Autism spectrum disorders and joint hypermobility related disorders: what’s the link, and why are these conditions increasingly mentioned together?
It seems science is slowly catching up, searching along both spectrums to find the connection between autism and hypermobility spectrum disorder and other hereditary connective tissue disorders—hypermobility is often a sign of such hereditary connective tissue disorders, the best known and most commonly found being Ehlers-Danlos syndrome.
This is mostly because of the work of scientists like Dr. Emily L.Casanova and the call of patients (many in the autism community) looking for answers about the surprising overlap between autism spectrum disorders and the continuum of joint hypermobility syndrome, hypermobile spectrum disorders, and hypermobile Ehlers Danlos syndrome.
It may seem surprising that autism, a neurodevelopmental condition characterized by social impairments, would have anything in common with joint hypermobility or connective tissue disorders. That is until research showing a strong association between hypermobility and autism is considered.
But what exactly is hypermobility? This itself can be confusing as it’s a word with associations ranging from double-jointed gymnasts to disorders with serious musculoskeletal effects impacting joints, mobility, and health.
Hypermobility
Hypermobility or joint laxity means an individual has an unusual range of motion in one or more joints in their body. Joint hypermobility is therefore a descriptor not a diagnosis (Castori et al., 2017).
The term localized hypermobility syndrome is used when joint hypermobility is observed at one or two (usually less than five) joints. This condition may be genetic but could also be due to injury or trauma to the joint.
The term generalized joint hypermobility is used when joint hypermobility is present at multiple sites, usually more than five. This condition is usually congenital and sometimes a feature of genetic syndromes like hereditary disorders of the soft connective tissue. The terminology describing disorders involving joint hypermobility—especially when it comes to specific subtypes like hypermobile Ehlers-Danlos syndrome (hEDS)—may be confusing.
A Swedish study (Kindgren et al., 2021) mentions how the diagnostic criteria and international classification of Ehlers-Danlos syndrome (EDS) changed in 2017; with the authors detailing that, in their results, all Ehlers-Danlos syndrome cases could be classified as hypermobile Ehlers-Danlos syndrome (hEDS).
EDS, of which there are 13 types, are a group of hereditary connective tissue disorders which predominantly affect collagen (Demmler et al., 2019). The most common type is the hypermobile variant (hEDS). According to research hEDS may be underdiagnosed and poorly understood by practitioners, leading to patients waiting for many years before finally receiving an accurate diagnosis.
Study researching the link between autism and Ehlers-Danlos Syndrome
The retrospective study mentioned above (Kindgren et al., 2021) found a significant association between attention deficit hyperactivity disorder (ADHD) or autism spectrum disorder (ASD) and hEDS. The authors go on to suggest that children with EDS or hEDS may require routine screening for neuropsychiatric symptoms.
Finding a link like this may prompt parents to ask whether joint hypermobility is a symptom of autism. They may wonder about the need to screen any child with an unusual range of movement in joint(s) for ADHD and/or ASD. It is important to note that hypermobility does not always indicate an autism risk, and it is not always a symptom of a genetic connective tissue disorder. Hypermobility may be caused by environmental factors, it often runs in families, and sometimes hypermobility may be advantageous in athletic pursuits.
Parents should, however, be aware that rates of hypermobility are particularly high in adults with neurodevelopmental diagnoses (Eccles et al., 2014). Therefore, when in doubt, parents should consult with a doctor with knowledge of the clinical presentation of both autism and generalized hypermobility spectrum disorder. Joint laxity may be indicative of serious heritable conditions like hEDS, which is still poorly understood by many physicians.
Similarities in presentation of ASD and hEDS
A review of the similarities in the clinical presentation of ASD and Ehlers-Danlos Syndrome hypermobility-type (as it was known before classification of the condition changed) used the case of a 12-year-old boy as illustration (Baeza-Velasco, 2016). In this case the boy’s autistic traits overlapped or could be explained by the presence of a connective tissue disorder like hEDS.
According to information from the child’s medical records, he displayed many of the core characteristics/symptoms associated with autism: as a toddler he failed to respond to his name, he struggled with eye contact, and he displayed stereotypic behaviors like frequent handwashing. Mention is also made of the child’s preference to spend his time lying down rather than playing at the park, his preference for adult company, and sensory difficulties like hypersensitivity (Baeza-Velasco, 2016).
The authors mention that the child was referred to the Department of Rehabilitation Medication due to motor difficulties which started in early childhood. These included: toe walking, little stability when sitting, clumsiness, and challenges in learning to ride a bike and dress himself.
