Understanding Adult Autism: Facts and Statistics You Need to Know

For much of the general public, the word “autism” conjures a specific picture: A gifted but odd young boy with behavioral issues and some kind of profound, savantish knowledge, like Raymond Babbit from Rain Man or Sheldon Cooper from The Big Bang Theory and Young Sheldon. 

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Although the diagnostic criteria for autism certainly include the precocious eccentric individuals that are often portrayed in popular media, autism is a wide and encompassing spectrum. Our understanding of its various manifestations is evolving all the time. As our understanding changes, so does how we diagnose and support autistic individuals.

Autism diagnoses are typically made in childhood, but some people aren’t diagnosed until adulthood. There are several reasons that an autistic individual may not be diagnosed early in life. For example, girls are less likely to be diagnosed due to the outdated stereotypes that autism is more prevalent in boys. 

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Further, black and Latinx children and children from rural areas may also go undiagnosed due to a lack of healthcare resources, or cultural differences. A 2004 study suggests that rural populations may be more likely to tolerate divergent behaviors–including quirks that are associated with autism. 

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Childhood autism diagnoses tend to focus on developmental delays or communication differences. When considering autistic adults who were not diagnosed as children, it’s possible that those delays went unnoticed or were incorrectly diagnosed as something else. It’s important to recognize the signs of autism in adults, especially since many people may seek a diagnosis later in life.

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Signs of adult autism include: 

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• Finding it hard to understand what others are thinking and feeling
• Getting anxious about social situations
• Having difficulty making friends or preferring to be alone
• Appearing rude or blunt without meaning to
• Taking things very literally
• Misunderstanding slang, idioms or sarcasm 
• Sticking to the same daily routine and becoming distressed if it changes
• Noticing details and patterns that others may not
• Having special interests that are more intense than their peers’ interests or hobbies

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Neurodivergence––especially autism––is hard to fit into a neat box. Everyone presents a little bit differently, and even though the diagnostic criteria can be applied to a wide range of behaviors, many autistic children who are not diagnosed will grow up to be undiagnosed autistic adults. Having a deeper understanding of autism will help those people discover a key component of their identities and access vital resources and support. 

Currently, the NIH estimates that 1 in 45 adults in the United States are autistic. This includes data from all fifty states and accounts for autistic adults who haven’t been formally diagnosed. There is no evidence to suggest that the prevalence of autism in adults in the United States changes based on geography. 

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While the CDC has extensive funding and programs to estimate the number of autistic children in the United States, no such program exists for autistic adults, which means the 1 in 45 figure is an estimate. 

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As screening processes for adults improve and we deepen our understanding of autism, the estimate will likely change to better reflect the true number of autistic adults in the nation. That change will allow researchers and the general public to be more aware of how adults are impacted by autism and what types of support should be available. 

Globally, some data suggests that about .72% of the population has been diagnosed with an autism spectrum disorder, with other estimates showing a median occurrence of 1 in 100 across countries and regions. Typically, the data reveals that autism diagnoses are most prevalent in more developed nations like Japan, South Korea and the USA, with lower-income regions having lower prevalence of autism diagnoses. 

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However, there is no evidence to suggest that a country’s average income leads to more or fewer autistic individuals.

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A few different factors can explain the discrepancy between more and less-developed regions:

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• Healthcare infrastructure: Autism assessments are more accessible in North America, Europe, and Oceania. However, in developing nations, healthcare infrastructure is used primarily to treat infectious diseases instead of diagnosing and treating mental health needs. For example, around 100 million people live in Ethiopia. However, there are only about 60 psychiatrists, only one of whom specializes in child psychiatry. In this case, there simply aren’t enough experts available to correctly diagnose autism.
• Differing diagnostic criteria: There are no universal diagnostic criteria for autism spectrum disorder. Therefore, some countries have narrower definitions of autism than we do in the US. This means that someone may meet another country’s diagnostic criteria but not necessarily the country they live in. For example, Taiwan has the lowest estimated rate of autism prevalence. They offer free screenings for any child with a developmental delay. However, practitioners are much more likely to diagnose children with “developmental delay” than autism, even if autistic traits are present and noted. Because of this, autistic children in Taiwan are often misdiagnosed, which contributes to their low rates of autism. 
• Differences in autism awareness: Increased autism awareness leads to a deeper understanding of the neurotype, which leads to more people being correctly diagnosed. High autism awareness is usually restricted to higher-income countries like the United States and the United Kingdom. In other countries, there may also be fewer trained healthcare professionals and fewer government and private resources dedicated to autism awareness and research. 
• Data collection and reporting: No universal standard exists for identifying and reporting the number of autistic individuals living in a country. 

