Image by Stefan Schweihofer from Pixabay

Autism spectrum conditions (ASD) and ADHD are our two most common neurodevelopment disorders, with the majority of individuals continuing to be affected into adulthood. Awareness of both conditions has increased astronomically over the last generation.

But along with this improved recognition, I’ve encountered befuddlement regarding the defining features of the two conditions. Could overdiagnosis of ASD be adding to this muddle?

Do ADHD and ASD really overlap?

One challenge to differentiating ASD and ADHD derives from them co-occurring more often than we would expect by random chance. As many as 20–30% of children with ADHD meet criteria for ASD, more than ten times the rate in the general population.

Rates of ADHD among those with ASD range from 30–80%, with most experts agreeing that a majority of individuals with ASD also qualify for having ADHD, a figure that again is an order of magnitude higher than in the general population.

Heritability, or the range in variation of a trait due to genetics, is quite high for both conditions, at around 70–80%. The genetic contribution to both conditions is polygenic with hundreds or thousands of genes each have a tiny influence on the propensity to develop the condition.

Although some researchers think that the two conditions represent different developmental manifestations of the same underlying biologic causes, most of the field sees them as two distinct conditions, and have written the diagnostic definitions to reflect that.

We diagnose individuals with ADHD when they display at least five (for adults) or six (for children) symptoms from a list of nine inattentive and nine hyperactive/impulsive symptoms. Inattentive symptoms include distractibility, not listening to others, poor follow through on projects, losing objects, making errors by ignoring details, forgetfulness, and troubles with organization.

Hyperactive/impulsive symptoms include fidgeting, restlessness, being excessively noisy, and intruding on others either verbally or physically. Symptoms must occur pervasively in multiple situations, cause distress and dysfunction, start before age 12, and can’t be due to another condition.

Over time we have expanded the concept of the autism spectrum to encompass severe autism as well as milder forms, such as Asperger’s Syndrome. In addition, the latest diagnostic revision finally acknowledged that an individual could have both ASD and ADHD, something precluded under previous rules.

Persistent deficits in social communication and interaction, occurring in multiple situations, constitute a cardinal feature of ASD. These deficits might include trouble generating verbal speech, poor reciprocity in communication (lacking the normal flow of people talking together), poor nonverbal communication, or overall deficits in managing relationships. Individuals with ASD tend to test poorly on measures of “theory of mind” — they don’t really grasp how other human brains work, what motivates others, or normal patterns of interaction.

Earlier conceptualizations of ASD required that individuals also met criteria in two other aspects of life: repetitive behaviors and abnormal interests. Repetitive, unvarying, and unusual behaviors include such actions as rocking, head banging, hand flapping, and speech patterns like repeating words or phrases (echolalia).

Abnormal interests or hobbies often involve intense devotion to tallying, counting, or categorizing objects and usually involve pulling some trait or feature out of context and focusing exclusively on that characteristic. So, rather than a broad interest in airplanes or aviation, someone with ASD might hang out at the airport to track the serial numbers on the underside of planes.

They would do so without any awareness of or interest in who designed, or built, or flies in, or relies on those planes. In this way, they would be unlike the teenager who deciphered tracking numbers to learn where Elon Musk was traveling in his private jet.

Rather than requiring that someone with ASD display symptoms in each of those three symptom clusters (communications, stereotypical behaviors, unusual interests), the current definition requires communication difficulties, along with problems with a restricted or repetitive pattern of behavior, interests, or activities.

The restricted/repetitive grouping is subdivided into four categories, and those with ASD must display behaviors that fit at least two of the four categories. Stereotypical behaviors and unusual interests make up two of those four categories.

The third category involves demonstrating extremely inflexible rigidity in routines, such as needing to get dressed in exactly the same sequence or following precisely the same path and timing to travel to a destination. The fourth category is excessive sensitivity or insensitivity to sensory input. Someone with ASD might not be bothered by sensations that others would experience as great pain, or would be overwhelmed by scents, lights, sounds, or textures that others would register as normal and acceptable.

