Attention Deficit Hyperactivity Disorder (ADHD) And Autism: Differences And Similarities

ADHD and autism share some similarities — to the point that, if you're Googling symptoms, you can easily get results matching both without really having any idea what diagnostic beast you're dealing with. They are ultimately different disorders, however, and autistic people and those with ADHD will often have very different needs. 

What do you need to know?

What is ADHD? What is autism?

Attention-deficit/hyperactivity disorder, or ADHD, is the most common neurodevelopmental condition in children — just under 10 percent of all kids are estimated to be affected. It's characterized by a pattern of inattentive or hyperactive and impulsive behavior, or (most commonly) a combination of the two. 

• The inattentive part of ADHD can manifest as trouble paying attention to small details, staying on task (those affected find it hard to finish what they started), and remaining focused on conversations for longer periods of time. They easily forget responsibilities or items and may be described as a bit of a "scatterbrain". 
• The impulsive and hyperactive aspects of ADHD mean a person is "always on the go". They need to be doing something with their bodies and are often seen fidgeting, or, if they're children, getting up to run around. They may talk a lot and find it hard to wait their turn. They may be impulsive, wanting to start something they get in their head immediately, for instance. 
• It's possible for a person with ADHD to have mostly inattentive or mostly hyperactive and impulsive symptoms, but often, this diagnosis combines elements of both. 

Autism spectrum disorder is another neurodevelopmental condition. One in every 59 children are believed to be autistic. Autism, too, is characterized by two main areas of difficulty:

• Difficulties with social communication and interaction. These may manifest as difficulties initiating conversations or participating in them, a reduced ability to share thoughts and emotions, trouble understanding how social relationships "work" among people who are not autistic, and thus finding it hard to maintain these relationships. Differences in non-verbal communication are another aspect of this. Autistic people may, for instance, have trouble maintaining eye contact, display unusual body language, and speak loudly or in a monotonous voice. 
• A pattern of behavior centered around a preference for sameness and routines and distress when faced with change. This can include an insistence on doing the same things in the same way, meltdowns when changes occur, and very strong and particular interests (sometimes called "special interests" or "autistic obsessions". It also includes what's known as "stereotyped movements", more often referred to as stimming in the autistic community. Motor movements such as hand-flapping and rubbing a blanket or chewing on an object are common, but something like repeating a mantra is another form of stimming. 

What are the similarities between autism and ADHD? 

There are quite a few, actually, and they'd include:

• Both ADHD and autism are neurodevelopmental conditions, meaning they are characterized by differences in brain development and functioning. 
• Both have strong genetic components, which means they often "run in families". 
• Both are more likely to be diagnosed in boys than in girls — which may be because they're truly more prevalent in males, or because females manifest with slightly different symptoms that are more likely to remain unrecognized. 
• Both are frequently misunderstood — as in, though many people will have heard of both autism and ADHD by now, they may not have clear idea of what these conditions are and how they manifest, or even believe they're "real disorders".
• Another important thing to consider is that both conditions exist in adults as well as children (autistic children and kids with ADHD grow into autistic adults or adults with ADHD), though the symptoms may evolve over time.

Symptom-wise, there is also some overlap between ADHD and autism:

• Autism and ADHD may both lead to unusual motor movements. In the case of ADHD, these stem from hyperactivity, however, while autistic people use these "stereotyped" movements to cope with stress and other strong emotions. 
• Autism and ADHD can both lead to unusual behaviors in social settings, as well, such as finding it hard to engage in "normal" conversation or blurting out answers at times that are considered inappropriate. In the case of ADHD, inattention or impulsivity is the cause. Autistic people may, meanwhile, not understand the social rules of neurotypical communication. 
• Autistic people and people with ADHD can both show tantrum-like behavior. Autistic people may have meltdowns when they struggle with change or are overloaded with sensory stimuli, while those with ADHD may be hyperactive and bored. Combined with reduced impulse control, this can lead to something that resembles a tantrum.
• Autism and ADHD can both lead to difficulties with executive functioning — skills that involve planning and completing tasks. Autistic people are more likely to struggle with planning and improvising, however, while those with ADHD may find it hard to control their impulses.

What are the differences between ADHD and autism?

Though there are many symptomatic similarities between these two conditions, where they occur, they do so for different reasons. This is because autism and ADHD are ultimately very different clinical entities at heart. 

Autism often features speech delays, something not associated with ADHD, and the well-known autistic hyperfocus on a particular subject for prolonged periods of time isn't something you'd typically see in ADHD, either. 

A comprehensive evaluation will allow a diagnosing medical professional to differentiate between the two. This is important, because treatment for the two conditions is also very different — people with ADHD are often prescribed stimulants such as Ritalin to help them improve their ability to focus, but someone on the autism spectrum may react to such medications in very unexpected ways. Behavioral therapies can, on the other hand, help both autistic people and those with ADHD, but therapeutic programs are designed differently.

Is it possible to have both ADHD and autism?

Yes, it is. The CDC estimates that around 14 percent of people with ADHD are also autistic. This overlap may be explained by the fact that some of the same genes have been implicated in the development of both these disorders. The previous diagnostic manual made a dual diagnosis impossible, but a clearer understanding of the fact that they can be comorbid means that both conditions can now be diagnosed in the same person.

Due to the fact that ADHD and autism share some possible symptoms and ADHD is much more commonly diagnosed, even by family doctors and pediatricians, it's not impossible for an autistic child to initially be misdiagnosed as having ADHD if they do not display obvious language delays. 

The only way to determine whether a person is autistic, has ADHD, or possibly both is for them to attend a comprehensive diagnostic evaluation.