Motor problems in autism: Co-occurrence or feature?

Abstract

Motor features of autism have long been acknowledged by clinicians, researchers, and community stakeholders. Current DSM-5 and ICD-11 guidelines allow clinicians to assign a co-occurring diagnosis of developmental [motor] coordination disorder (DCD) for autistic individuals with significant motor problems. DCD is characterized by poor motor proficiency with an onset of symptoms in early development. Studies have shown considerable overlap in the behavioral motor features observed in autism and DCD. However, others indicate that motor problems in autism and DCD may stem from different underlying sensorimotor mechanisms. Regardless of whether autism has a unique motor phenotype or an overlap with DCD, changes need to be made in the clinical pipeline to address motor problems in autism at the stages of recognition, assessment, diagnosis, and intervention. Consensus is needed to address unmet needs in research on the etiology of motor problems in autism and their overlap with DCD, to optimize clinical practice guidelines. The development of screening and assessment tools for motor problems that are valid and reliable for use with autistic individuals is essential, and an evidence-based clinical pipeline for motor problems in autism is urgently needed.

Many neurodevelopmental conditions are accompanied by motor problems that are functionally relevant, but may not be assessed or prioritized in intervention planning. Several recent studies have documented a high prevalence of clinically significant motor problems in those with an autism spectrum disorder (ASD) diagnosis, ranging from 50% to 95%.^1–4 These are present across many domains, including functional mobility, physical activity, participation and competence in activities of daily living, and fall risk. Motor problems present a significant barrier to the performance of daily living activities, as well as for social and cognitive development.

The purpose of this review is to provide an overview of common motor features in autism and discuss opportunities to improve identification and intervention for motor problems in this population. At present, Internationa Classification of Diseases, 11th Edition (ICD-11)⁵ and DSM-5⁶ guidelines permit clinicians to diagnose autistic individuals with co-occurring developmental [motor] coordination disorder (DCD), a neurodevelopmental condition of poor motor proficiency that affects activities of daily living. However, while it seems that a high percentage of autistic individuals meet the clinical criteria for DCD,³ very few actually receive a DCD diagnosis. Given that motor problems are a common and overlooked feature of autism, they may be better recognized and addressed by adding a domain-specific ‘specifier’ to the ASD diagnostic criteria.¹ Here, we provide an overview of the recent literature and present a case for a more uniform structure to the assessment and treatment of motor problems in autism.

MOTOR PROBLEMS IN AUTISM

There is strong empirical evidence that autistic individuals have differences in motor behavior compared to neurotypical individuals. These can be separated into two categories: motor stereotypies (e.g. hand flapping) and differences in motor control and motor coordination (e.g. postural instability, hand–eye coordination). The scope of this discussion is focused on motor control and motor coordination differences, not motor stereotypies, as these are captured under DSM-5 diagnostic criteria and defined separately in the ICD-11 under 6A06. These motor differences persist in a variety of domains across the lifespan. A recent systematic review demonstrated that infants later diagnosed with autism exhibit significant motor differences,⁷ including delays in achieving motor milestones,⁸ and fine and gross motor problems in infants at an elevated likelihood of being autistic between 6 months and 36 months.^1,9 Studies have demonstrated the persistence of these differences beyond childhood into adulthood, for example, in the domains of static and dynamic balance^10,11 and locomotion.¹² Motor problems have also been highlighted when using screening measures used to identify those at risk of coordination difficulties,² broader measures of adaptive functioning,¹ and criterion-standard observational measures of motor proficiency.³

Importantly, motor problems are as prevalent and functionally impactful as other domains recognized as specifiers to an ASD diagnosis (e.g. intellectual and language impairment).¹ For example, intellectual disability is a common specifier for ASD, and prevalence estimates indicate approximately 30% to 50% of autistic individuals have an intellectual disability. This rate is substantially lower than current prevalence estimates of motor problems in autistic individuals on both parent-reported measures (87%)² and observational measures (97%; 85%).^3,13 However, clinicians currently document motor problems in only around 1% of autistic individuals,^1,3 highlighting a serious need for improved recognition and documentation of motor problems in autism.

