If your child has been assessed for one condition and you find yourself wondering whether the other might also be present, you are asking exactly the right question. The short answer is yes: a child absolutely can have both autism and ADHD, and this combination is far more common than many parents realise.

Understanding what the overlap looks like, and why it matters for assessment and support, can help you navigate the next steps with more clarity.

How Common Is It?

Research consistently shows that autism and ADHD co-occur at high rates. Studies suggest that around 50 to 70 per cent of autistic children also meet the criteria for ADHD, and conversely, a significant proportion of children with ADHD show autistic traits. The two conditions share some neurological features, including differences in executive function, sensory processing, and emotional regulation, which is part of why they so often appear together.

Until relatively recently, clinical guidance in many countries actually prevented professionals from diagnosing both conditions at the same time. That guidance has since changed. It is now well established that the two are distinct and can and do co-exist, and that diagnosing both, where both are present, leads to better outcomes.

Why the Overlap Can Be Hard to Spot

When autism and ADHD occur together, the picture can be harder to read than when either condition presents on its own. The two share a number of surface features, and each can mask or complicate the presentation of the other.

Inattention and distraction, for example, are associated with both conditions. In ADHD, difficulty sustaining attention typically reflects a nervous system that struggles to maintain engagement without novelty or stimulation. In autism, a child may appear inattentive because their attention is focused on something of intense personal interest, or because sensory input in the environment is absorbing significant cognitive resource. Both can look similar from the outside.

Social difficulties are similarly shared but have different roots. A child with ADHD may struggle socially because of impulsivity, talking over others, or missing turn-taking cues. An autistic child may find social interaction genuinely confusing because the unspoken rules of social engagement do not come intuitively. A child with both conditions may show a combination of both patterns.

Emotional outbursts and meltdowns appear in both conditions too, though the triggers and the experience can differ. Without a thorough assessment, it can be very difficult to know what is driving what.

Why Getting Both Diagnosed Matters

It might seem like a distinction without a difference: does it really matter whether a child has one or both, if the support needs are broadly similar?

In practice, it matters considerably.

The interventions and strategies that help with ADHD do not always translate directly to autism, and vice versa. A child whose ADHD is identified but whose autism is missed may receive support that addresses some of their difficulties but leaves others unexplained and unsupported. The same applies in reverse.

Medication decisions are also affected. ADHD medication is commonly used and can be very effective, but clinicians working with a child who has both conditions need to factor in the full picture when considering whether medication is appropriate, what type, and at what dose.

School support is shaped by diagnosis too. An Education, Health and Care Plan (EHCP) or equivalent support in Ireland needs to reflect a child's actual needs accurately. A child whose autism is unrecognised may receive a support plan that addresses their ADHD but does not account for the sensory, communication, or flexibility-of-thinking needs that come with autism.

What to Look Out For as a Parent

If your child has already been diagnosed with one condition and you suspect the other may also be present, some signs worth paying attention to include:

For autism, in a child with existing ADHD: difficulty with unexpected changes to plans or routines, strong and narrow interests that dominate conversation and activity, sensory sensitivities to sound, light, texture or taste, difficulty reading social cues or navigating friendships, and a preference for predictability and sameness.

For ADHD, in a child with existing autism: difficulty sustaining attention across most activities including preferred ones, impulsive behaviour that the child seems unable to predict or prevent, significant difficulty waiting, physical restlessness or an inability to settle, and inconsistent engagement that varies day to day.

These are not diagnostic criteria, and a professional assessment is the only way to know for certain. But they are a useful guide for conversations with a clinician or your child's school.

What a Combined Assessment Involves

A combined autism and ADHD assessment evaluates both conditions within a single process rather than requiring two separate referrals and two separate waiting periods. It involves a thorough developmental and clinical history, standardised assessment tools for both conditions, observation of the child, and input from parents and school.

For families who suspect both may be present, a combined assessment is usually more efficient and provides a more integrated picture of a child's needs than two separate assessments conducted at different times.

Takeaway

Having both autism and ADHD is genuinely common in children, and identifying both, where both are present, leads to better-targeted support. If you have concerns about whether your child may have more than one condition in play, it is worth raising this directly with a clinician who has experience with both.

At Autism Services Group, we offer combined autism and ADHD assessments for children across the UK and Ireland, carried out by experienced clinicians who understand the full complexity of how these conditions can present together.