A Beautifully Inclusive Community: The Definitions and Histories of the Neurodiversity Spectrum.

A Beautifully Inclusive Community: The Definitions and Histories of the Neurodiversity Spectrum.

When most people think of neurodivergent disorders, autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD) are probably the first to come to mind. But did you know that there are several more disorders that qualify as neurodiverse? The term neurodiverse “includes a broad spectrum of neurological disorders.”1 However, because “neurodiverse” isn’t an official medical term or condition and because its purpose is to include a diversified array of disorders, there is a broad scope of what can fall under this classification.2 Because of this, the disorders most commonly recognized as neurodiverse will be discussed.

Origins of Inclusive Terminology

It was only in the late 1990’s when the words neurodiverse, neurodiversity, and neurodivergent were introduced.3 Prior to these terms’ existence, the language used to describe or refer to individuals who had autism, ADHD, Down syndrome, learning disabilities, and other neurodevelopmental neurological disorders was othering and demeaning. More inclusive and supportive terminology was greatly needed. Judy Singer, a sociologist, agreed.4 Aside from her field of study, Singer was personally encouraged to establish more inclusive language since both her mother and daughter have autism.5 By coining a new term, Singer wanted to “promote equality and inclusion of ‘neurological minorities.’”6 It is important to note that while the term neurodiversity is mostly used to describe people who have neurodevelopmental disorders, the term technically pertains to “the diversity of all people” and “describes the idea that people experience and interact with the world around them in many different ways” rather than being used to describe one person’s experience, whether if they have a neurodevelopmental disorder or not.7

While Singer made tremendous progress in pioneering more inclusive terms, she was not the only person to coin terms for the neurodiverse community; within the following decade, Kassiane Asasumasu, a neurodivergent activist, coined the term “neurodivergent” to be used to refer to one person who is neurodiverse or to refer to the neurodiverse community.8 In a blog post, Asasumasu explicitly noted that terms like neurodivergent were not created for exclusion but to be “specifically a tool of inclusion.”9 Because Singer and Asasumasu championed for more inclusive language to be used when referring to individuals with neurodevelopmental disorders, it helped pave the way for the neurodiverse community to no longer be perceived as flawed and easily excludable.

Common Neurodiverse Disorders Recognized Today

Autism Spectrum Disorder

Autism spectrum disorder, also known as ASD and autism, is defined as “a complex developmental condition involving persistent challenges with social communication, restricted interests, and repetitive behavior;" however, autism cannot be summed up in just one definition since it varies with every individual who experiences it.10 The saying, “If you’ve met one person with autism, you’ve met one person with autism” will ring forever true since it affirms that each experience with autism is unique and should be treated as such.11 This sentiment also helps to eliminate ASD stereotypes and remind each individual with ASD that their experience is valid.

Unfortunately, many of the initial studies and ideas about autism and people who appeared to be exhibiting autistic behaviors (as it will be seen with other neurodiverse disorders), can now be seen as narrow-minded, ableist, and erroneous. Autism was initially studied in the beginning of the early 1900’s by Leo Kanner who found that some children were very smart and some even had extraordinary memory, but they also had difficulties with emotion.12 It wasn’t until the 1970’s and 1980’s when the disorder became more widely recognized, education and therapies for people with autism were initiated, and research began to discard the harsh and untrue beliefs of previous decades.13 One way this was executed was the shedding of the ideal that autism was the parents’ fault and was replaced with the belief that the disorder was instead caused by neurodevelopmental and genetic factors.14 In the last thirty years, immense progress was made in the way of advocating for further studies of autism and supporting those with the disorder.15 These progressive steps included, making educational resources for children with autism more readily available, people with autism stepping into roles where they told their own stories and/or worked to help support the autism community, and even the United States government signing acts to aid in further researching autism.16

Attention-Deficit/Hyperactivity Disorder

Sir George Fredric Still is considered to be the physician who led the “scientific starting point of the history of ADHD” since he studied children who he believed to have an “abnormal defect of moral control.”17 In other words, he saw these children’s behaviors as hyperactive and impulsive. Thirty years later, German doctors were diagnosing children who had trouble sitting still and following rules with what they began calling “hyperkinetic disorder.”18 It wasn’t until 1980 when hyperkinetic disorder became ADD; additionally, researchers wanted to separate those who were hyperactive and those who weren’t.19 Further distinction was made when what was once one disorder fishtailed into two disorders: one with hyperactivity (ADHD) and one without (ADD).20 Distinction between attention issues and hyperactivity and impulsivity issues was short lived. By 1987, the APA stated that the disorder would be known as ADHD, and in later years subtypes of ADHD were added, ending the long conversation about how hyperactivity attributed to the disorder.21

In the last three decades, there has been a surge of ADHD diagnoses, mostly because the disorder became more easily diagnosable and awareness of ADHD increased.22 While doctors and others in the field have mostly studied attention issues, hyperactivity, and impulsivity, there are a plethora of other symptoms that people with ADHD experience. Some of these symptoms include:23

  1. Disorganization
  2. Poor prioritizing and planning skills
  3. Trouble coping with stress
  4. Low frustration tolerance
  5. Trouble multitasking

Since the range of ADHD symptoms have finally begun to be more widely acknowledged in the last several years, this contributes to more people being correctly diagnosed with the disorder.

