Autism and ADHD–Similarities and Differences

Autism Spectrum Disorder (ASD) and Attention Deficit Hyperactivity Disorder (ADHD) often have quite similar presentations, and have been found to be comorbid quite often. Some of these similarities are due to the fact that both are developmental disorders that affect the brain’s processing functions but not other aspects such as intelligence. ASD was often associated with intellectual disabilities, but has since been modified to have the specifier ‘with intellectual disability’ in these situations, presenting them as an alternate presentation rather than a ‘default.’ Similarly, ADHD was often perceived and treated as a learning disability because it was so often associated with difficulty in classrooms and typical learning environments. Both of these developmental disorders can be perceived similarly from an outside perspective, having several overlapping areas that are affected, but are very different in the actual processes that are occurring, and what areas are affected in the brain. 

One of the areas that ASD and ADHD most overlap in is sensory sensitivity because both disorders affect the way the brain processes sensory input. Many people with ADHD report similar sensitivities to those of people with ASD, including bright or flickering lights causing discomfort or pain, loud or sudden noises eliciting negative emotional reactions, quiet background noises being extremely attention-grabbing and distracting, specific textures and materials being extremely uncomfortable or very comforting and appealing, sensitivity to being too hot or too cold, and pickiness around food textures. These sensitivities can range from distracting and mildly irritating to the extremes of painful or deeply upsetting. 

Another significant similarity is in the capacity for hyperfocus, and the opposing struggle to pay attention and focus on uninteresting subjects. Both those with ADHD and ASD can experience an obsessive level of interest in specific topics, hobbies, interests, etc. This can present as constantly thinking and talking about these subjects, to the extent of not being able to dedicate significant time or focus to anything else. In ASD, these are called ‘special interests’ and can last years or longer, and are usually limited to only a few. In ADHD, these are called hyperfixations, and typically are equally if not more intense, but last a shorter duration– sometimes months, sometimes weeks or days. In these hyperfocused states, people with both ASD and ADHD will be so focused on what they’re doing it will often interfere with their ability to function in their daily lives, often missing sleep, neglecting obligations like friends, family, school, or work, and failing to take care of themselves by missing meals or other self-care activities because they are both too engaged in what they are doing and struggle to recognize the passing of time passively. 

Realistically, these are only some of the traits in which ASD and ADHD overlap. Others include impulsivity, poor emotional regulation, increased pattern regulation, and poor body awareness that can present like clumsiness or carelessness, and early in childhood indicators. Where they separate significantly, however, is the social presentations and processes. In order to have an ASD diagnosis, there must be significant social impairment. ASD is, first and foremost, a disorder that affects how the brain learns and adapts to social cues, language, and cultural and societal norms. Those with ASD have specific indicators relating to this, including things like struggling to learn or understand tone of voice, sarcasm, or metaphors. Those with ASD are often very literal and easily thrown by figurative or vague language in conversation. There is difficulty in forming friendships from a young age, and a difficulty displaying or interpreting body language. This also results in unusual presentation of emotions, and a struggle to identify one’s own emotions. The social aspect of ASD must be significant enough to impair social functioning, and is the cornerstone of the diagnosis of ASD, whereas ADHD does not have social aspects at all. 

Additionally, ASD tends to have more physical and biological indicators. Many with ASD struggle with interoception, some to the extreme that they never experience hunger, thirst, or the urge to go to the bathroom, which can have serious physical consequences. They also struggle more with identifying and exercising personal safety due to differences in perceiving pain as well as danger or fear. ASD also has a high comorbidity with physical health issues such as Hypermobility Syndrome, Ehler’s Danlos Syndrome, and Celiac or gluten intolerance, whereas ADHD does not. While both are notably hereditary, ASD is extremely unknown and inconsistent in its genetic presentation. ADHD also has not been identified as a specific set of genes, but shows much stronger and more consistent heritability, with presence within the immediate family drastically increasing the likelihood of being diagnosed. 

Both ADHD and ASD are extremely complex and multifaceted disorders due to their developmental origin. They effect many aspects of functioning and, from the outside, can appear quite similar. In reality, however, they are extremely different experiences, so much so that when comorbid they often ‘cancel out’ some aspects of each other, making diagnosis more intricate and nuanced. Much of the effects can be viewed from others, but the most significant impact is on the individual’s mind and personal experience of the world.