At the time of his consultation at the Department of Rehabilitation Medication, the patient’s most challenging symptoms seemed to be:
- Severe generalized pain
- Chronic fatigue
- Gait problems
The boy scored high on the test for joint hypermobility, he had a record of frequent sprains, thin skin prone to scarring, and proprioceptive dysfunction. Although milder, some of the impairments manifested in others in the child’s family, suggesting a genetic component. The case emphasizes the similarities in presentation of autism and connective tissue disorders (Baeza-Velasco, 2016).
The difficulty of distinguishing between the two conditions, with overlapping symptoms, may be especially important for doctors when diagnosing a child. The authors (Baeza-Velasco, 2016) discuss how some characteristics seen in ASD may be explained by heritable disorders of connective tissue (HDCT). To illustrate, they delved into research about motor difficulties in hEDS and how clumsiness, slowness, and preference for lying down (of an individual with the condition) may lead to social rejection, especially at school.
These discussions bring forth important considerations about autistic traits in children diagnosed with hypermobility related disorders. Do the sensory and motor difficulties associated with such disorders lead to social withdrawal or isolation impacting social communication, or is there a link between ASD and hypermobility spectrum disorders predisposing individuals to both conditions?
The connection between the two conditions
As autism is frequently diagnosed by a developmental pediatrician or child psychiatrist, and connective tissue disorders and hypermobility-related disorders by a rheumatologist or even geneticist, the association between the two conditions did not receive much attention until recently. So even though a pediatrician specializing in neurodevelopmental conditions may test for joint laxity during an initial screening for autism, unless the problem is severe the symptom may be ascribed purely to autism (Casanova et al., 2020).
Preliminary research from Casanova et al. (2020) found more than 20% of mothers with EDS/hypermobility spectrum disorders reported having autistic children—this percentage is significant when comparing it to the similar 19% seen in mothers with autism. The authors suggest an interesting possibility, perhaps some forms of autism are hereditary connective tissue disorders. The authors mention their laboratory’s commitment to researching the possibility to help improve the lives of those affected by chronic illness (like certain hypermobility spectrum conditions). For many with hypermobility related disorders, pain is probably one of the most urgent issues to address.
Chronic pain
Because of the communication deficits in autism we may not recognize and understand pain experienced by individuals with autism. For those with joint hypermobility disorders, pain may be due to laxity or the tendency to dislocate the hypermobile joint. Joint hypermobility means more flexibility but also a predisposition to pain and trauma as the tissue is more fragile.
Research (Hershenfeld et al., 2016) suggests higher rates of pain symptoms in individuals with Ehlers-Danlos syndrome when the condition co occurs alongside psychiatric conditions. Furthermore, mast cell activation syndrome (frequently linked to painful conditions) may be another link between ASD and hypermobility spectrum disorders.
Providing an overview of the link between ASD and hypermobility related disorders, the authors (Baeza-Velasco et al., 2018) suggest disseminating information about the potential link between the two conditions may be beneficial in clinical contexts. It could encourage awareness of pain and pain-related symptoms in a group of people “ in which it is extremely challenging to screen for and manage pain.” (Baeza-Velasco et al., 2018)
Another important aspect of researching the association between hEDS and autism is the particular way both conditions affect females.
Masking, autism and hEDS
Autism is underdiagnosed in girls; there is increasing evidence of a camouflaging or masking effect among females on the spectrum. This may contribute to the delay in recognizing challenges and hinder provision of appropriate support (Wood-Downie et al., 2021).
Autism may be even more prevalent in those with generalized hypermobility syndrome or EDS if one considers these disorders occur more frequently in women who may be masking their autistic traits. More studies are necessary but researchers are uncovering more data suggesting the outdated idea of EDS, and other joint hypermobility syndromes, being rare disorders only affecting the musculoskeletal system and soft tissues should be revisited (Demmler et al., 2019).
Dr. Casanova, Research Assistant Professor at the University of South Carolina, is one of the research pioneers advocating for more studies concerning Ehlers-Danlos syndromes/Hypermobility spectrum disorders in the autism population. Her team’s research (Casanova et al., 2020) found results reinforcing concepts of an etiological association between autism and generalized hypermobility.
Dr. Casanova et al., (2018) used an online survey finding:
- Autistic women with generalized joint hypermobility reported more immune (and endocrine-mediated) conditions than those without generalized joint hypermobility
- Autoimmune conditions featured prominently in the autism/generalized joint hypermobility group
Final thoughts
Furthermore, the research (Casanova et al., 2018) also explains how connective tissue regulates the immune system. Perhaps joint hypermobility will become a red flag in diagnosing females on the spectrum. While social communication impairments could be camouflaged, the presence of joint hypermobility and connective tissue disorders should alert clinicians in various specialties to the possibility of neuropsychiatric conditions.