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Available information reveals that the rate of autism spectrum disorder diagnoses is rising globally, with a higher rate of prevalence in more developed nations. Still, autism may be underdiagnosed or underreported in some lower-income regions.

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Men and boys are 3 to 4 times more likely than girls and women to be diagnosed with autism spectrum disorder. This begs an interesting question: Are boys more likely to be autistic?

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Well, not really. 

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Some of this disparity can be explained by the fact that autism presents differently in women than in men, which may delay or prevent diagnosis. Women are more likely to engage in masking, for instance, which is the practice of hiding autistic traits. Because women and girls mask at high rates, their social differences may not be as noticeable to parents, educators or healthcare professionals. 

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Girls are also more likely to participate in social groups and stim in less noticeable ways. Where an autistic boy may engage in hand flapping (one of the more stereotypical autistic stims), an autistic girl may twirl her hair or fidget with her jewelry. Both hand-flapping and hair twirling are forms of autistic stimming, but one is much more likely to be pegged as autistic behavior than the other.

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The true gender gap in autism prevalence may likely be smaller than it appears. When the cultural understanding and diagnostic criteria of autism are expanded to include the autistic female experience, that gap may eventually tighten or close completely.

Historically, white children were more likely to be identified as autistic than Black or Hispanic children. This happened for several reasons: 

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• Parents are less likely to report autistic traits: A 2014 study revealed that even when a white child and a Latinx child both exhibited symptoms of autism, Latinx parents reported fewer of those symptoms.
• Lack of autism awareness amongst minority groups: Another study found that parents of ethnic or racial minorities were less familiar with the signs of developmental disorders or autism. 
• Prevalence of misdiagnosis: A study conducted by the University of Pennsylvania shows that, before being correctly diagnosed with autism spectrum disorder, some children are diagnosed with other conditions first. Amongst children who are initially misdiagnosed, Black children were over five times as likely as white children to receive a diagnosis of adjustment disorder instead of a misdiagnosis of ADHD. This suggests that autistic traits presented by Black children may be interpreted differently than traits presented by their white peers, leading to misdiagnosis that can delay or prevent an autism diagnosis.
• Medical bias: One of the largest U.S. studies on the subject found that, on average, Black children are diagnosed about three years after parents first voice their concerns to a physician. Further, Black parents often report that their physicians are dismissive, blaming behaviors on poor parenting or harmful stereotypes.

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However, the CDC reports that the racial gap in autism diagnoses is closing. In fact, autism spectrum disorder is now being diagnosed more frequently in Black and Hispanic children than in white children. These findings likely indicate improvements in autism awareness, more equitable diagnostic criteria and increased access to diagnoses in traditionally underserved communities. 

In the wake of an increase in the number of people being diagnosed with autism spectrum disorder, there’s been renewed conversation and, in some cases, renewed panic since adult autism facts and figures suggest an upward trend.

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Because of this fear, debunked theories are resurfacing and gaining traction (such as the long-disproven myth that childhood vaccines cause autism).

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So, let’s look at the data. 

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Are autism rates of autism diagnoses on the rise? 

The short answer is yes. 

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In the 26-34 year old age group, diagnoses have increased by 450% since 2011. The rate of autism in children is 1 in 36, as compared to 1 in 150 in 2000. In the 1970s, the rate of diagnoses was just 3 or 4 children out of every 10,000. 

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The long answer, however, requires a deeper understanding of why these numbers are ticking upward. Sure, a 450% increase in adult autism diagnoses makes it seem as though more people than ever are autistic. But, if we consider changing diagnostic criteria and how autistic traits present in diverse populations, we may come to a different conclusion.

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It’s worth noting that even with diagnostic trends on the rise, it’s estimated that only 2.2% of the adult population is on the autism spectrum. 

To understand the rise of autism, we must first look at its complicated history and how the diagnosis itself has changed in the last few decades.

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Autism’s storied history

Autism was first described in 1943 as “extreme aloneness” and an obsessive preference for sameness. Experts viewed the condition as an emotional disturbance with no cognitive markers. 

