04/03/2025
The Importance of Thorough Differential Diagnosis in ADHD and Autism
My electronic copy of the DSM-5-TR is 1377 pages, containing hundreds of diagnoses and their subtypes. It is not the layperson’s job to know the difference between them, but as a provider who performs many different types of evaluations, it is mine.
Over the last few years, there has been a profound public interest in neurodivergent disorders, with good reason. Many of these disorders have traditionally gone underdiagnosed. People are struggling and want and deserve answers.
There is information all over the internet and social media regarding the signs and symptoms of both ADHD and Autism. Unfortunately, as suggested by a recent study, a disturbingly high percentage of the information that is out there is misleading or wrong. There is little differentiation between what is a clinical level symptom, and what is normal. There are individuals on social media who talk about the symptoms of both disorders; however, the symptoms that they are describing, while frequently occurring in ADHD or Autism, also occur equally in other types of disorders, and are not, in fact, diagnostic criteria for either disorder. There is also frequently confusion between a “symptom” and a disorder.
For instance, in the case of ADHD, both individuals and many providers frequently confuse inattention, which is the general symptom, with the specific disorder of ADHD. But there are many different causes of inattention, only one of which actually represents ADHD. Recently, I had an adult woman in her 40’s, who had never had symptoms of inattention prior to a recent brain injury ,referred for evaluation for ADHD, because both of her rehabilitation therapists had told her that what she was experiencing, “sounded a lot like ADHD.” However, they were confusing problems with inattention (the symptom) with ADHD (a disorder). In fact, one of the most common symptoms following TBI is inattention, which is a symptom of the brain injury, and not of ADHD. And it is important to know the difference in order to receive the best treatment .
Back when presenting cases were not as complex, I used to do more “Yes” or “No” types of ADHD and Autism evaluations. However, over the last several years, it has become clear to me that what most individuals are seeking is accurate differential evaluation for their clinical symptoms so that they can find relief. They are frequently presenting with a concern of ADHD or Autism, because they know that they have an issue; but may not be aware of all of the possibilities that their symptoms could encompass, and some of the information that they have been able to seek out has been incomplete, or limiting of possibilities. Certainly, many people coming to my office DO have ADHD and Autism, but, just as frequently, they have a different problem, and stating, “No, you don’t have….” without being able to give them alternative explanations doesn’t fully address their concerns And, inevitably, their next question becomes, “Well then, what is it?”
While ADHD, does encompass symptoms such as distraction, procrastination, difficulty with organization, and executive functioning problems, these symptoms are not just indicative of ADHD, and many occur just as frequently with certain mood issues, anxiety, learning or more general cognitive problems, processing speed issues, TBI, medications, history of extensive alcohol/drug use, certain medical conditions, other types of executive dysfunction, and so much more. Similarly, Autism is frequently thought of as an issue of social awkwardness and/or discomfort, although these represent only a piece of the diagnostic criteria for this disorder, and other disorders of social functioning, mood issues and/or trauma, personality styles, language disorder problems, etc. can all overlap. Similarly, OCD or OCPD types of behaviors can also be mistaken for the restricted and/or repetitive behaviors of Autism Spectrum Disorder.
The differential diagnoses between these disorders can be complicated. And, because the majority of self-report measures for ADHD and Autism are designed to screen for only a single disorder, without mapping symptoms to any other diagnostic possibilities, nearly everyone who is having symptoms will score very high on them, even though the symptoms may come from a completely different place. For instance, individuals with TBI score very high on most self-report measures for ADHD, even though that is not the most appropriate diagnosis for them.
For these reasons, if the goal is to go past providing a label, and to help determine the underlying causes of why an individual is struggling so that they may seek appropriate treatment, I frequently don’t feel comfortable just administering a self-report measure and doing a good clinical interview. While that is absolutely appropriate to rule out ADHD and/or Autism in cases where history, symptoms, and clinical presentation do not align, it is typically not adequate to answer the, “Well, then what is it?” question. This is especially true given that I am not the regularly treating provider for these individuals, so my time interacting with them and learning about them is limited. The ability to gather more data can be crucial.
If clinical interview is not enough, well-validated instruments capable of looking at multiple psychological constructs at once are frequently helpful, in conjunction with briefer testing of attention and cognition. And if those results are ambiguous, more complete neuropsychological evaluation can help to determine if attentional issues may be coming from a different cognitive or learning problem.
If someone has a genuine memory problem rather than an attentional one, if their anxiety or other psychological symptoms are interfering with their executive functioning, if there are possible medication or disease effects, if autoimmune problems are showing up in cognitive testing, or if alcohol use may be putting someone at risk for an acquired attentional problem, then I want to try to not mislabel that as ADHD if I can avoid it, perhaps masking a different issue. Similarly, if social problems or restricted behaviors are coming from a place other than Autism, I want to be able to direct someone to the most appropriate types of treatment.
It is not the responsibility of the person walking through my door to be aware of all of the diagnostic possibilities that could be causing their symptoms. But, to the best of my ability, as I am the one charged with the request of evaluating them, it is mine.
