Dealing with a mental health condition or diagnosis can be confusing on its own, and comorbid diagnoses can make it all the more difficult to understand and seek the appropriate treatment. 

Here, we’re taking a closer look at what it means to have comorbid diagnoses, the overlap between autism and ADHD (sometimes called AuDHD), the features of each condition and where they might intersect, and where to start when it comes to seeking treatment for a combination of autism and ADHD.

At Augmentive, we aim to provide holistic, tailored mental health support to everyone so they can live their life to the fullest, so if you have questions about autism, ADHD, or the occurrence of both conditions at the same time, we can help. 

What is autism?  

Autism is a neurodevelopmental condition that affects how people interact with others, the world around them, and how they understand and respond to sensory information. People with autism may experience common sensory issues which can lead to negative reactions to certain triggers. They may experience difficulties with social communication and interaction, restricted or repetitive behaviours or interests, or may have different ways of learning, moving or paying attention. 

It is important to remember that each person with autism will have their own unique symptoms and traits that are different to someone else with a similar diagnosis. There is a wide scope of symptoms which are thought of as a spectrum, so everyone will require differing levels of support. 

Some of the main symptoms of autism that adults experience may include (but are not limited to): 

• Trouble reading social cues, participating in conversations, and relating to the thoughts and feelings of others 
• Difficulty building and maintaining friendships 
• An inability to read body language or facial expressions 
• The use of a robotic or monotone speaking pattern that does not convey true emotions 
• Avoidance of eye contact during conversations
• Restrictive and repetitive behaviours used often 
• Trouble regulating emotions 
• Difficulty with changes to routine, especially if they are last-minute
• Fixation on one or two favourite subjects that the individual cares deeply about or is extremely skilled in 
• Sensitivity to sensory input such as pain, sound or touch – according to the Autism Research Institute, an autistic person experiencing sensory issues may withdraw from physical touch, refuse to wear certain types of clothing, and more

What is ADHD?

ADHD stands for attention-deficit/hyperactivity disorder, which is a type of neurodivergence. This means the brain is hard-wired differently to neurotypical individuals.

In adults, symptoms of ADHD might include (but are not limited to) things like having trouble focusing, impulsive behaviours, and finding it difficult to pay attention. Many of these symptoms can make everyday life challenging for those with ADHD, as they affect things like their learning, studying, working, organising, managing time, or getting tasks done. ADHD tends to present differently in women than in men, so women might show less features of hyperactivity and more of inattentiveness.

Signs of ADHD include things like:

• Regularly making what appear to be careless mistakes
• Trouble paying close attention to details and maintaining attention during long tasks
• Trouble organising tasks and activities, and managing time
• Frequently losing important items like keys or phones
• Forgetting things like paying household bills or attending appointments
• Difficulty waiting, such as in a line or for their turn to speak
• Restlessness, difficulty sitting still, fidgeting or squirming a lot
• Excessive talking, interrupting, or answering questions before they are finished
• Being easily distracted by unrelated thoughts or external stimuli 

How do ADHD and autism overlap? 

In years gone by, the medical community was doubtful about diagnosing someone with both ADHD and autism, and as a result there have been very few studies looking at how and why these two conditions might overlap. 

Current research still indicates that ADHD and autism are two distinct conditions and separate diagnoses rather than one neurotype existing on the same spectrum. While there appears to be no question that autism and ADHD can exist together, there continues to be debate as to how commonly this comorbidity occurs. 

Regardless, the overlap in symptoms can make it difficult to ascertain which condition is present, or whether both exist together, which makes diagnosis challenging. 

In recent years this comorbidity has come to be known as AuDHD, autiHD, and other name combinations in an effort to characterise it, but to date there is no official name for the combined autism and ADHD diagnosis.

"Some of the symptoms of Autism may buffer or mask the symptoms of ADHD whilst some symptoms overlap. With Autism a person can find change difficult and they can like systems and structure but having ADHD can make putting systems in place difficult. The Autism might push a person in managing their anxiety around change and lack of structure to put a lot of systems in place that they rigidly live by so that might mask that element of ADHD where they find routine and systems easy."
- Dr Chetna Kang, Consultant Psychiatrist

Who is likely to experience both ADHD and autism?

