Autism & ADHD—how do we differentiate similar traits?

Up to 80 percent of autistics also meet the criteria for ADHD, and up to 50 percent of persons with ADHD meet the criteria for autism. This significant overlap was not known in the past, and previously, a lot of incorrect assumptions were made about both conditions.^[1]ASD and ADHD Comorbidity: What Are We Talking About? (Hours, Recasens & Baleyte, 2022)

Psychometrics are very helpful in assessment, but they have their limitations and so it is important that a clinician use an approach with three distinct elements.

1. Clinician experience
2. Patient’s experience of their traits or symptoms
3. Evidence-based psychometrics

It is also important to understand that a psychometric alone can not determine if a person has a condition. The SAAST does a good job of identifying ADHD, but because both ADHD and autism share a number of executive skill challenges, sometimes a test can identify a person (like myself) as having ADHD when, in fact, I do not.

Autism and ADHD have many overlapping traits due to shared executive skill challenges. One main difference is the level of a person’s experience with inattention.

My most significant executive skills challenges are patience and losing things. I have very few challenges with my attention. My focus is very good, to the point that people throughout my life have asked how I focus so intently. Honestly, I have just always been this way. My parents used to joke that I would leave my baby at the store due to focussing on shopping. I never forgot the baby, but I often left my groceries as I was so enamoured with my son.

So it is important to look at why a person answers the questions the way they do to be able to make a definitive diagnosis.

Below are the reasons behind why Kendall (my best friend and editor at Embrace Autism), who has ADHD, and myself, who does not have ADHD, answer the same questions.

Test answers

1. I find that I make careless mistakes in work, in school, or in other activities; or I have trouble paying attention to details.

Natalie:

Somewhat

First, I don’t like that there are two completely separate questions.

a1. Careless mistakes: This is something I do a fair amount in my writing but not in my head. As I have dyslexia, I have problems with spelling and also with switching letters. I do not make careless mistakes in other areas. So in spelling, yes, but not in other things or other areas. My level of interest is not a factor in how much I make errors.

a2. Work, in school, or in other activities:

b. Trouble paying attention to details: I am a big-picture person, so I naturally pay attention to the forest and not the trees. If I need to, I can switch, but that takes a lot more brain power. That is something we know is a skill of autistics: they can switch between bottom-up or top-down processing. I have trouble paying attention to details when I am very tired or when the information is very high level in a field I lack knowledge of.

Kendall:

Moderately

a1. Careless mistakes: The less interested in something I am, the more mistakes I will make. I have to pay significant energy to not overlook things.

a2. Work, in school, or in other activities: It happens across different activities.

b. Trouble paying attention to details: If it is something I am not interested in, it is just about impossible. If someone is explaining some aspect of something to me, it is so uninteresting that it does not even go in my head. I just glaze over. For example, if I go to the accountant and he starts explaining something about a form—I tell him I don’t want to understand it and that there is no point in explaining it to me. I guess I don’t want to spend resources on something that is so uninteresting to me.

Differences: My errors are errors mostly due to spelling and mild dyslexia, while Kendall’s errors correlate with his interest. The more interested I am in something, the more mistakes I will make due to excitement. Boredom lies behind Kendall’s errors.

I lose interest when the information is way outside of my breadth of knowledge. Kendall has a hard time paying attention when he is not interested in the topic.

2. I tend to fidget with my hands or feet, or I squirm in my seat.

Natalie:

Somewhat

I fidget or stim to calm myself. I recall when I was stressed and driving, my son said, “Mom, you are doing that thing with the keys”. Moving while trying to focus on a task is distracting for me.

Kendall:

Very much

Sometimes it is calming, sometimes it is focusing, and sometimes it is feeling antsy. I can be sitting at a table and spinning a glass or pulling a label off a bottle—I can’t just sit there. I am always on the move; when talking on the phone, for example, I am walking around as I can not just sit there.