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In 1968, the DSM-II defined autism as a form of childhood schizophrenia marked by a detachment from reality. The DSM-III, published in 1980, first established autism as its own developmental condition, separate from schizophrenia. There were three specific diagnostic criteria, all of which must have manifested in the first thirty months of life:

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• A lack of interest in people
• Severe impairments in communication
• Bizarre responses to their environment

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The diagnostic manual was amended in 1987 to eliminate the requirement that all symptoms appear in the first thirty months and allowed for milder forms of autism to be diagnosed. However, those were considered a separate condition known as pervasive developmental disorder, not otherwise specified. Though the word “spectrum” was not yet being used, the expanded diagnostic criteria were beginning to represent the various autistic presentations. 

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The DSM-IV, released in 1997 and revised in 2000, was the first edition to define autism as a spectrum. The spectrum included Asperger’s syndrome, childhood disintegrative disorder (which was marked by severe developmental regressions) and Rett Syndrome (which was used to explain differences in movement and communication in girls). 

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Throughout the 2000s, our understanding of autism was constantly changing. There was initially a large focus on finding genetic causes and treatments for autism and its related conditions. However, after unsuccessful attempts, experts decided the venture wasn’t feasible. Ultimately, experts came to define autism as an encompassing diagnosis ranging from mild to severe. 

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In 2013, the DSM-V was published, and our current criteria for diagnosing autism were introduced, and the label “autism spectrum disorder” was born. 

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So, what does all of this mean?

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Put simply, it means that, before 1980, no one was being diagnosed with autism spectrum disorder as it exists today. Autistic traits certainly existed, but there was no freestanding and all-encompassing diagnosis to explain them. Further, early forms of the diagnostic criteria excluded much of the autism spectrum, dismissing mild and severe cases as separate conditions. The definition of autism spectrum disorder has only recently been expanded to include those cases. This means that people are being diagnosed now who may have been diagnosed with other, less accurate, conditions in decades past.

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Why do rates of autism spectrum disorder seem to be increasing?

After briefly examining the history of autism diagnoses themselves, we can conclude that the rise in autism diagnoses can at least partially be explained by the way that the diagnosis––and our understanding of it––has changed since the 1940s. 

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However, research suggests that there may be additional reasons behind the rise in autism diagnosis rates. These reasons are:

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• Expanded diagnostic criteria: As discussed, the diagnostic criteria have evolved drastically since the 1980s, which means more people now meet the threshold for diagnosis. 
• Reclassification of other conditions: Before the DSM-V was published in 2013, many people had been diagnosed with other conditions––such as Asperger’s syndrome or child degenerative disease––that are now under the umbrella of autism spectrum disorder. Further, individuals who meet the criteria for those outdated disorders are now being diagnosed with autism. 
• Increased awareness: Healthcare professionals and the general public are more aware of autism now than in the past. This means that parents and healthcare workers are more likely to recognize autistic traits in children or adults who evaded diagnosis in childhood. 
• Adult inclusivity: While the focus has traditionally been on diagnosing children, young adults are the demographic with the highest increase in autism diagnoses. With more focus placed on diagnosing autistic adults, the overall number of autistic people will inevitably increase.

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Credible research tends to agree that, yes, there are more diagnosed autistic people in the world now than in the past. Diagnosed is the keyword, though. Current trends in autism diagnoses likely just reflect our deeper and more inclusive understanding of autism rather than a true dramatic increase in autistic people.

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While there is some panic surrounding this surge of autism diagnoses, it’s likely an indication of how much progress we’re making. Having a complete and dynamic picture of what autism looks like is a vital part of supporting autistic individuals and correctly diagnosing people who historically would have fallen through the cracks.

Though the reason for the surge in autism diagnoses is hotly debated, there is one thing universally agreed upon––more adults than ever are being diagnosed with autism. A diagnosis can be life-changing and affirming, but it’s often just the first step. After diagnosis, there are many resources available for autistic adults.

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Organizations like the Association for Autism and Neurodiversity and the Autistic Self-Advocacy Network offer valuable resources for autistic adults, including help with employment, housing and day-to-day tasks. A diagnosis can unlock greater independence and a fulfilling life.

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Further, autistic adults can benefit from neurodiversity-affirming therapy. Affirming therapists specialize in autism and its daily impacts on adults. An appropriately trained therapist can help autistic individuals thrive in the face of their unique challenges. 

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How Prosper Health can help 

If you suspect you may be autistic, Prosper Health is here for you. We provide fully virtual adult autism assessments and neurodiversity-affirming therapy. 80% of our expert clinicians identify as neurodivergent or have a close connection with neurodivergence.

Our therapists incorporate evidence-based practices into all of their sessions, and they tailor their approaches to fit the unique needs of autistic adults. We also work with most major insurance companies. If you’re ready to get an assessment or if you need access to autism-affirming therapy, get started with us today!