Autism Spectrum Disorder Is Underdiagnosed in Older Adults

A lack of appropriate diagnosis of ASD in the elderly can lead to health care related issues and costs that could have been avoided if the condition had been treated earlier.

Autism is a heterogeneous psychiatric disorder that encompasses communicative and social impairments, with patients exhibiting restricted, stereotypical patterns of behavior and interests.1

The diagnostic criteria for autism were updated in the Diagnostic and Statistical Manual of Mental Disorders5thedition in 2013 from the previous 4th edition.1 Historically, they were largely associated largely with a younger population, and the research in this area has not focused extensively on life outcomes for older adults diagnosed with this condition.2 However, over time there have been greater attempts to examine the connection between aging and autism spectrum disorder (ASD), which is a neurodevelopmental disorder that can cause impairments in social communication and repetitive and restrictive behaviors. ASD is placed under this category, along with 4 others.

Autism it is not a single disorder but rather multi-factorial, and it can develop from a number of risk factors and interactions.3,4 Diagnosis is generally made based on the key feature of an early onset of difficulty engaging in communications and social interactions, along with repetitive behaviors, activities, or interests.5 ASD can be missed in older adults, so it is important for health care professionals who work with geriatric populations to be aware of the potential for ASD in older adults.

Epidemiology of ASD

Behind intellectual disability, ASD is the second-most-common developmental disorder.6 In 2010, it was reported that about 52 million people diagnosed with autism account for more than 111 disability-adjusted life years per 100,000 population.7 Several factors can lead to autism, including environment and genetics.8 It has been suggested that more than half of all adults diagnosed with autism have some degree of intellectual disability.8

The worldwide prevalence of ASD is reported at 0.76%, according to the World Health Organization.9

Between 2000 and 2002 and 2010 and 2012, it was reported that the prevalence of ASD more than doubled.9 However, the prevalence of ASD remained stable in the United States, with no statically significant increase, but this might have been related to the change in diagnostic criteria with the release of the Diagnostic and Statistical Manual of Mental Illness, 5th edition.10

ASD is thought to be more prevalent in males than females, but study findings vary, with some noting a 3:1 or 4:1 ratio.9,10 There are several genetic diagnoses that have the potential to increase the diagnosis of ASD in comparison with the average population. These include fragile X, Rett syndrome, or tuberous sclerosis.11 Other potential risk factors that can lead to the increased risk of autism include older age of the mother and prematurity at birth. When treating older adults, it is important to evaluate their medical background and pre-existing conditions to determine potential causative factors, such as comorbid psychiatric conditions, if possible. However, there are instances in which the origin of an autism diagnosis may never be realized. It typically takes a thorough assessment to fully determine the contributing factors. It can prove to be challenging for some individuals as they transition through the phases of life, learning how to adapt with the potential associated burden and costs of ASD management.12

Possible Causes

The presence of ASD can be complex, given the regions of the brains that can be affected by the condition. There are a number of interrelated biomedical factors that can play a role in ASD development.13 Examples of these biomedical factors include food insensitivity or intolerance, nutritional deficiencies (eg, magnesium; vitamins A, B, and D; and zinc), oxidative stress, or poor detoxification.13 The impact of each of these factors varies depending on the individual, so this must be taken into consideration when it comes to the management approach.13 ASD is regarded as a neurodevelopment abnormality that presents during early childhood. There are many genes that have been proposed as involved in the pathogenesis of ASK, and the majority are involved in neuronal synaptogenesis.14 Although it is theorized that there is a strong genetic basis for the development of ASD, there are several associated factors that can be tied to the pathogenesis and bring about the initial presentation. In both children and older adults who suffer from ASD gastrointestinal issues may be present, such as abdominal pain, constipation, nausea, and vomiting.14

The areas of the brain that are involved through neuroanatomic and neuroimaging studies include the cerebellum and frontal and temporal lobes.15 There is an observed growth of the amygdala and the hippocampus, which can be observed during childhood. In addition, the analysis of magnetic resonance imaging has shown evidence of variations in the connectivity and neuroanatomy among those who are diagnosed with ASD compared with those who are not.15 These particular studies have been able to identify abnormal or lower connectivity in the frontal regions of the brain, along with thinning of the corpus callosum in adults and children with ASD.15 Depending on the region of the brain that is affected, this can influence the severity of autism symptom presentation.16 For instance, if there is impairment associated with language in a person diagnosed with ASD, this can be related to a dysfunction of the frontal and temporal lobes.17 The nuances of ASD can include quantitative impairments in communicative and social behavior, so an evaluation of various brain regions that may be associated with development is important when making a firm diagnosis.18

