The Symptoms and Signs of High-Functioning Autism in Adults

October 4, 2023   •  Posted in: 

What is autism?

The term “autism” was first introduced in 1943 by the psychiatrist Leo Kanner who was studying the behavior of children. Today, autism is known to be a lifelong developmental disability affecting how people communicate and interact with the world.

Current estimates range between 1-in-44 to 1-in-100 people who are on the autism spectrum. That’s at least five million people in the US, or 1.5% of the population. Many believe the prevalence of autism may be much higher.

Autism is also referred to as Autism Spectrum Disorder (ASD), or Autism Spectrum Condition (ASC). These terms acknowledge the broad nature of the diagnosis, although it remains listed as a single diagnosis within the Diagnostic and Statistical Manual of Mental Health (DSM-V).

Previous diagnoses, such as Asperger Syndrome or Pervasive Developmental Disorder, are no longer used, and now fall under the umbrella term of autism. However, those who have received a diagnosis of Asperger syndrome, in particular, may choose to continue referring to their condition by this name.

“Disorder” is a term applied by the world of psychiatry that is not always used by those within the autistic community and their advocates. Instead, autism is viewed as part of neurodiversity: the natural diversity in human thinking, and experience, with varying strengths, differences, and weaknesses. Other neurodivergent conditions include ADHD, obsessive-compulsive disorders (OCD), dyslexia, dyspraxia, dysgraphia, dyscalculia, dysnomia, Tourette’s Syndrome, and developmental speech impairments.

What is the autism spectrum?

Autism is a spectrum condition, meaning it affects people in different ways. As with any group of people, autistic people have a range of strengths and difficulties that may or may not be shared with other autistic people. How individuals experience characteristics of their autism will be different from person to person.

“If you’ve met one person with autism, you’ve met one person with autism.”

Dr Stephen Shore
(An autism advocate who is on the spectrum)

What causes autism?

There are thought to be several causes of autism, and these are still being researched. Scientists have established that it is mainly genetic. There are many genes involved, and environmental factors may also play a role[1]. The evidence has not yet established why autism commonly occurs alongside ADHD, epilepsy, and a range of other conditions.

Reports of an “autism epidemic” are unfounded. Instead, the expansion of diagnostic criteria combined with increased awareness has led to steadily increasing rates. The myth that autism is caused by vaccines has been debunked in multiple studies dating back to 1999[2].

What is high-functioning autism?

Some autistic people have significant support or care needs. They may be non-speaking, experience developmental delay, and be more likely to also have other diagnoses, including intellectual disability.

High-functioning autism refers to those on the spectrum with little or no support, nor care needs. Those in this category may have typical speech, language and intellectual skills but difficulties with social/conversation skills, narrowly focused interests, and wordy, pedantic communication, for example.


What are the signs of autism?

Because autism is a spectrum condition, the range of difficulties autistic people may experience is broad.

A formal autism diagnosis requires a person to experience differences in two key areas:

  • Social interactions, including verbal and nonverbal communication
  • Repetitive, restricted or ritualistic behaviors (often called “stimming”), including resistance to changes and/or intense interests

Autistic adults report a number of different difficulties across many areas of their lives. These can apply to adults who have been diagnosed with autism as well as adults who are beginning to consider whether they might be autistic. Some choose to self-diagnose.

If you want to know whether you or an adult you know might be showing some of the signs of autism, look out for some of the following:

