, would fund medical and dental schools to establish training and fellowship programs focused on adults with NDDs, mirroring existing developmental and behavioral pediatrics programs for children.
This legislation presents a timely opportunity to establish formal academic collaborations, enhance clinical research, and develop interdisciplinary training programs specifically targeting adult care.
It is important to distinguish a NDD (a medical diagnosis such as phenylketonuria, fragile X, or cerebral palsy) from a DD (a functional status based on limitations). Identifying the specific disorder is critical because it helps predict complications and anticipate syndrome-specific risks. Consider the following case.
Robert, a 54-year-old man with severe intellectual disability, was institutionalized for self-injurious behavior. At age 42, an amino acid panel revealed elevated phenylalanine, leading to a diagnosis of previously unrecognized phenylketonuria. Dietary intervention corrected his biochemical profile, improved his behavior, resolved a persistent skin rash, and eliminated the need for antipsychotics. Although his cognitive impairment remained, his overall health and quality of life significantly improved.
This case illustrates the critical importance of reevaluation and diagnostic precision in adults, even decades after the onset of the DD. Regardless of the underlying disorder, most adults with neurodevelopmental conditions experience at least one of four complications: cognitive dysfunction, motor impairment, seizures, or behavioral dysregulation. These complications frequently contribute to further consequences—for example, motor impairment leading to poor oral hygiene and periodontal disease or immobility resulting in osteoporosis.
In conclusion, delivering high-quality care for adults with DDs requires clinicians to identify the specific neurodevelopmental diagnosis, assess associated complications, monitor for secondary consequences, and screen for syndrome-specific conditions. This comprehensive approach supports proactive, adult-centered management, improves quality of life, and fosters greater independence, ultimately reducing reliance on public support systems and ensuring that adults with NDDs receive the equitable care they deserve.
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