On the surface, the ADHD and ASD criteria don’t show much overlap. One might think that would leave little room for confusion. Research suggests it is fairly easy to categorize a given behavior as due to either ASD or ADHD, with a relatively low risk for misattribution.

Studies from basic brain research and from clinical treatment also support that ADHD and ASD are distinct conditions. At the neuroanatomic level, ADHD deviations from “normal” are centered on the attentional and motivational circuits, while ASD results in more widespread disruptions of connectivity, including alterations in overall brain size and growth.

Although those with ASD tend to have small brains at birth, their brains grow dramatically in the first year at rates significantly outside of the norm.

Stimulant and other medications, as well as CBT-based approaches, can substantially reduce ADHD symptoms in a majority of individuals. In contrast, medications play only a very limited role in treating ASD. For example, low-dose antipsychotics might help some who experience agitation or aggression. Other therapies so far have shown a very restricted ability to improve core ASD deficits.

In individuals who go on to develop ASD, both the marked rate of brain growth, along with significant aberrations in eye movements (a lack of preference for looking at other’s eyes) occur during the first year of life.

This provides some of the best evidence debunking the myth that vaccine exposure contributes significantly to the development of ASD. Abnormalities in brain growth and gaze preference happen long before the administration of the MMR (around 12–15 months) and most other childhood vaccines. Measurable signs of ASD exist well before most parents become aware of their children’s communication deficits.

So why the maddening muddle of ADHD and ASD?

Although the origins of the behaviors differ in the two conditions, there are areas of superficial resemblance between ADHD and ASD symptoms. The hyperactivity of ADHD might look like the stereotypy of ASD but usually is readily distinguishable.

In contrast to the rote, repetitive motions of ASD, the kid with ADHD frenetically drums on the desktop with whatever object he gets hold of, will probably tap next on the wall, and then move on to his friend’s head, or whatever else is in range. Spontaneity, variation, and noisiness usually characterize ADHD hyperactivity, unlike the narrowly constrained movements of ASD.

ASD “unusual interests” might also be confused with ADHD hyper-focused “deep dives” into a topic or “falling down a rabbit hole” investigations of an idea. But the ADHD intellectual pursuit usually involves racing after tangential issues or delving into backstories, via a pathway marked by creativity and chaos. In contrast, ASD ASD engagement tends to involve rote, repetitive, decontextualized, superficial examinations of just one piece of the bigger picture.

Misidentifying social deficits

I think that the biggest source of diagnostic confusion between ASD and other conditions revolves around misidentifying the causes of social deficits. Many of the individuals I have met with self-diagnosed ASD describe difficulties with social interactions but don’t endorse any of the restricted/repetitive behaviors or interests that would be required to fulfill an ASD diagnosis. That alone should generate questions regarding whether ASD is an appropriate label for them.

Pervasive patterns of social deficits can arise from a number of causes other than ASD, including ADHD, social anxiety, PTSD, and personality disorders. We need to examine the nature of social deficits closely and try to discern their underlying motivations or origins, in order to accurately identify ASD social deficits and differentiate them from other disruptions of interpersonal communication.

Much of the discussion around ADHD focuses on problems with attention and cognition, and the consequent disruption of academic or career success. Yet ADHD can clearly, profoundly, and frequently impact social interactions. Those with ADHD tend to have fewer friends, more tenuous connections, divorce more often and report less satisfaction in their relationships. Indeed, many find social problems the most disruptive part of their ADHD.

But ADHD social deficits do not derive from having an inadequate theory of mind. Most of the social problems arise directly from either the inattentive or impulsive symptoms of ADHD. Individuals with ADHD don’t listen to someone speaking to them, blurt out comments, cut others off, step on toes, cut in line, show up late, or forget to respond.

When quizzed, people with ADHD know what the rules of polite discourse are, understand their culture’s rules about personal space, and are able to read the emotional expressions and body language of others. Their socially disruptive behaviors come from poor implementation of this knowledge, not from basic incomprehension of social niceties.

