ADHD vs autism: how they differ and what it means when it’s both

Maybe you were diagnosed with ADHD years ago, and descriptions of autism now sound like you. Or you have neither diagnosis and recognize yourself in both. Sorting out autism vs ADHD starts with what each word means.

ADHD is a neurodevelopmental condition, meaning it is tied to how the brain develops. It involves ongoing trouble with attention, activity level, and impulse control, and symptoms usually continue into the teen years and adulthood (NIMH on ADHD). Autism is also neurodevelopmental. It involves persistent challenges with social communication, plus restricted interests and repetitive behavior (American Psychiatric Association on autism), along with differences in sensory processing (CDC autism diagnostic criteria).

Autism can be diagnosed at any age. About half of U.S. adults with a current ADHD diagnosis received it at 18 or older (CDC MMWR report on adult ADHD diagnosis (2024)), so asking these questions at 15 or 40 does not mean you missed something obvious.

Is ADHD on the autism spectrum?

ADHD is not on the autism spectrum. The current diagnostic manual, DSM-5-TR, lists autism spectrum disorder and ADHD as two separate diagnoses in the same neurodevelopmental chapter (APA summary of DSM-5 changes). Since DSM-5 came out in 2013, one person can be diagnosed with both, which the earlier manual did not allow.

Autism is called a spectrum because autistic people have a range of characteristics, needs, strengths, and challenges (NIMH on autism spectrum disorder). So “spectrum” describes the range within autism, not a scale that runs from ADHD to autism.

In everyday speech, both fall under “neurodivergent,” an informal umbrella word that is not itself a diagnosis. The conditions share some genetic risk (Mattheisen et al., Nature Genetics 2022), and they can occur in the same person (Lai et al., Lancet Psychiatry 2019).

If you were evaluated before 2013, a clinician may have given you one label even if both fit.

ADHD is not a form of autism, and neither condition is a milder version of the other. ADHD and autism are separate but related conditions. They share some genetic risk, and in adults their symptoms can overlap. One person can also have both conditions at once.

ADHD is also not high-functioning autism. “High-functioning” is an informal label some people use for autistic people who need comparatively less day-to-day support.

What sets ADHD apart from autism

The main difference between ADHD and autism is what each diagnosis is built around. ADHD centers on trouble regulating attention, activity, and impulses (NIMH on ADHD). Autism centers on social communication differences plus restricted, repetitive behaviors, a group that includes sensory differences (CDC autism diagnostic criteria). Two people can look similar on the surface, so telling ADHD and autism apart often comes down to why a behavior happens.

DSM-5 sorts ADHD symptoms into two groups, inattention and hyperactivity-impulsivity (CDC ADHD diagnostic criteria), and names three presentations: predominantly inattentive, predominantly hyperactive/impulsive, and combined (American Psychiatric Association on ADHD). Autism is described instead by how much support a person needs, from Level 1, “requires support,” to Level 3, “requires very substantial support.”

Stimming means repetitive movements, sounds, or use of objects. Rows marked “in our experience” describe what we see in clinic.

For ADHD, medications are first-line (American Psychiatric Association on ADHD), and a network meta-analysis supports medication as first-choice treatment across ages (Cortese et al., Lancet Psychiatry 2018). For autism in adults, UK guidelines advise against antipsychotics, anticonvulsants, or routine antidepressants for core features (NICE guideline on autism in adults). Support centers on skills, accommodations, and treating conditions like anxiety.

Where ADHD and autism overlap, and why they get confused

ADHD and autism can look alike, in children and in adults. NIMH notes that autism symptoms in adults can overlap with ADHD symptoms. A single behavior, such as losing track of a conversation, can have a different cause in each condition, so the clinical question is why that behavior happens.

Part of the overlap is biological. A 2022 genetic study found seven genetic locations shared by ADHD and autism, and five that set them apart (Mattheisen et al., Nature Genetics 2022).

That mix of shared and separate traits shows up in daily life, too. The two conditions often affect the same areas, like attention, social interaction, and routines, but in different ways:

Overlap is also harder to see when someone masks. Masking, or camouflaging, means using learned strategies to cover autistic differences in social settings (Cook et al., camouflaging systematic review). DSM-5 notes autism traits may be masked by learned strategies later in life (CDC autism diagnostic criteria).

People ask whether autism or ADHD is harder to live with. In our practice, that depends on the person and the support around them.

Is it autism or ADHD? How clinicians tell them apart in teens and adults

Telling autism from ADHD takes a clinician’s review of your developmental history, how your traits show up across settings and over time, and what each behavior does for you. Rating scales and structured interviews support that judgment. The answer can be ADHD, autism, both, or neither.

It’s harder to sort out in teens and adults. People who mask or rehearse conversations can seem to have neither condition during a short visit, and adults with ADHD often build workarounds, like detailed reminder systems, that hide how much effort daily tasks take. The line between the two isn’t always sharp, either. People with ADHD have substantially more autistic traits than those without ADHD, even when they don’t meet criteria for autism (Hollingdale et al., Psychological Medicine 2020). Naming those traits still helps, because they shape which supports work.

At Zellig, every autism evaluation starts with a comprehensive psychiatric evaluation, so we can also see ADHD, anxiety, or depression that may look like autism or occur alongside it. Your autism visit then uses the MIGDAS-2, a sensory-based, conversational interview that looks at sensory interests, communication, and social and emotional responses (WPS, MIGDAS-2). Because the conversation centers on what interests you, people who mask often relax, and their natural way of relating to the world comes through. You’ll finish with a feedback session and a written report that explains the results in plain language and includes recommendations for home, school, or work. We evaluate teens 12 and older and adults.

Autism with co-occurring ADHD

Having both, sometimes called AuDHD, is well documented. A 2019 meta-analysis of 96 studies estimated that about 28% of autistic people have ADHD (Lai et al., Lancet Psychiatry 2019), and a 2021 meta-analysis put the figure at 38.5% (Rong et al., 2021 meta-analysis). Among children and teens with ADHD, about 21% met the threshold for autism (Hollingdale et al., Psychological Medicine 2020).

The two sets of traits can interact. A person can feel torn between preferring routines and getting bored with sameness, or crave social contact while finding social situations hard (APA on autism and ADHD together). One condition can also make the other harder to spot: in one study of schoolchildren, only 16% of those with both had been diagnosed with both (APA on autism and ADHD together). A childhood diagnosis of one leaves the question of the other open.

The signs of ADHD and autism together in adults are the same traits from the table above, present in one person. Our AuDHD guide covers them in more depth.

Treatment is planned for both at once, and medications remain an option for ADHD in autistic people. In a controlled trial in autistic children, about half responded to stimulants, with a smaller response and more side effects than in typical ADHD (RUPP Autism Network methylphenidate trial). A Cochrane review of methylphenidate in autism found no evidence that the stimulant worsens core autism features, and it rated that evidence as low quality. Those studies were in children, so we watch side effects closely.

If you are in crisis, call or text 988, or chat with the 988 Suicide & Crisis Lifeline. It is free and confidential, 24/7. This page is general information and does not replace care from your own clinician.