Down Syndrome

Down syndrome was first analyzed in 1862 by British physician, John Langdon Down, who predominantly helped distinguish the syndrome from mental incapacity by making it a distinct and separate disorder.24 25 While Down may have initiated studying and identifying the disorder, many of his observations and published ideas are recognized as racist and completely inaccurate.26 For instance, he stated that individuals with Down syndrome were “mongoloid” since he thought they shared similar features and levels of intellect as individuals who were labeled under Johann Friedrich Blumenbach’s “Mongolian” race.27 To make matters worse, individuals who were thought to have Down syndrome were often taken from their families at birth, ostracized, or institutionalized.28 These beliefs and practices were followed for nearly a century until 1959 when French pediatrician and geneticist, Jérôme Lejeune discovered the extra copy of chromosome 21.29 Since this discovery was linked to rational scientific studies and genetics, rather than unreasonable, mendacious racist beliefs, physicians and researchers were able to obtain a better understanding of Down syndrome. In later decades, the different types of Down syndrome would be identified. They are:30

  1. Trisomy 21 – the most common type of Down syndrome and occurs when there is an extra copy of chromosome 21.
  2. Translocation – occurs when a partial or full amount of chromosome 21 affixes to another chromosome.
  3. Mosaic – occurs when only some cells contain the usual 46 chromosomes while other cells contain 47.

Symptoms of Down syndrome can be physical, cognitive, and behavioral. Physical symptoms may present as a having a flat nose, upward slanting eyes, and shorter-than-average height, cognitive symptoms resemble underdeveloped fine motor and social skills, and behavioral symptoms are stubbornness and tantrums, attention difficulties, and obsessive and compulsive behaviors.31 Currently, there are many resources and forms of support for individuals who have Down syndrome and their families, many of them being various types of therapies.32

Tourette Syndrome

Tourette syndrome (TS) is a neurological disorder that causes tics.33 Tics can resemble sudden unwanted, uncontrollable, and repeated movements or vocalizations.34 TS was first briefly studied in the late 19th century by French doctor Gilles de la Tourette before he died in the early 20th century.35 Until the middle of the 20th century, people who were experiencing TS symptoms were considered to have a psychiatric disorder but in 1970s the disorder was redefined.36 This was because of physician Arthur Shapiro who made huge advancements in learning about TS and helped establish it as a neurological disorder.37

Tics are known to come and go over time, sometimes coming back more or less severe or as completely different than they previously were.38 The severity of tics can be because of high levels anxiety or excitement or can be less intense from being calm and relaxed.39 Examples of tics are eye movements, shoulder shrugging, repetitive throat clearing, and grunting.40 TS symptoms are often treated to be more manageable through the use of medications and therapy.41

Specific Learning Disabilities

There are a handful of learning disabilities that are often grouped together and are considered to be neurodiverse disorders. It’s common for these disorders to occur alongside ADHD and autism.


Dyslexia has its origins in the late 19th century by German professor Adolph Kussmaul and German ophthalmologist and professor Rudolf Berlin.42 Upon beginning to study the phenomenon of individuals who struggled to read, Kussmaul called the condition “word blindness” since even though these individuals could see, speak, and understand perfectly fine, they struggled reading words.43 Around the same time Rudolph Berlin was also observing people who struggled with reading, and he went on to coin the term “dyslexia” although it would be nearly another century before dyslexia replaced word blindness and when the disorder would begin to be treated rather than just studied.44 45 In 1963 it became an official learning disability and soon after more resources were made available for individuals with dyslexia.46 Today dyslexia is acknowledged as a learning disability that impedes an individual’s ability to read and which can impact spelling, writing, and comprehension skills.47 Dyslexia is classified in categories and can present in five different types.

Categories of dyslexia:48

  1. Developmental dyslexia – is genetic and may be present since birth. It contains primary and secondary dyslexia.
    1. Primary dyslexia – is genetically inherited.
    2. Secondary dyslexia – occurs because of problems with brain development during the early stages of pregnancy.
  2. Acquired dyslexia – can happen as a result of a traumatic brain injury or disease that affects the part of the brain that processes language.