LIFESPAN FUNCTIONAL AND HEALTH CONSEQUENCES OF MOTOR PROBLEMS IN AUTISM

Autistic individuals’ persistent motor problems have a lifelong impact on developmental opportunities, and a downstream effect on daily living.^1,14,15 Childhood consequences of motor problems include limited access to object and environment exploration, difficulty engaging with peers during play, and difficulty building non-verbal communication skills. Motor delays in sitting and crawling¹⁶ and limited use of motor skills during social interactions¹⁷ are among the earliest markers in children later diagnosed with ASD. Further, a recent systematic review of 114 motor studies (total n > 6000) found that gross motor performance in autistic children was strongly associated with social communication performance, noting large effects for gross motor problems in autistic compared to neurotypical children.¹⁸ Problems with locomotion, postural control, and manual dexterity limit autistic children’s ability to comfortably engage in self-care behaviors including eating, bathing, toileting, and dressing.¹⁹ Autistic adolescents’ and adults’ manual motor skills correlate not only with concurrent daily living skills but also predict subsequent daily living skills up to 8 years later.²⁰ Autistic children and adults also experience barriers to physical activity including perceived difficulty and motor challenges.^21,22 However, little is known about the long-term impact of decreased physical activity frequency and intensity across the lifespan of autistic individuals, or the specific physical, environmental, and social barriers they may encounter.²³ There is an approximately 33% greater prevalence of overweight and obese autistic adolescents compared to neurotypical adolescents,²⁴ placing them at risk for long-term health consequences. A recent longitudinal study tracking physical activity of autistic individuals from age 9 to 18 years found that autistic children became more physically inactive with age compared to neurotypical children.²⁵ Given these findings, it is clear that there is a critical need to identify and address motor problems in autism early, and improve access to intervention and accommodation across the lifespan.

ASSESSMENT OF MOTOR PROBLEMS

Early recognition of motor problems is a prerequisite for early intervention and is vital in the prevention of secondary adverse outcomes, such as physical inactivity and academic difficulties. However, given the heterogeneous nature of motor problems in autistic children and adolescents, a comprehensive assessment battery is necessary to capture potential problems across different motor domains. Especially for autistic children, the administration of such a comprehensive motor assessment can be challenging. Conversely, screening for motor problems by means of a caregiver-reported questionnaire can optimize the cost–benefit ratio and reduce the time and effort burden on all parties. Previous research indicates that the Developmental Coordination Disorder Questionnaire, a 15-item caregiver-reported questionnaire, can be used to detect motor problems in autistic children.²⁶ Adding a brief screening tool like the Developmental Coordination Disorder Questionnaire to standard clinical procedures would provide clinicians with information about a child’s motor skills that may not be observable during routine visits. This information can help guide decision-making with regard to whether a full motor assessment is necessary.

For children with motor problems, comprehensive assessment may be needed to determine the specific domains in which they require support or intervention. Several standardized observational measures are available for this type of assessment, and may be appropriate for use in autism. For example, the Movement Assessment Battery for Children (currently in its second edition) has been used successfully to detect motor problems in autism.^2,4,14,26 The use of observational measures such as the Movement Assessment Battery for Children as part of standard clinical practice of assessing autistic individuals’ motor skills can provide clinically relevant information about their manual dexterity, eye–hand coordination, bilateral coordination, and balance. Other movement assessments that have successfully been used to characterize motor profiles in autism include the Bruininks-Oseretsky Test of Motor Proficiency, Second Edition, Test of Gross Motor Development, Third Edition, and the Beery-Buktenica Developmental Test of Visual-Motor Integration, Sixth Edition. However, there is a lack of assessments that last through adulthood, with the Bruininks-Oseretsky Test of Motor Proficiency being the only one that can be used up to 21 years of age. It is important to consider that some assessments are especially useful with a visual support protocol, for example, the Test of Gross Motor Development.²⁷ Depending on the specific areas of motor problems an individual appears to experience, a combination of these measures may be needed to sufficiently inform intervention and support planning. Further research is needed to assess the validity and reliability of observational motor assessments in autism across the lifespan.