Alternatively, awareness should be promoted of the possibility that a child may be misdiagnosed as being on the spectrum because of a condition like hEDS’s symptoms overlapping with those found in ASD. Sensory difficulties, preference for lying down, and stereotypic movements could be explained by joint hypermobility or connective tissue disorders. An accurate diagnosis means symptoms can be treated appropriately, and this is essential for kids on the spectrum whose joint hypermobility could contribute or cause chronic pain.
Austic children may have severe difficulty communicating about pain and related symptoms, often leading to self-injurious and other challenging behavior. In some cases joint hypermobility may be the only clue that a child on the spectrum has a hypermobility related disorder, the only clue that a child is suffering with little means to let us know they’re in pain.
References:
Baeza-Velasco, C., Cohen, D., Hamonet, C., Vlamynck, E., Diaz, L., Cravero, C., Cappe, E., & Guinchat, V. (2018). Autism, Joint Hypermobility-Related Disorders and Pain. Frontiers in psychiatry, 9, 656. https://doi.org/10.3389/fpsyt.2018.00656.
Baeza-Velasco, Carolina & Hamonet, C. & Baghdadli, Amaria & Brissot, Regine. (2016). Autism Spectrum Disorders and Ehlers-Danlos Syndrome Hypermobility-Type : Similarities in clinical presentation.. Cuadernos de medicina psicosomática y psiquiatria de enlace. (in press).
Casanova, E. L., Baeza-Velasco, C., Buchanan, C. B., & Casanova, M. F. (2020). The Relationship between Autism and Ehlers-Danlos Syndromes/Hypermobility Spectrum Disorders. Journal of personalized medicine, 10(4), 260. https://doi.org/10.3390/jpm10040260.
Casanova E.L., Sharp J.L., Edelson S.M., Kelly D.P., Sokhadze E.M., Casanova M.F. (2020) Immune, autonomic, and endocrine dysregulation in autism and Ehlers-Danlos syndrome/hypermobility spectrum disorders versus unaffected controls. J. Reatt. Ther. Dev. Divers.2:82–95.
Castori M, Tinkle B, Levy H, Grahame R, Malfait F, Hakim A. 2017. A framework for the classification of joint hypermobility and related conditions. Am J Med Genet Part C Semin Med Genet 175C:148–157.
Demmler, J. C., Atkinson, M. D., Reinhold, E. J., Choy, E., Lyons, R. A., & Brophy, S. T. (2019). Diagnosed prevalence of Ehlers-Danlos syndrome and hypermobility spectrum disorder in Wales, UK: a national electronic cohort study and case-control comparison. BMJ open, 9(11), e031365. https://doi.org/10.1136/bmjopen-2019-031365.
Eccles JA, Lodice V, Dowell NG, Owens A, Hughes L, Skipper S, et al. (2014) Joint hypermobility and autonomic hyperactivity: relevance to neurodevelopmental disorders. Journal of Neurology, Neurosurgery & Psychiatry 85:e3 10.1136/jnnp-2014-308883.9.
Hershenfeld, S. A., Wasim, S., McNiven, V., Parikh, M., Majewski, P., Faghfoury, H., & So, J. (2016). Psychiatric disorders in Ehlers-Danlos syndrome are frequent, diverse and strongly associated with pain. Rheumatology international, 36(3), 341–348. https://doi.org/10.1007/s00296-015-3375-1.
Kindgren, E., Quiñones Perez, A., & Knez, R. (2021). Prevalence of ADHD and Autism Spectrum Disorder in Children with Hypermobility Spectrum Disorders or Hypermobile Ehlers-Danlos Syndrome: A Retrospective Study. Neuropsychiatric disease and treatment, 17, 379–388. https://doi.org/10.2147/NDT.S290494.
Ratto, A. B., Kenworthy, L., Yerys, B. E., Bascom, J., Wieckowski, A. T., White, S. W., Wallace, G. L., Pugliese, C., Schultz, R. T., Ollendick, T. H., Scarpa, A., Seese, S., Register-Brown, K., Martin, A., & Anthony, L. G. (2018). What About the Girls? Sex-Based Differences in Autistic Traits and Adaptive Skills. Journal of autism and developmental disorders, 48(5), 1698–1711. https://doi.org/10.1007/s10803-017-3413-9.
Wood-Downie, H., Wong, B., Kovshoff, H., Mandy, W., Hull, L., & Hadwin, J. A. (2021). Sex/Gender Differences in Camouflaging in Children and Adolescents with Autism. Journal of autism and developmental disorders, 51(4), 1353–1364. https://doi.org/10.1007/s10803-020-04615-z.