  • Difficulty interpreting verbal and non-verbal language, such as gestures or tone of voice or sarcasm
  • Taking things literally and not understanding abstract concepts
  • Needing extra time to process information or answer questions
  • Repeating what others say to them
  • Difficulty reading other people
  • Difficulty recognizing or understanding others’ feelings and intentions
  • Difficulty expressing their own emotions
  • Appearing to be insensitive
  • Seeking out time alone when overloaded by other people
  • Not seeking comfort from other people
  • Appearing to behave strangely or in a way thought to be socially inappropriate
  • Finding it difficult to form friendships
  • Experiencing the world as an unpredictable and confusing place
  • Preferring to have routines with predictable outcomes, such as traveling the same way to and from school or work, wearing the same clothes every day, or eating exactly the same food for breakfast
  • Repeating movements such as hand flapping, rocking, or the repetitive use of an object such as twirling a pen or opening and closing a door
  • Finding these types of repetitive behaviors calming and enjoyable
  • Responding to a change to routine by becoming very distressed or anxious
  • Difficulty adjusting to big events (such as the holiday season or changing schools), and/or something simpler like a bus detour
  • Over- or under-sensitivity to sounds, touch, tastes, smells, light, colors, temperatures or pain, which can cause anxiety or even physical pain
  • Preferring to avoid physical contact due to discomfort, which can be misinterpreted as being cold and distant
  • Avoiding everyday situations because of sensitivity issues
  • Finding schools, workplaces and shopping centers particularly overwhelming as they cause sensory overload
  • Intense and highly focused interests, often from childhood, which can change over time or be lifelong
  • Becoming an expert in a special interest and wanting to share knowledge
  • Gaining huge amounts of pleasure from pursuing interests, and seeing them as fundamental to wellbeing and happiness
  • Being so highly focused on particular topics or activities that other aspects of life are neglected
  • Experiencing extreme anxiety, particularly in social situations, or when facing change
  • Experiencing anxiety to such a degree that it impacts quality of life
  • Difficulty recognising and regulating emotions
  • Experiencing a meltdown when overwhelmed (meltdowns are very intense and exhausting experiences that happen when someone becomes completely overwhelmed by their current situation and temporarily loses control verbally (eg shouting, screaming, crying) or physically (eg kicking, lashing out, biting) or both)
  • Experiencing a shutdown when overwhelmed, which appears less intense than a meltdown to the outside world but can be equally debilitating – e.g. an autistic person going quiet or “switching off”
  • Restrictive eating patterns

Adapted from the National Autistic Society guidance


Why is autism missed in some people?


Women and girls, in particular, are under-diagnosed with autism. This is for a number of reasons, including that autism is historically thought of as more prevalent in males, and because women and girls are more adept at ‘masking’ the signs of autism using camouflaging and coping strategies.

Symptoms experienced by women and girls are usually more internal than external, and they can easily be confused with anxiety or depression. The DSM-5 acknowledges that “girls without accompanying intellectual disability or language delays may go unrecognized, perhaps because of subtler manifestation of social and communication difficulties.”

Ethnicity and background

Non-white children, and those from rural areas or disadvantaged socioeconomic backgrounds are also often diagnosed later or missed altogether. Again, there are a number of reasons for this discrepancy, many based in the structural inequalities within our society.


One reason that the prevalence of autism has been increasing is because of the growing awareness among the general population and the scientific community.

One example of this is Greta Thunberg. The environmental activist is autistic (she identifies with the Asperger Syndrome diagnosis), and she speaks about her condition as well as her views on the climate crisis. One study[3] looked at the number of times Asperger syndrome was searched as a term on Google after the UN Climate Summit, and found it was 254% higher than predicted. The researchers concluded that:

“Positive media coverage of influential figures with psychiatric diagnoses may have unique power to connect individuals with the same condition (Lippert et al. 2019). These influential figures can dramatically increase public awareness around specific topics (Torgerson et al. 2019; Ayers et al. 2013), such as Asperger syndrome, which in turn increases the likelihood that individuals needing help will seek it (Lee 2019).”

Coping strategies

Adults with autism are more likely to be recognized and supported if they also have significant support or care needs, whereas those with fewer needs tend to be overlooked. Some people with autism fly under the radar until a tipping point at which their coping strategies stop working. In other words, it isn’t possible to diagnose autism until the point at which social communication demands exceed the person’s capacities. At this stage, the person might begin to question why they are struggling with social communication and behavior in a way that is different to friends or family.