Despite evidence for screening and assessment of motor problems in autistic individuals, it has been suggested that motor delays and impairments are potentially explained by lack of interest or motivation, difficulty managing social demands, or differences in intellectual ability, among other factors. Discounting the fundamental nature of motor differences in autism—independent of cognitive or social factors that may exacerbate their manifestation in assessment contexts—does a disservice to the autistic community. It does not presume intellectual and communicative competence and perpetuates ableist stereotypes that autistic individuals only experience motor problems because they cannot understand instructions or lack motivation to perform.²⁸ Certainly, communication differences can present challenges in any assessment setting. For that reason it is important for assessments to be done by professionals who are experienced in working with autistic individuals, to ensure that the observed motor behaviors are not better explained by other factors. But there is a large body of evidence that autistic adolescents and adults have problems in motor domains that do not involve instruction in daily living, such as standing balance and walking as described previously. Further, many studies of autistic movement use assessment paradigms that have been shown to be engaging and accessible for autistic individuals. Continued research on the validity of standardized motor assessments in autism and clinical application of these assessments is needed to raise awareness of the fundamental nature of motor problems in autism, independent of cognitive and social skills.

IS IT CO-OCCURRING DCD?

Once motor problems are identified via appropriate assessments, clinicians are faced with the challenge of assigning diagnostic codes or labels and making recommendations for accommodations or interventions. Although a co-occurring diagnosis of DCD is permitted by ICD-11⁵ and DSM-5,⁶ questions remain about whether this is the best approach. Unquestionably, there remains a need for further research to determine whether motor problems in autism are distinct from those observed in other neurodevelopmental conditions like DCD in their etiology, manifestation, and functional impact.^29,30 In the meantime, however, there is a human cost to taking a ‘wait and see’ approach before addressing this issue in clinical practice. Autistic children, adolescents, and adults experiencing motor problems may not have the information or documentation necessary to access accommodative supports or intervention services. Since motor problems are not a recognized feature of autism under the current guidelines, insurers and education systems are often reluctant to provide coverage or resources unless a clinician also assigns a co-occurring motor diagnosis (i.e. DCD).

Even though it can be helpful in circumstances where autistic people would otherwise not have access to care for motor problems, assigning a DCD diagnosis is not a panacea in all cases. There are three issues with a co-occurring diagnosis that may present barriers to care for some autistic individuals. First, a diagnosis of DCD is not currently recommended until at least 5 years of age,³¹ to account for natural variability that exists in the attainment of motor skills. The problem with this age-related barrier is that a critical therapeutic window to support the development of motor skills is likely to be missed. Second, if a diagnosis of ASD is assigned before 5 years of age (as currently recommended), a later, secondary diagnostic evaluation for DCD may place additional financial and time burden on families and clinicians. Evaluation for DCD may be particularly difficult for families to access, or not presented to them as an option, since DCD is under-recognized and underdiagnosed in the general population³² and in autism.^1,2 Third, some motor problems seen in autism are distinct from features seen in individuals diagnosed with DCD, and so clinicians may be hesitant to assign co-occurring DCD as a co-occurring diagnosis. This is perhaps the most challenging issue, as there is limited research in this area on which to base a clinical practice guideline or consensus.

An overview of the few studies that have compared autism to DCD have found that problems with general motor ability as measured by the Movement Assessment Battery for Children assessment are comparable between the two groups.^3,13 However, for certain praxis skills, such as imitation of meaningful actions and gesture to command, autistic children perform significantly worse than children with DCD, and in the autism group only, imitation errors correlate with emotion recognition ability.¹³ Thus, while general motor ability (i.e. balance, manual dexterity, and aiming/catching) may be comparable between autism and DCD, autism may be distinguished by poorer performance on imitation of meaningful gestures and other praxis skills.