With a lack of research on the comorbidity of ADHD and autism, no definitive links have been discovered that would indicate why certain individuals develop both conditions and others do not. One study has identified a rare gene that could be linked to both ADHD and autism, which could explain the comorbidity, however it is clear that much more research is required to understand this potential connection. 

It is worth noting that another study looking at the three diagnostic groups of autism-only, ADHD-only, and autism with ADHD, found that males experienced higher odds of all three diagnostic categories than females. 

What symptoms are the same?

Autism and combined type ADHD are entirely different, however the overlap lies in some of their core symptoms being the same. Here are some of the areas in which the two conditions are thought to overlap: 

• Physical movement: Although not everyone with ADHD and autism will experience this, both share the symptom of atypical physical movements such as fidgeting or stimming behaviours. 
• Impulsivity: Symptoms of ADHD impulsivity might include things like speaking out of turn or jumping up at inappropriate times, which can overlap with autism symptoms like an inability to read social cues. 
• Attention: Studies have shown that ratings of attention deficit were no different between children with autism of any severity and children with combined type ADHD, so if this is a primary symptom it can be difficult to know which condition the symptom belongs to. 

While attention is much more associated with ADHD symptoms, studies have found that selective attention is significantly more common among children with autism of any severity than in those with ADHD (inattentive or combined type ADHD). 

Those with ADHD may struggle to focus their attention on a specific task, but can achieve hyperfocus when the activity interests them, in a similar way to those with autism who can appear to obsess over things they enjoy and excel in certain subjects as a result. 

• Social difficulties: Both those with autism and with ADHD can face challenges when it comes to social interaction and making friends. For those with ADHD this can be due to their tendency to talk continuously, interrupt others, and be unaware of how their words may have affected someone else. 

Communication challenges are also a feature of autism, as people with this condition may struggle by fixating on one topic, or not initiating social interactions. 

Both ADHD and autism have also been linked to atypical processing of faces, which can add to the difficulties they face in social situations. 

• Executive function issues: Problems with executive function may include things like difficulties organising one’s time, achieving tasks, and finishing projects. Both those with autism and ADHD can struggle in this area. 
• Emotional dysregulation: Emotion regulation can be difficult for those with ADHD and for those with autism, and although the underlying reasons for why might be different, on the surface this may look the same which can cause confusion when diagnosing. 

What does it mean to have a comorbid diagnosis? 

Comorbidity means an individual has more than one illness or condition at the same time. This can be either completely coincidental, or one condition could directly cause the other. 

In the case of autism and ADHD, the research indicates that those with ADHD have a much higher chance of being diagnosed with autism at some point in their life compared to someone who does not have ADHD. 

If you have been diagnosed with ADHD it is important to understand the existence of this comorbidity so you can be aware of symptom overlaps and recognise potential autism. Doing so can help you better understand the complexities of your condition(s) and get the support you need if you do have both. 

How common is it to have both autism and ADHD?

The lack of studies on the comorbidity of autism and ADHD means it is difficult to know exactly how frequently this occurs. According to some studies, 50-70% of those with autism also present with ADHD, and the Centers for Disease Control and Prevention (CDC) estimates that 14% of children with ADHD also have autism. 

As mentioned, there are still questions as to how frequently this comorbidity exists, so some studies have also explored the idea that the attentional impairment and physical restlessness in those with autism may in fact be a characteristic of their autism rather than a feature of comorbid ADHD. 

What makes a comorbid diagnosis more challenging to diagnose and treat? 

Diagnosing comorbid autism and ADHD is difficult from the outset because children with autism can be identified prior to turning 3 years old, whereas children with ADHD are often diagnosed later in life. 

Many doctors lack the specialised training to understand the unique combination of autism and ADHD symptoms, and how they can manifest differently in each individual, so it is easy for GPs and other general medical practitioners to miss early signs and misdiagnose or under-diagnose their patients. 

Research suggests that in clinical practice, psychiatric clinicians often under-recognise comorbidity in mental health, so when a person is diagnosed with one condition, the signs and symptoms of any comorbid diagnoses may be missed.

It is also extremely hard to treat a comorbidity of ADHD and autism because some of the symptoms may appear to contradict each other. For example, someone with autism may prefer a very rigid routine, whereas someone with ADHD may have issues with organisation and sticking to a routine. When one symptom essentially ‘cancels out’ the other, a secondary condition can be easily missed. 