Some autistic people are incorrectly diagnosed with other psychiatric disorders. Symptoms of autism do overlap with those of other conditions, such as personality disorders, psychoses, anxiety disorders, obsessive-compulsive disorders (OCD) and intellectual disability. Medical professionals who are not familiar with autism may mistake signs and symptoms for those of other conditions.

Likewise, disorders such as those listed above may be present as well as autism. If they are diagnosed first, the autism may be missed.

A recent study[4] looked at how many mental health diagnoses are also present in the autism population. It found that 20% of autistic people also had anxiety disorders, 11% had depressive disorders, 9% had OCD, 5% had bipolar disorders, and 4% had schizophrenia spectrum disorders. This suggests that psychiatric issues are more common in people with autism than the neurotypical population.

Similarly, the symptoms of ADHD are similar to those of autism, but a diagnosis of ADHD is likely to be made before autism.


Why pursue a diagnosis of autism in adulthood?

There are many reasons why people pursue a diagnosis of autism, and this can be hugely beneficial. Many professionals worldwide are now trying to identify the “lost generation” of adults with autism, as this is crucial for adequate planning of treatment and global case management.

1. Accessing the right support
It’s virtually impossible to provide the right support and care to the people who need it when they are not known to the health system. Over one-third of autistic people have serious mental health issues, and many autistic people are being failed by mental health services. Diagnosis will give you access to professionals who can help. Other support may be accessed, too, such as disability benefits, or academic and job inclusion adjustments.

2. Understanding why
A common response to diagnosis is to feel relieved that there is a reason for the difficulties people have been experiencing, often for their entire lives.

3. Identity and community
Putting a name to a condition can help people to feel less alone. The autism community is a vast and welcoming one, and newly-diagnosed autistic people can feel a huge sense of relief at finding a group of people who understand them.

4. Treatment
Although there is no ‘cure’ for autism, there are treatments that can help autistic people. Examples of helpful treatments include speech and language therapy and occupational therapy.

Similarly, getting a clear picture of autism and any other conditions that may also be present makes it easier to treat those other conditions, too, in a way that accounts for autistic preferences.

On the flipside, some autistic traits may look like symptoms of other conditions, such as eating disorders or OCD. If you’re being treated for those (often unsuccessfully), an autism diagnosis gives a much clearer picture of what those symptoms really are and why they are actually useful coping strategies.

If you have noticed you have some of the signs and symptoms of autism, and would like to explore whether this diagnosis might be true for you, contact The Center • A Place of HOPE. An award-winning mental health treatment facility, we are pioneers of the Whole Person Care approach, meaning that we look at everything you’re experiencing in your life to find the right treatment program for you. Contact us today – call 1-888-771-5166.

[1] Mandy W, Lai MC (March 2016). “Annual Research Review: The role of the environment in the developmental psychopathology of autism spectrum condition”. Journal of Child Psychology and Psychiatry, and Allied Disciplines. 57 (3): 271–292. doi:10.1111/jcpp.12501
[2] Gerber JS, Offit PA. Vaccines and autism: a tale of shifting hypotheses. Clin Infect Dis. 2009 Feb 15;48(4):456-61. doi: 10.1086/596476
[3] Hartwell, M., Keener, A., Coffey, S. et al. Brief Report: Public Awareness of Asperger Syndrome Following Greta Thunberg Appearances. J Autism Dev Disord 51, 2104–2108 (2021).
[4] Fusar-Poli, L., Brondino, N., Politi, P. et al. Missed diagnoses and misdiagnoses of adults with autism spectrum disorder. Eur Arch Psychiatry Clin Neurosci 272, 187–198 (2022).

Dr. Gregory Jantz

Pioneering Whole Person Care over thirty years ago, Dr. Gregory Jantz is an innovator in the treatment of mental health. He is a best-selling author of over 45 books, and a go-to media authority on behavioral health afflictions, appearing on CBS, ABC, NBC, Fox, and CNN. Dr. Jantz leads a team of world-class, licensed, and...

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