MOTOR IMPAIRMENT AS AN ASD SPECIFIER

Currently, there is a clear research-to-practice gap in the recognition and management of motor problems in autism. Given that motor problems in autism are similar but not always identical to those observed in DCD, resolving this gap is challenging. One possible solution is to add ‘with or without accompanying motor impairment not otherwise explained by motor stereotypies’ as a domain-specific specifier to the ASD diagnostic criteria. The addition of a motor specifier would increase the likelihood that motor problems are assessed, documented, and managed in concert with other autistic traits, similar to the current practice for other domain-specific specifiers (i.e. language and intellectual impairments). Although motor stereotypies are already captured under the restricted, repetitive behaviors domain of the ASD diagnostic criteria, the full breadth of motor differences (e.g. motor control, motor coordination) observed in autism are not well represented by the current taxonomy. Affirming a motor specifier could serve as a triggering event for referral to comprehensive motor assessment (e.g. by neurologists or physical/occupational therapists). It would also enable autistic individuals to access motor-related services or accommodations, including before the age of 5 years, before a co-occurring diagnosis of DCD could be considered.

Adding motor problems as an ASD specifier may, therefore, be an effective stop-gap approach while research studies continue probing underlying etiology and diagnostic overlap with DCD. If future studies determine that the etiology of motor problems in autism are distinct from those observed in DCD, then a co-occurring diagnosis of DCD may not be needed or appropriate in some cases. If future studies determine that the etiology of motor problems in autism overlaps substantially with those observed in DCD, then the specifier would still serve as a triggering event for assessment and a means of accessing early motor intervention with less difficulty. It would, in essence, help to establish a clinical pipeline for screening, evaluation, and management of motor problems and DCD in autism. Finally, but certainly not of least importance, adding motor problems as a specifier would bring needed attention to this issue in the clinical and caregiver community. Given that motor problems are present in most autistic children in observational research studies but only diagnosed in approximately 1% of autistic children in clinical practice, increased awareness is the first step toward bridging the research-to-practice gap.

COMPLEX INTERRELATEDNESS BETWEEN MOTOR SKILLS AND OTHER DOMAINS

Current evidence from large sample studies indicate that motor difficulties are present in children with ASD with and without intellectual disability and they continue to predict autistic traits and language and functional delays even after controlling for cognitive delays. Therefore, while it is true that motor difficulties are greater in individuals with ASD and intellectual disability, they continue to negatively impact communication and functioning in the majority of autistic individuals, including autistic children without intellectual disability.³³

The complex interrelationships between IQ, language, sensory, and motor differences in autism are evident in the dual task literature where the level of performance difference is affected by task complexity.^8,34,35 It is also evident in some studies relating motor skills with IQ, language, and sensory skills. In preschool autistic children, IQ scores are positively related with fine motor skills.³⁶ Furthermore, social and communication functioning has been found to be positively related to manual dexterity and fine motor skills in autistic children and adolescents.^37,38 While some studies have found that the relationship between motor skills and daily living skills is mediated by IQ in adolescence,³⁹ others have found that sensory reactivity and motor skills uniquely contribute to daily living skills independent of IQ in early childhood.¹⁴ Despite this literature, it remains unknown if the presence of a greater number and magnitude of autistic traits exacerbates motor difficulties, or if early motor difficulties negatively impact the developmental affordances required for acquisition of cognitive, social communication, and other skills.⁴⁰

Regardless of the outcome of this debate, motor differences have a clear and persistent impact in autism. Motor differences are still evident even when there are not competing cognitive, sensory, or language demands (e.g. quiet standing under normal visual and proprioceptive conditions).⁴¹ Additionally, motor differences predict later development even when controlling for IQ, language, and sensory domains. In a longitudinal study of 209 autistic children, autistic children’s gross motor skills at 2 years of age predicted subsequent expressive and receptive language up to 9 years of age even when controlling for IQ and autism symptoms.⁴² These findings indicate that there is likely variability in the effects individual domains have on autistic individuals’ functional abilities. The challenge of teasing out the relationships between these domains and their impact on functional abilities makes it difficult to identify the mechanisms underlying motor problems in autistic individuals. However, consideration needs to be given to understand these complex interactions to enable more targeted interventions and accommodations for the specific needs of autistic individuals.