Research on stimming is still developing. A landmark 2015 study of hyperactive fidgeting amongst children with ADHD provides the most relevant proof of the power of fidgeting, or stimming. Researchers measured the physical movement of 44 children with ADHD as they performed a test of their focus. They found that more physical movement was generally associated with better performance in the task at hand. Interestingly, this advantage was unique to the children with ADHD. Those without ADHD performed better when they moved less.^[2]A trial-by-trial analysis reveals more intense physical activity is associated with better cognitive control performance in attention-deficit/hyperactivity disorder (Hartanto et al., 2015)

Differences: Kendall uses stimming to focus, as well as calm himself. I exclusively use stimming to calm myself.

3. I often miss what is being said to me in conversations.

Natalie:

Somewhat

I find most everything interesting. I only miss things in conversations if I am distracted by something else, like anxiety, or something that I have to get done immediately, but that is not a common occurrence. My brain hierarchies information, so it stays very focused on the biggest thing. If I am anxious, then it wants to stay focused on the anxiety.

Kendall:

Moderately

“Say that again?” Yes, I do. It happens because I am thinking about something else. A completely unrelated thought pops into my mind, and that absorbs my attention. I was thinking about a pocket knife, that I need to sharpen a pencil, and oh yes, my sandpaper is in the closet, as I want to do a drawing. During talking, something may be said that is barely related, and it triggers a memory of something else.

Differences: I will lose track of something being said because I am engaged in something else or I am distracted by anxiety. Kendall’s attention just wanders.

4. I prefer to run about or climb on things, even when I know it doesn’t fit the situation.

Natalie:

Not at all

Absolutely not. That is against the rules, and we don’t break the rules. My parents were called in to school for me being too good.

Kendall:

Very much

As a child, for sure. But I don’t now as an adult. As a child always got a “lack of self-control”, and I never knew what it was that I was doing.

Differences: Kendall engaged in this as a child, I never did. Traits we had as a child and no longer have as an adult are significant for diagnosis.

5. I find it difficult to organize my tasks and activities.

Natalie:

Not at all

Absolutely not. My brain hierarchies things and organizes everything into place, and then I just get going.

Kendall:

Moderately

If there are too many things, then I have a really hard time figuring out what to do. My brain tells me everything at the same time, and then I freeze.

Differences: My brain naturally organizes things. Kendall’s brain gets overwhelmed with more than one task at a time, because his brain does not know which tasks to prioritize.

6. I am often “on the go”; as if driven by a motor.

Natalie:

Not at all

I do not know what this really means. If it means that I always have a ton of work and duties or things I want to do, then yes. Intellectually I am very efficient.

Kendall:

Very much

If I am talking the phone, I am walking around from room to room.

Differences: I don’t need to be moving around—Kendall does.

7. I tend to lose things that I need for school or work.

Natalie:

Very much

I lose things all the time. Mayhem! I have learned to overcome a fair amount of this by learning to put things in the correct places, and also to have my assistant help me keep track of things.

Kendall:

Very much

I constantly lose things. I spend a lot of time walking around this place looking for stuff.

Differences:  This is a weakness for us both.

8. I can’t help but give the answer before someone has finished asking me a question.

Natalie:

Very much

I enjoy cooperative overlap, and it is a way to indicate my excitement!

Kendall:

Very much

I do this mostly because I will forget what I am going to say.

Differences: I do this to indicate excitement; Kendall does it because he will forget what he was going to say.

9. I am forgetful during my daily activities.

Natalie:

No, not at all

My mind just bookmarks things I need to do.

Kendall:

Very much

I am very forgetful. Out of sight, out of mind. I do it constantly. I turn my coffee on, by the time I am out of the room, it is not even remotely on my mind. Or my mom will ask me to get the mail when I take out the trash. When I get back in, she asks me if I got the mail, and I will not have; I will have forgotten the moment I walked out the door, even though it is right next to the trash. She will say ‘okay, you can get it when you go to the car,’ and I say that I have to go now, as I will forget it then, too. Whatever is going on in my head is taking up all of it.

Differences: I don’t struggle with this because my tasks are organized. Kendall is out of sight, out of mind.

10. I find it difficult to keep my attention on what I am doing, whether working or playing.

Natalie:

No, not at all

I can go off on a tangent of something that I may need more information about, but it is on topic.