Screening and Diagnosis in Older Adults

ASD can be underdiagnosed in older adults, which is why the screening progress is very important in making a diagnosis if not made in early life.18,19 There is a lack of substantive awareness of ASD among mental health professionals who work with older adults. The lack of appropriate diagnosis of ASD in older adults can lead to the introduction of health care problems and associated costs that could have been avoided.20 Given the recent establishment of ASD, it is thought that many older adults might not have received a diagnosis, because the condition was not understood when they were younger. It is only through revisions of the Diagnostic and Statistical Manual of Mental Illness that ASD has been recognized.21 With increased recognition comes the ability of many older adults who were once misdiagnosed to receive the appropriate diagnosis. To do this, a thorough screening must be performed. In some cases, older adults can go through their whole lives without knowing that they have ASD, and it is only after much analysis that it is identified. The inability to identify the presence of ASD early on has the potential to lead to significant complications in later life.19-21 To sufficiently make a diagnosis of ASD, a clinician must be aware of possible differential diagnoses that can have similar presentation. These can be complicated, particularly in older adults, because of the potential for overlap with other conditions.22 For example, there can be an overlap between ASD and personality disorders because both can be influenced by age-specific factors and present with similar behavioral symptoms.22 To fully understand the specific elements of ASD and personality disorders, more research is needed, along with assessment instruments for older adults with comorbid mental disorders and personality disorders.22

To successfully diagnosis ASD, a thorough background and history must be taken of any older adult. Additional information can also be obtained from caregivers and loved ones.22,23 In addition, there are a variety of screening tools that can be employed to assess behaviors that can align with an ASD diagnosis, such as the Adult Repetitive Behavior Questionnaire, with the goal of determining if behaviors are frequent or severe. This screening tool is only for the behavioral elements of ASD, so the social aspects would need to be assessed with a supplemental tool.24

Co-Occurring Psychiatric Conditions

Given the complex nature of ASD it is understandable that other conditions can occur alongside the condition, which can also make diagnoses challenging. Older adults with ASD can be at increased risk of having 1 or more psychiatric conditions.25 The presence of these psychiatric conditions along with ASD can contribute to more distress and impairment in older adults and potentially to caregivers and family members. The degree of burden from ASD is thought to be comparable to that experienced with acquired brain injury.26 The most common comorbidities among those with ASD include anxiety disorders, attention-deficit hyperactivity disorder, and mood disorders, which can lead to increased contact with health care services.27 At times, these co-occurring conditions can go unnoticed, but once they are identified, there are available treatment options.27 To effectively manage the co-occurring conditions, it is important for clinicians to understand the overlap that can occur and other potential challenges. Although there are no screening tools for psychiatric comorbidity with ASD, there is a growing movement toward its development. The use of reliable and valid screening tools is an important step toward early identification of ASD and potential co-occurring conditions.

Impact on Caregivers and Families

The experience of caring for an older adult with ASD can be a challenge for any caregiver or family member. The pervasive and significant deficits that can present in older adults with ASD can be associated with myriad difficulties with providing optimal care. Some of these issues can include financial strain or increased mental and physical problems, such as stress.28 Given that caregivers and family members may provide most long-term care to older adults with chronic disabilities and illnesses, including ASD.29 Caring for an older adult can be particularly stressful and have a negative impact on mental health and well-being. Along with providing adequate care to older adults, it is equally important for caregiver and family members to be aware of the impact on them and take measures to implement self-care interventions into their daily routines. They should also seek assistance if the burden becomes too great.

ASD Prognosis

It can be difficult to determine the progress of ASD in children over their lifespans, but about 9% of children who are diagnosed with ASD in early childhood do not necessarily meet the criteria for ASD when they become adults.10 The direction that the diagnosis of ASD takes can be dependent on certain factors, such as early childhood intervention or a reduction in repetitive behaviors over time. There are instances in which older adults with ASD experience high levels of functionality and quality of life, which can be tied to the presence of a support system.10 It is possible for older adults with ASD to live a normal life either by themselves or with the aid of caregivers or family members.


There is still much to learn about older adults with ASD, and research continues to advance in this area. As life expectancy rates in the United States continue to increase, so do the lifespans of those with ASD. There is greater emphasis being placed on ASD in relation to aging and ensuring that individuals with ASD are screened and diagnosed in a timely manner and have appropriate long-term management of their condition when applicable.30 Older adults with ASD can face many difficulties, such as communication problems, lack of advocacy or support, and social isolation.30


Abimbola Farinde, PhD, PharmD, is a professor of health care administration at Columbia Southern University College of Business in Orange Beach, Alabama.



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