Social anxiety can also lead to social difficulties. People avoid interactions and act stiffly, awkwardly, or fearfully when forced into interactions. They may actively avoid eye contact. But those with social anxiety comprehend rules and roles of human interaction. They often crave social interaction. With ASD, social interactions often seem irrelevant or alien, an aspect of life that they are indifferent to.

For those with PTSD, past traumas may make one fearful or avoidant, or produce hyper-startle or other excessive reactions to social overtures. Benign acts may be perceived as threats. A number of personality disorders can also lead to pervasive social difficulties and inappropriate behaviors. Individuals with personality disorders often display distorted theories of mind, with aberrant notions regarding what motivates others, and misinterpretations of others’ behaviors.

Humans are social animals, and as such, worrying about group membership or estrangement constitutes an important strand of our psyche. Because every human is an individual, as well as a member of groups, there will always be recognizable ways that one deviates from others.

Feeling different from family or peers, and concerns about being an outsider pervasively stalk us. Increased mobility along with the dissolution of family and community ties undoubtedly amplifies these concerns. It’s not surprising that far and away the most popular book series of the last generation centered on Harry Potter, a wizard raised by (and unrecognized and unappreciated by) the muggles around him.

Humans follow fads in diagnosing mental health conditions. Tsunamis of ADHD and bipolar disorder swept over us in previous years. We are now immersed in an ASD era. That the colloquial interpretation of “on the spectrum” refers to ASD underlies this fact. After all, depression, bipolarity, schizophrenia, ADHD, gender identification, and sexual orientation, among others, all exist on a spectrum. It’s particularly ironic that the trendiest affinity groups right now are based on joining with others who don’t have an affinity for others.

I certainly respect the right of individuals to self-identify, to find their tribe, and to use the labels that they find helpful. However, those who misidentify their ASD may do a disservice to themselves and to their group. An inaccurate diagnosis can preclude helpful treatment, whether that is medication, psychotherapy, or membership in an appropriate affinity group. And if one joins a group to which one doesn’t truly belong, that can dilute or divert the power and value of the group.

Fixing Failures to Communicate

For those sorting out whether the ASD label fits, explore what your social discomfort means for you, think about its potential origins, and don’t prematurely foreclose alternative possibilities and interpretations.

Thinking about ASD should make us evaluate the word “spectrum” just as much as we examine “autism”. At its simplest, spectrum conveys that a condition exists across a broad range of severity. Some spectra traverse a range from severely affected to completely normal. We often say that “everyone acts a little ADHD” if tired enough or in a distracting enough environment.

The ADHD spectrum flows from significantly and constantly impaired to briefly and trivially disrupted. But other spectra contain only a range of dysfunction without including “normal”. The spectrum of heart attacks and schizophrenia can vary from mild to severe, but most would deem neither to overlap with “normal”. Debate continues regarding whether the autism spectrum stops at, or penetrates through, the range of “normal”.

Furthermore, “spectrum” oversimplifies. Both ADHD and ASD are clearly multidimensional, each containing multiple spectra. We break ADHD into hyperactive, inattentive, and combined subtypes, but even within inattentiveness, there are several dimensions: some people lose items all of the time, some are always late, some are constantly distracted, some miss important details in their environment — and some do all of these things pervasively. In ASD, most individuals don’t display perfect concordance in the severity of all of their various symptoms. We should be thinking of autism spectra, not an autism spectrum.

Considerations of multidimensionality lead to the topic of cross-sectionality. Not only are ASD and ADHD found together more frequently than by random chance, but they travel with a host of other traits, including left-handedness, homosexuality, and susceptibility to auto-immune disorders. How much does it dilute or confuse the concept of neurodiversity to embrace all of these dimensions?

We use words to communicate. If we don’t share a common understanding of the terms we use, then we sow confusion. We shouldn’t use ASD to indicate shyness, social anxiety, ADHD, PTSD, or personality disorders.