AWARENESS AND ACCESS TO CARE

For decades, stakeholders in the autistic community have been calling for researchers and clinicians to direct more attention toward issues that affect their physical health, mental health, and well-being.⁴³ Motor skills have known effects on each of these areas, and motor skills interventions could provide significant improvements for autistic individuals’ quality of life. The addition of motor impairment as a diagnostic specifier would not only elevate community awareness of the presence and impact of motor problems in autism, but also open new doors to physical therapy, occupational therapy, and other motor skill interventions and accommodations.

Further, access to motor interventions and accommodations could provide autistic individuals with opportunities to improve their physical and mental health. Physical health improvements may be achieved through increased access to or comfort with physical activity, decreased likelihood of falls or other injuries, and decreased risk of chronic health conditions such as obesity. Mental health improvements may be achieved through affirmation of lived experiences with motor problems and amelioration of frustration due to lack of explanation for these problems, improved self-esteem, access to information about accommodations and tools for self-advocacy in school or the workplace, and reduction of the social isolation and limited participation commonly observed among individuals with untreated motor problems.

There is precedent for modification to the ASD diagnostic criteria based on emerging scientific evidence. In addition to the aforementioned specifiers for intellectual disability and language skills, sensory difficulties were added to the diagnostic category of restricted and repetitive behaviors. Yet, despite overwhelming evidence of its clinical relevance, motor problems are still absent from the criteria. Gaps in motor development increase over time, such that by 5 years of age, the motor skills of an autistic child are at the level of a child half their age.⁴⁴ Yet, access to motor-related services (e.g. occupational therapy/physical therapy) decreases dramatically with age.⁴⁵ This creates a clear unmet need that is not currently addressed in clinical practice.

It is critical to increase awareness of motor problems in autism and establish a clear pipeline for screening, assessment, and management. This pipeline should include a variety of clinic- , school- , and community-based services, including both motor skills interventions (e.g. occupational therapy/physical therapy) and adaptive recreation and fitness activities. This pipeline must be accessible to individuals across the lifespan, so that those diagnosed later in life do not fall through the cracks.

CONCLUSION

Regardless of whether autism has a unique motor phenotype or an overlap with DCD, changes must be made in the clinical pipeline to address motor problems in autism at the stages of recognition, assessment, diagnosis, and intervention/accommodation. Collaboration between community stakeholders, researchers, and clinicians is urgently needed to address this unmet need. We must continue research on the etiology of motor problems in autism and their overlap with other clinical conditions like DCD, in order to develop optimal clinical practice guidelines. What additional literature is needed to build consensus on the significant and ubiquitous presentation of motor problems in autism, and to prompt a change in current practices?

Autistic individuals deserve comprehensive care, including support for motor problems. This will ensure that they have equitable opportunities to develop the motor skills needed to engage comfortably and successfully in activities of daily living and recreation. Motor problems may be the key to fully understanding functional differences in this population. There is a vital need for services in this area across the lifespan, in order to adequately support autistic individuals through changes in their developmental context (e.g. their physical and cognitive states, social relationships, level of independence, and environments) and the demands of their day-to-day activities.

What this paper adds.

• Motor problems in autism are highly prevalent, yet underdiagnosed and poorly managed.

• An evidence-based clinical pipeline for motor problems in autism is urgently needed.

Abbreviations:

ASD

autism spectrum disorder

DCD

developmental (motor) coordination disorder

DATA AVAILABILITY STATEMENT

No data is provided for this manuscript.