Kendall:

Yes, somewhat or a little

If it is tedious and boring, yes. Otherwise, no. I can get sidetracked by the work.

Differences: Not a problem for me, but if he is not interested, Kendall’s mind can wonder.

11. I find it hard to stay sitting, even when I know I am expected to.

Natalie:

No, not at all

I like to cross and uncross my legs as they get uncomfortable.

Kendall:

Very much

It is even worse when I am expected to stay seated.

Differences: Kendall finds it close to impossible, and I have no problem at all—I have to tell myself to move, as I am often stiff from not moving for so long.

12. I find it hard to follow through on instructions or finish chores or duties, even though I understand what is expected of me.

Natalie:

No, not at all

Getting started on things that I feel anxious about is difficult. Everything else, I am pretty much a bulldozer.

Kendall:

Yes, somewhat or a little

It is hard to do it, until I start doing it. Once I get going, it is okay.

Differences: I have a hard time starting things that make me feel anxious. For Kendall, starting something is hard due to task initiation and other executive challenges.

13. I find it hard to engage in play or leisure activities that are quiet.

Natalie:

No, not at all

It is overstimulating for me to have sounds going on.

Kendall:

No, not at all

It is massively distracting to have noise.

Differences: Neither of us likes noise.

14. I don’t like having to make a sustained mental effort.

Natalie:

No, not at all

I enjoy sustained mental effort. I always have.

Kendall:

No, not at all

The phrasing of this is bad. I do it a lot. I would not say I like it, it is just a lot. I sometimes avoid things because they require sustained mental effort, because once I am in, I am in—it’s all consuming. It also depends on what it is. If it is creating a drumbeat—I like it. If it is doing my taxes, I don’t like it. It is context dependent.

Differences: This is my preference, whereas for Kendall, he can become so hyper-focused that he can make himself ill from not sleeping or eating once he gets going on something.

15. I tend to talk excessively.

Natalie:

Very much

People find that I over-talk.

Kendall:

Very much

Differences: None

16. I am easily distracted.

Natalie:

No, not at all

I get so focused on what I am doing, that everything else goes away. People used to joke that when I had a baby I would leave the baby at the store. As it turned out, my baby was my special interest, and the groceries often got left at the store.

Kendall:

Moderately

All of these are context dependent. If it is something that I am interested in, I hyper-fixate. Otherwise, my brain is going onto other things. I can be distracted by my own thoughts.

Differences: I over focus. Kendall is either hyper-fixated or distracted.

17. I have trouble waiting my turn.

Natalie:

Moderately

I can be impatient in a queue.

Kendall:

Moderately

I get impatient in situations where things do not happen immediately.

Differences: Similar

18. I often interrupt others.

Natalie:

Very much

All the time, it is a big problem.

Kendall:

Very much

I have to really make an effort not to do it, and can feel myself doing it, and tell myself stop interrupting, and keep doing it.

Differences: Big challenge for us both

Our results

Natalie:

Total score: 18

(12–42, Significant Level of Experiences Associated With Hyperactivity–Impulsivity)

Your answers indicate levels of experiences which are consistent with the hyperactivity-impulsivity component of ADHD symptoms. However, in the absence of higher levels of experiences typically associated with inattention, a diagnosis of ADHD is normally not appropriate.

And that is what I do not have, high levels of experiences of inattention.

Kendall:

Total score: 39

(24–54, Significant Level of Experiences Associated With ADHD, No Mitigating Factors)

Your answers indicate levels of experiences which are consistent with ADHD, including those associated with both inattentive and hyperactivity-impulsivity symptoms. This is not a diagnosis, and this does not necessarily mean that you have ADHD. However, generally speaking, the higher the score, the higher the number of experiences which you have reported that might, under the careful evaluation of a psychiatrist, be considered symptoms of ADHD.

Conclusion

In conclusion, it is important to consider not only a person’s traits, but why a person has that trait when assessing a person. Without these considerations, autism can be mistaken for many different conditions, such as BPD, or ADHD alone.