ADHD or Autism in Adults?

Many adults who wonder about ADHD also wonder about autism, and the reverse. Both are neurodevelopmental conditions that start in childhood, both can make work and relationships harder, and both can involve trouble with attention, restlessness and sleep. They are still different conditions, and a person can have one, the other or both. This page compares them and explains why telling them apart in adults takes care.

Why they get confused

The National Institute of Mental Health (NIMH) says plainly that diagnosing autism in adults is often more difficult than in children, and that in adults some autism symptoms can overlap with those of anxiety disorders or ADHD. A few overlaps explain most of the confusion:

• Social difficulty. Adults with ADHD may interrupt or talk a lot, which NIMH lists among adult ADHD symptoms. Autistic adults may have difficulty with the back and forth of conversation or with reading another person's point of view. From the outside, both can look like "not good with people".
• Attention. ADHD involves distractibility. Autism can involve intense, lasting interests that make it hard to shift attention elsewhere. Both can look like "not paying attention" to the thing in front of you.
• Restlessness. ADHD restlessness and the repetitive movements seen in some autistic people can both read as fidgeting.
• Sleep and irritability. NIMH notes sleep problems and irritability in autism, and sleep problems in up to 70% of adults with ADHD.

Side by side

The rows come from NIMH's publications on autism and on adult ADHD. A 2022 review in Frontiers in Psychiatry adds a description from clinical experience with children: children with ADHD tend to be boisterous, talkative and eager rather than apprehensive about interacting, while autistic children are more often distinguished by communication difficulty, repetitive behavior and a preference for the predictable. That description is of children. In adults the picture is less clear-cut, which is NIMH's point about adult diagnosis being harder.

When both are present

Older diagnostic rules did not allow both diagnoses at once. The 2022 review notes that the previous edition of the DSM made ADHD and autism mutually exclusive, while the current edition (DSM-5) describes each condition in the other's text and admits that they can co-occur. NICE, the UK's National Institute for Health and Care Excellence, goes further in its ADHD guideline: it recommends against excluding an ADHD diagnosis because of a pervasive developmental disorder such as autism.

How often they co-occur depends on how it is measured:

• A 2019 meta-analysis in The Lancet Psychiatry, pooling 96 studies, estimated that 28% of autistic people also have ADHD. Rates were higher in clinical samples than in population and registry studies.
• The 2022 review notes that figures of 50% to 70% are often quoted, and questions whether some attention problems in autistic people are part of autism itself rather than separate ADHD.

The honest summary is that co-occurrence is common and the exact rate is uncertain. "AuDHD" is an informal term some people use for having both. It is not a diagnosis, and it does not change how each condition is assessed. The guide page on ADHD and autism together covers what living with both can involve, and the site's article on AuDHD in adults discusses the term.

Why the distinction matters

• Supports differ. NIMH describes autism supports as behavioral, psychological, educational, occupational and speech-language services, and help with social skills, life skills and job training. NIMH describes the most common adult ADHD treatments as medication, usually stimulants, and psychotherapy.
• Medication decisions. NICE recommends offering people with ADHD and autism the same ADHD medication choices as other people with ADHD. The 2022 review notes that amphetamine-based treatment can have paradoxical or unwanted effects in some autistic people, which is one reason a prescriber wants the full picture before starting.
• Self-understanding. NIMH notes that a correct autism diagnosis in adulthood can help people understand past challenges and identify their strengths. The same is true of an accurate ADHD diagnosis, and of learning that neither fits.

Who evaluates autism in adults

NIMH advises adults who wonder whether they are on the autism spectrum to ask a health care provider for a referral for an autism evaluation. Adults can be referred to a neuropsychologist, psychologist or psychiatrist who has experience with autism. That evaluation asks about social communication, sensory issues, repetitive behaviors and restricted interests, and often includes family members who can describe early development.

Dr. Shershow's evaluation is an adult ADHD evaluation. It looks at current symptoms, childhood, school and work history, health, and other explanations for the symptoms, and it ends with what was found and the treatment options that fit. It is not an autism assessment. If autism is a real question for you, it is reasonable to raise it and to seek a separate autism evaluation as NIMH describes. The guide on clinical evaluation versus neuropsychological testing explains how the different kinds of assessment fit together.

Questions that help sort it out

• As a child, was your main difficulty sitting still and staying on task, or understanding and joining in with other children?
• Do changes in plans feel mildly annoying, or genuinely distressing?
• Are sounds, lights, textures or crowds harder for you than for most people?
• When you lose focus, is it because something else grabbed your attention, or because the task is not your area of interest?
• Can a parent or older relative describe your first few years, including speech and play?

Answers to these are not a diagnosis. They are the kind of history an evaluator will want, alongside the formal criteria explained in the adult ADHD diagnostic criteria. If you were diagnosed with one condition years ago and now doubt it, when to get a second opinion may help.

When to talk to a clinician

If attention, social strain, sensory overload or difficulty with change has been affecting your work, relationships or daily life, these can be signs worth discussing with a clinician. You do not have to decide in advance which label fits. The adult ADHD self-test screens for ADHD symptoms only; it does not screen for autism and does not diagnose either condition. To see how an adult ADHD evaluation works, read about adult ADHD testing in NYC or adult ADHD testing in New Jersey.