Different types of dyslexia:49

  1. Phonological Dyslexia – individuals struggle sounding out words and matching sounds to symbols.
  2. Rapid Name Dyslexia – individuals struggle to rapidly name colors, numbers, and letters.
  3. Double Deficit Dyslexia – individuals struggle with two aspects of reading: naming speed and identifying the sounds in words.
  4. Surface Dyslexia – individuals can sound out words but struggle to recognize familiar words.
  5. Visual Dyslexia – individuals have a hard time recalling what they see on a page, making it hard to keep track of words and lines of text.


Dysgraphia is often confused with dyslexia since they both have to do with words.50 Nevertheless, they are two distinct disorders. Whereas dyslexia can make it difficult to learn how to read, dysgraphia affects the ability to write.51 For those who do not have dysgraphia, it’s easy to not notice how many tasks writing includes (fine motor skills, language processing, and organization, to name a few) but for those with dysgraphia, they may struggle with some or all of the tasks of writing.52 Despite being two totally separate disorders, dysgraphia was discovered amid studying dyslexia in the mid-20th century.53 Treating dysgraphia symptoms can be done through occupational therapy, using writing aids, and strengthening typing skills.54


Dyscalculia is understood as “a math learning disability that impairs an individual’s ability to learn number-related concepts, perform accurate math calculations, reason and problem solve, and perform other basic math skills.”55 Because those who have dyscalculia struggle with all types of math related information, the disorder can greatly impact daily life.56 Dyscalculia was first studied well into the 20th century when Czech researcher, Ladislav Kosc, composed an article about the disorder.57 Similar to other neurodiverse disorders, it’s thought to be caused by genetic factors and dysfunction in the part of the brain that processes numbers and math.58 There are many strategies to help make living with dyscalculia more manageable such as using calculators or scratch paper when doing math and use planning technology to help with time management and make pivoting from one activity to the next flow more smoothly.59


Even though dyspraxia may be grouped with dyslexia, dysgraphia, and dyscalculia, it’s not a learning disability but a developmental coordination disorder.60 Dyspraxia affects a person’s ability to perform motor skills and causes issues with coordination.61 In the late 1930’s, Dr. Samuel Orton studied dyspraxia and named it one of the most common developmental disorders.62 Symptoms of the disorder can resemble issues with emotional, language, and sensory skills.63 Individuals with this disorder can usually benefit from occupational therapy to help lessen their symptoms and make day to day tasks more manageable.64

What about…?

Because neurodivergence is an inclusive term, it’s often debated whether or not some disorders and illnesses count as neurodiverse. Chronic mental health illness like anxiety, depression, and PTSD and neurological disorders like Parkinson’s disease, multiple sclerosis, and epilepsy are sometimes considered neurodiverse disorders while other times they are excluded.65 66 However, neurodivergents are more likely to have comorbidities.67 For instance, individuals with autism and ADHD are more likely to have epilepsy and mental health illnesses such as different forms of anxiety (social anxiety and obsession compulsive disorder), depression, bi-polar disorder, and borderline personality disorder.68 69 Similarly, auditory processing disorder and sensory processing disorder can often occur alongside neurodivergent disorders, namely autism and ADHD, but are not technically standalone neurodiverse diagnoses.70 71 Individuals with autism are also more likely to have Prader-Willi syndrome, a disorder that causes behavior and intellectual difficulties and issues with endocrine, metabolic, and neurologic systems.72

Additionally, there are other conditions that are in the gray area of whether or not they are considered neurodiverse and are not always co-morbidities to neurodiverse disorders. These include:

  1. Irlen Syndrome – is a type of visual or perceptual processing disorder which causes difficulty in making sense of visual information.73
  2. Williams Syndrome – causes delays in cognitive development and is characterized by unique physical features and in some cases cause cardiovascular issues.74
  3. Synesthesia – causes sensory crossovers and can present in the following forms:75
    1. Auditory-tactile
    2. Day-color
    3. Grapheme-color
    4. Hearing-motion
    5. Mirror-touch
    6. Sound-color
    7. Time-space

Neurodiversity spans to include all types of neurodevelopmental and neurological disorders. While some of these disorders vary in symptoms, neurodivergent individuals usually have co-occurring neurodiverse disorders, making their experience of the world beautifully individualistic. In reviewing the histories of neurodiverse disorders, it’s evident the shared evolution that occurred between them: from when they were originally discovered, which often resulted in untrue, isolating, and grim beliefs in the late 19th and early 20th centuries, to finding adequate understandings, treatments, and therapies in the 60’s, 70’s, and 80’s, to discovering the remarkable complexities that live within the term “neurodiversity” in the last thirty years. The future of neurodiversity is bright and positive, a time when neurodivergents can finally shine and aspire toward remarkable goals.

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About the Author:

Alyssa Marchese

Alyssa Marchese is a recent graduate from the University of Colorado where she earned her bachelors in English creative writing. Alyssa was diagnosed with ADHD in her early twenties which ignited her passion for promoting the importance of mental health and neurodiversity awareness. She enjoys listening to audiobooks, knitting, and volunteering at a local animal shelter.

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