What is comorbidity in ASD?
The co-occurrence of two or more diagnosed conditions in the same person is called comorbidity. An estimated 75% of children and young adults on the spectrum are diagnosed with at least one comorbid condition in their lifetime.1,2 In fact, in a 2010 comparative study, researchers found that 95% of youth on the spectrum had at least three comorbid disorders and 75% had at least five.3 It is apparent that individuals on the spectrum have higher levels of comorbidity, especially psychiatric and physical conditions, compared to their neurotypical peers.4,5 However, scientists have yet to discover exactly why this is the case as research on co-occurring conditions specific to ASD is a relatively new discipline.6,2 Continued research in the field is necessary because these conditions often exacerbate ASD traits, influence the timing and accuracy of autism diagnosis or misdiagnosis, and affect quality of life.
The most diagnosed comorbid conditions in autistic individuals are anxiety, depression, attention deficit/hyperactivity disorder (AD/HD), gastrointestinal issues and epilepsy.7,8,5 Comorbid conditions vary widely in severity and manifestation but are most often included in one of the following groups:
Classic medical/physical problems, which include sleeping disorders, epilepsy and gastrointestinal issues;
Psychiatric disorders like anxiety, attention deficit/hyperactivity disorder (AD/HD), depression, obsessive-compulsive disorder (OCD), and bi-polar disorder;
Developmental issues, including any kind of language impairment or delay and intellectual disabilities; and
Genetic conditions, such as tuberous sclerosis and fragile X syndrome.9,10
How do comorbid conditions affect people on the spectrum?
As mentioned before, the vast majority of people with ASD will be diagnosed with at least one comorbid condition during their lifetime.11,3 It is important to understand the impacts of these diagnoses, because most conditions that co-occur with autism have potential to seriously affect well-being and quality of life.9 Some comorbid symptoms can cause much more harm than an autism diagnosis, especially conditions like depression, epilepsy or anxiety, which can have lasting effects.12
Comorbid conditions also make it difficult to diagnose ASD, and vice-versa. Many symptoms of co-occurring conditions overlap with those of ASD, like sensory processing issues, poor social skills, trouble focusing, and stimming. This sometimes results in a diagnosis for mental health issues instead of ASD. Similarly, autism can be screened for in young children and infants while depression, anxiety, and epilepsy typically begin to manifest around age eight and, therefore, are understood as evolving symptoms of ASD and not addressed on their own.13,11 Even further, diagnoses for psychiatric conditions are not often tailored to individuals on the spectrum and require the patient to complete an interview process or personal checklist. This presents a real problem for autistic individuals with intellectual disabilities or impaired language abilities. A diagnosis for autism can be equally as difficult for individuals with verbal or intellectual disabilities.2,13 Researchers are already creating autism-specific tools for diagnosis of the most prevalent comorbid conditions.14
Beyond all of this, it is important to remember that because many individuals on the spectrum communicate differently to the general population, comorbid conditions may not look the same as they do in a neurotypical person. Keep this in mind when you are assessing yourself or your child on the spectrum.
As this new field of study continues to grow, our understanding of the possible causes, effects, and treatments for comorbid traits and ASD will keep expanding.15 For example, connections between genetics, epilepsy, and ASD are already beginning to advise new screening processes based on family history/relation and age.16,17 As our understanding of these conditions and symptoms increases, researchers will be able to create more specific and targeted therapies and screenings for individuals on the spectrum and their families.
In the meantime, it is a good idea to keep up to date with current research on topics like these. A web search every now and again can help you stay on top. There are a few links below to websites that have recent ASD research and are updated with new content frequently.
More importantly, however, try to keep track of yourself or your child with ASD. If you or your child have ASD, keep a close eye on emotional and physical well-being, stay up to date with family health history and continue regular assessments to ensure no conditions are going untreated.
- An in depth overview of Medical Comorbidities and ASD from Autism Research Institute
- Parent advice from Autism Research Institute
- Common Comorbid Conditions in ASD (LINK TO POST #9)
 Research and Development Disabilities, 28, pages 341-352 (2007)
 Autism Research Institute, Overview: Medical Comorbidities and ASD, (2021)
 Journal of Autism and Developmental Disorders, 40, pages 1361-1370, (2010)
 The Permanente Journal, 21, pages 16-088, (2017)
 Frontiers in Psychiatry, 10:617, (2019)
 Research in Autism Spectrum Disorders, 7:10, pages 1228-1233, (2013)
 Research in Autism Spectrum Disorders, 7:12, pages 1595-1616, (2013)
 Research in Autism Spectrum Disorders, 6;1, pages 406-412, (2012)
 Centers for Disease Control and Prevention, Epilepsy fast facts
 Centers for Disease Control and Prevention, What is fragile X syndrome?
 Journal of Autism and Developmental Disorders, 48;8, pages 2663-2676, (2010)
 Autism Research Institute, Autism and Depression, (accessed 2021)
 Neuropsychiatry, 3;2, pages 233-243, (2013)
 Spectrum Viewpoint, Why we need screens for depression in people with autism, (2018)
 Brain and Development, 32;9, pages 731-738, (2010)
 Spectrum News, Epilepsy in family members raises risk of autism, (2016)
 Neurology, 87;2, pages 192-197, (2016)