ADHD and autism together

Half an explanation

For a long time, ADHD and autism were treated as separate and largely unrelated conditions. In adults, the reality is very different. The two frequently occur together, and one of the most common patterns in neurodevelopmental assessment is the person who has been assessed for one and never considered for the other. They leave with half an explanation, and often with the sense that something still does not add up.

This guide looks at why the two conditions so often co-occur, why the overlap is missed, and what it takes to assess both properly. For the clinical detail of each assessment on its own, see the ADHD assessment and autism assessment pages; where both are in question, the combined ADHD and autism assessment page describes how they are considered together.

Both are neurodevelopmental conditions

ADHD and autism are both neurodevelopmental conditions, meaning they are part of how a person’s brain has developed from early life rather than something acquired later. Because they share this developmental origin, it is unsurprising that they often travel together. A substantial proportion of autistic adults also meet criteria for ADHD, and a substantial proportion of adults with ADHD are also autistic. For years the two were rarely diagnosed in the same person, in part because older diagnostic conventions discouraged it. That has changed, and current practice recognises that the two commonly coexist.

Why the overlap is so often missed

The main reason is simple. If someone is referred and assessed for one condition, the other may never be looked for. An assessment framed around ADHD alone will tend to find ADHD, and an assessment framed around autism alone will tend to find autism, and neither will necessarily ask the questions that would reveal the other. In Dr Crocker’s experience, this is one of the most frequent gaps in adults who arrive already carrying a partial diagnosis.

Masking makes the picture harder still. Many adults who reached adulthood undiagnosed have spent years developing strategies to hide their difficulties, and those strategies can obscure both conditions at once. The effort involved is considerable, and it tends to break down at points of increased demand, which is often when people finally seek assessment. Masking runs through the stories of ADHD in women and late autism diagnosis alike, and it is one of the reasons the assessor’s experience matters so much.

How they can look similar, and how they differ

Part of the difficulty is that ADHD and autism can produce similar surface features for very different reasons. Difficulty with focus, feeling overwhelmed, social exhaustion and problems with organisation can all appear in either condition. Yet the underlying drivers differ. Where ADHD tends to involve difficulty regulating attention and a need for stimulation and change, autism tends to involve a preference for predictability and routine and a different way of processing social and sensory information.

Why it matters to assess for both

A diagnosis that captures only part of the picture leads to support that only partly fits. Treatment for ADHD, including medication where appropriate, can be very effective, but it does not address the autistic features of someone who is also autistic. Equally, understanding and adjustments built around autism will not resolve the attention and impulsivity difficulties of co-occurring ADHD. When both are recognised, the explanation finally fits the person’s whole experience, and the support offered can be shaped accordingly.

Co-occurring anxiety and low mood are common alongside both conditions, and they are frequently what brings someone to services in the first place. When the neurodevelopmental picture beneath them is missed, treatment aimed only at mood or anxiety often produces an incomplete response.

What a combined assessment involves

A thorough assessment does not decide in advance which condition it is looking for. Rather than running a single diagnostic script, it examines the whole history: what is difficult now and in which settings, what those difficulties cost, and whether the traits reach back into early development even if nobody named them at the time. Anxiety, depression and other possible explanations are weighed rather than set aside, and the recollections of someone who has known the person a long time — a parent, sibling or long-standing partner — are included wherever possible. Experience counts here too: well-masked adult presentations of either condition are easy to miss without it.

At Caledonian Psychiatry, the combined ADHD and autism assessment runs over three 60-minute appointments by secure video. It follows NICE guidance and Royal College of Psychiatrists standards, with the ADHD component aligned with the AQAS (ADHD Quality Assured Service) standard; the published quality standards for ADHD and autism assessment explain what those benchmarks mean in practice. The free screening questionnaires cover both conditions and can help you decide whether a full assessment is worth pursuing, though a screening score — high or low — is never an answer on its own.

Getting an assessment with Caledonian Psychiatry

Caledonian Psychiatry is regulated by Healthcare Improvement Scotland as an independent medical agency (reg. no. 03427) and delivers assessments to adults across Scotland by secure video. Every assessment is conducted personally by Dr Crocker, a psychiatrist (MRCPsych) whose day-to-day clinical work is adult ADHD, autism and mental health — you can read more about our approach and the clinical team.

You do not need a GP referral: most patients refer themselves directly, using the contact form below or by emailing or calling the practice. It helps to have a copy of your GP summary records and, ideally, a short GP letter — neither is required in order to be assessed, but they make everything smoother and support safe prescribing if medication becomes part of the plan. The combined assessment costs £1,300 across the three sessions, £300 less than booking the £800 ADHD and £800 autism assessments separately; the fees page sets out the full schedule.