Monodiagnosis: a new term in autism, ADHD and AuDHD

This article explains what the term monodiagnosis means and why it was coined. It also covers the idea of dual diagnosis and what that means, and multiple diagnoses or multidiagnosis.

The background to autism, ADHD and AuDHD

The terms monodiagnosis and dual diagnosis refer to autism, a neurodivergent condition, and attention deficit hyperactivity disorder (ADHD), another neurodivergent condition. When someone has these conditions together, it’s known as AuDHD. This is a term used primarily by people who have AuDHD, it’s not a specific medical diagnosis.

Until recently (2013 in the US, 2019 in Europe), the official medical literature stated that you could not have both autism and ADHD together. So AuDHD is a concept that has only been recognised relatively recently, even though AuDHD people have likely been around for thousands of years.

What is a monodiagnosis?

A mono diagnosis is when you have ADHD or autism diagnosed, but you also have autism or ADHD that hasn’t been diagnosed.

So basically you’ve got both ADHD and autism, but you’ve only been diagnosed with one. The term monodiagnosis implies the existence of a second diagnosis.

“Mono” meaning “one”, from the Greek “monos” which means alone.

“Diagnosis” from Greek and Latin, meaning “to discern”.

Why was the term monodiagnosis coined?

The term “monodiagnosis” was developed because there was no specific term to describe an experience that was becoming increasingly common.

This experience is having a diagnosis of either autism or ADHD, and not realising, or being diagnosed with, the other.

As diagnosis rates for both autism and ADHD increase, there became a greater number of people who have both of these conditions but only have one diagnosis. So they know they’ve got ADHD, or know they’re autistic, without realising that there’s another condition there too. Some people don’t even realise it’s possible to have both.

Monodiagnosis can happen with both medical diagnosis and self diagnosis.

Why does monodiagnosis happen?

A few reasons.

Currently, these conditions are still assessed separately. While it’s possible to have one clinician or service diagnose both conditions in one person, it’s still a separate process. The conditions are still seen as independent, despite lived experience describing huge overlaps, and the increasing numbers of people with a dual diagnosis.

There are still a great many people, both in the medical field and outside, who don’t realise that it’s possible to be both autistic and have ADHD. The traits of these conditions seem to conflict which is why some people believe it’s impossible to have both.

It’s often the case that one condition will overshadow the other. For example, a person’s ADHD might affect their life to such an extent that it’s all they focus on and all a clinician will see. The autism is present in the background but isn’t causing the issues that might compel someone to seek help. Or the reverse could be true, a person’s autism might present so obviously that they get that diagnosis, and the ADHD is missed.

Who coined the term monodiagnosis?

The term monodiagnosis was coined by me, Rachel Morgan-Trimmer. As well as being a neurodiversity consultant, I’m autistic and have ADHD so I know first-hand the challenges of both a mono and dual diagnosis.

I identified with ADHD when I was 23, and with autism in my late 30s or early 40s. I was diagnosed with autism at the age of 46 and with ADHD at 48.

In my work, I speak to huge numbers of neurodivergent people, and one recurring theme was that of having one diagnosis but suspecting another. That’s why I coined the term “monodiagnosis”. I hope it will encourage an understanding of this shared experience, and be a way that people learn about themselves.

What’s a dual diagnosis?

A dual diagnosis, in this context, means you have both ADHD and autism.

Sometimes we call that AuDHD. This is a term used primarily by people who have AuDHD, though of course anyone can use it. It’s still a fairly new term so not always widely understsood.

The majority of people with AuDHD get one diagnosis and then another. Some might get them diagnosed back-to-back, others might have years between their diagnoses.

In neurodiversity, we use the term “dual diagnosis” to refer mainly to autism and ADHD. But the term “dual diagnosis” is also used in other contexts. So if you’re using it to refer to autism and ADHD (or AuDHD), you might choose to be clear about what you’re referring to.

The term “dual diagnosis” is most commonly used to refer to a mental health condition co-occuring with substance misuse.

What’s a multiple diagnosis or multidiagnosis?

Multiple diagnoses can be used to refer to two or more of any medical condition (including neurodivergent conditions, mental health and physical conditions). It’s often used to refer to a combination of mental health conditions.

Co-existing or comorbidity can also describe a person having more than one neurodivergent, mental health or physical condition.

The term “multidiagnosis” is not widely used, so I’m proposing it to be adopted by the neurodivergent community. It could describe any neurodivergent condition (including dyslexia, dyspraxia and dyscalculia) which co-occurs with any other.

Or it could describe any neurodivergent condition which co-occurs with a mental health disorder. This represents the majority of people with ADHD, autism or both.

It could describe neurodivergent people who also have a physical health condition. Again, this is common, particularly with autistic people.

Or it could be any combination of the above.

Why is monodiagnosis, dual diagnosis and multidiagnosis important?

I believe it’s important for people to have the language to accurately describe their experiences and identity.

A monodiagnosis isn’t just a word, it’s a way of explaining how you have (or had) one diagnosis but should have (or have had) two. It can help you connect with others who have similar experiences and help you make sense of yourself.

The terms “dual diagnosis” and “multiple diagnoses” or “multidiagnosis” serve the same purpose. To help accurately describe and communicate your experiences and identity.

I believe that’s something that everyone deserves.