Unfortunately there is still stigma attached to the conditions of autism and ADHD individually, so those with both conditions may experience more of this stigma, causing barriers to their diagnosis and treatment. 

"Autism is actually diagnosed as Autistic Spectrum Disorder because it is a spectrum of symptoms. You have a milder end to a more severe end, with the milder end being less easy to pick up. The degrees you have it plays into the ADHD. With ADHD it is not so much of a spectrum, you either have it or you don’t, but what might vary is the type of ADHD you have, whether you present inattentiveness, hyperactivity, impulsivity or a combined type. That interplay is going to have an impact on the AuDHD."
- Dr Chetna Kang, Consultant Psychiatrist

Why is the correct diagnosis so important?

Due to the high number of ADHD symptoms seen in children with autism, many are initially misdiagnosed with ADHD. This can lead to receiving the wrong care or even the wrong medication, which can cause a number of issues. For example, if an individual is prescribed stimulants for ADHD when this is not the cause of their symptoms, not only do they lack the proper diagnosis for their condition but their symptoms could also worsen as a result.

Misdiagnosis can be dangerous for those with comorbid ADHD and autism, as they may experience worse symptoms. Research has suggested that in some studies children with both conditions experienced more debilitating symptoms than children who did not have autism symptoms, so the importance of addressing the symptoms of the relevant condition cannot be overstated. By achieving the correct diagnosis, those with both autism and ADHD can receive the attention and support they need. 

“Prior to my ADHD diagnosis, I had tried to implement many of the things that my research told me would support my autistic brain. Though I had made a lot of progress, some things just didn’t work, and my subsequent ADHD diagnosis made sense of that for me.” – Ella Tabb via Autism.org

How do I know if I have both autism and ADHD? 

It is important to discuss your symptoms of ADHD or autism with a specialist who has experience working with both conditions. While everyone’s combination of symptoms of ADHD or autism will be unique, here are some of the most common overlapping symptoms that you may be able to notice in yourself or a loved one: 

• Sensory issues – these can occur in those with autism, while sensory overwhelm can affect those with ADHD 
• Hyperfixation – this is a symptom of both conditions 
• Interrupting people before they have finished speaking – this is a trait of both ADHD and autism, though they have different underlying reasons for doing so 
• Insomnia and sleep problems – these can affect those with ADHD and autism 
• Restlessness – hyperactivity and fidgeting can affect those with both conditions 
• Stimming – this is thought of as an autism-related behaviour, but it can also occur as an ADHD symptom
• Building and maintaining friendships – this can be difficult for those with autism and ADHD
• Executive function struggles – these are common for those with autism and those with ADHD 
• Emotional dysregulation – this can be a problem for both those with autism and those with ADHD 
• Depression and anxiety – these mental health concerns can be an issue for those with ADHD just as they can be for those with autism 

How do I seek treatment and support for this? 

If you recognise some of the typical overlapping symptoms in yourself or a loved one, the best place to start is to speak to a professional who is a specialist in both ADHD and autism conditions so that you can get help recognising where your symptoms may be overlapping, and whether or not a comorbidity exists. 

If you are already working with either an ADHD specialist or an autism specialist, you can reach out to them for their advice on potential comorbidity, as they may be able to help or point you in the direction of someone with the specialisms you need. 

You can find out more about the support available and what is involved in a private ADHD assessment here, or you can learn more about what to expect from an adult autism assessment here. 

ADHD and autism are both lifelong conditions that can be managed with support, and it is important to receive the correct diagnosis and support for you so you can move forward with treatment that addresses your most challenging symptoms.

At Augmentive, we believe advice and support for those with ADHD and autism should always be bespoke and tailored to the individual to help with their specific symptoms. Our free 15 minute consultation can help you find the relevant therapist who specialises in both conditions and can assist you in treating and managing your ADHD and autism in daily life. 

Whether you’re feeling off-kilter or want to shake up your routine, our state-of-the-art mental wellbeing platform gives you quick and seamless access to world-class support on your terms, from a private adult autism assessment or ADHD diagnosis, to helping you find a psychiatrist near you for support on your journey.

DISCLAIMER: The content published by Augmentive is not designed to treat, diagnose, cure, or prevent any disease or condition. Always consult your GP or a qualified healthcare provider with any questions regarding a medical condition and before starting any therapy, diet, exercise, or any other health-related programme.