Can ADHD and Autism overlap?

adhd vs autism

Until around 10 years ago, ADHD and autism were two conditions thought to be mutually exclusive, one not being able to exist at the same time as the other. However, in 2013, The American Psychiatric Association (APA) wrote DSM-5, The Diagnostic and Statistical Manual of Mental Disorders, a reference book on mental health and brain-related conditions and disorders and it was found that, through a dual diagnosis, autism and ADHD often coincide.

An estimated 30-80% of children with autism also meet the criteria for ADHD and conversely, 20-50% of children with ADHD for autism. Professor Jan Buitelaar of child and adolescent psychiatry at Radboud University in Nijmegen, Netherlands, has the view that “ADHD can occur without signs of autism, but autism always occurs with features of ADHD or other conditions.” Along with her team, she also has proposed that autism and ADHD are different manifestations of a single condition with a range of subtypes, each having a distinct time of onset, mix of traits and progression.

There are many differing views on the overlap between ADHD and autism, and with both conditions possessing many of the same traits, it is a difficult link to make.

ADHD and Autism: What are the similarities and differences?

ADHD is a very common neurodevelopmental disorder that usually appears during childhood. There are 3 subtypes of ADHD: the first being hyperactivity and impulsivity, affecting a person’s behaviour and control of physical movements. The second is inattentiveness, which affects a person’s ability to concentrate and sustain attention and the third is combined, which is as it sounds, a combination of both subtypes. 

Autism spectrum disorder (ASD) is a developmental disability caused by differences in the brain. The main symptoms of Autism are often problems with social communication and interaction and restricted or repetitive behaviours or interests. People with Autism may also have different ways of learning, moving, or paying attention than those without the condition.

Both conditions affect the central nervous system, which is responsible for movement, language, memory, focusing and social skills. They can both also cause social challenges but often the differentiating factors are usually the reasons behind the behaviours. The root causes for someone with ADHD may include inattention, impulsivity, and difficulty in organising their thoughts. Whereas, for autistic individuals, the reasons may be that they do not understand nonverbal communication or have delays in language skills. 

Research and studies into the relationship between ADHD and Autism

There are a growing number of genetic studies supporting the notion of some shared causation between ADHD and autism, including imaging studies comparing brain structures and connectivity. Using the core diagnostic criteria DSM-5, distinct impairments can be observed in both but some of the strongest evidence comes from the studies between families and twins and other relatives of people with either condition.

In a 2014 study conducted on firstborn children of women with ADHD, a sixfold risk of also having the condition was apparent and more than double the risk of having autism. Another study carried out in 2017, where a medical data review was carried out on around 2 million people born in Sweden, found that individuals with autism and their extended family members have an elevated risk of ADHD, with ADHD risk highest among identical twins of people with autism and is even elevated in cousins.

How to gain a diagnosis of ADHD and Autism

Gaining a diagnosis for either ADHD or Autism is both an intricate and lengthy process and tests and evaluations are not yet substantial enough to identify definitive links between the two. 

An ADHD assessment can be obtained through the NHS which usually includes a period of “watchful waiting” for children, lasting around 10 weeks to see if the condition worsens, improves, or stays the same. If the condition does not improve then a referral to a child specialist for a formal assessment will be granted. For adults, your GP will usually assess your symptoms and you may be referred to a specialist if you are thought to have had ADHD as a child and your symptoms are now causing moderate to severe functional impairment. Diagnosis is gained through a mixture of physical examinations, and interviews with both the person being assessed and significant people in their life. Children must also show 6 or more symptoms of inattentiveness or 6 or more symptoms of hyperactivity and impulsiveness in 2 different settings.

For adults to gain an ADHD diagnosis is more difficult as there is a dispute about whether the list of symptoms used to diagnose children, applies to adults. Adults may be diagnosed with ADHD if they present 5 or more symptoms of inattentiveness or 5 or more symptoms of hyperactivity and impulsiveness. However, it is difficult for a specialist to diagnose an adult with ADHD under the current diagnostic guidelines unless your symptoms have been present since childhood. 

Extensive research is continuously carried out around the overlap between ADHD and autism and although there is not one singular test to gain an accurate diagnosis, there are times when it can be useful to put aside the diagnostic debate and focus instead on addressing the child or the adult’s issues. In doing so, it could lead to a more accurate diagnosis.

Medication and treatment for ADHD and Autism

There are many forms of medication today that can help with both ADHD and Autism, unfortunately, there is not one specific medication designed to solely treat both conditions together. 

ADHD medications such as Methylphenidate are a stimulant and can significantly help to increase brain activity, particularly in areas that play a part in controlling attention and behaviour. Selective serotonin reuptake inhibitors (SSRIs) are commonly used with people presenting Autism. They are a group of antidepressants that treat imbalances in the body’s chemical systems, helping to reduce the frequency and intensity of repetitive behaviours, decrease anxiety, irritability, tantrums, and aggressive behaviour and improve eye contact.

There is no medication out there that provides a cure for either ADHD or Autism, rather they treat the symptoms that come with both conditions. Before or after a definitive diagnosis, behavioural therapies can help along with several other interventions such as speech therapy, occupational therapy, educational interventions and parent training. 

Specialists and psychiatrists believe that ADHD and Autism are two separate and distinct conditions that happen to be found together frequently and they are two lifelong conditions that affect every moment of their lives. Speaking to an ADHD and Autism specialist can be the first step in discovering how to lead an easier and happier life if you believe yourself or your child is suffering from either ADHD, Autism or both.

Speak to a specialist ASD and ADHD clinic

At Sanctum, we specialise in comprehensive, multi-professional care for children, adolescents and adults who may have ADHD and/ or Autism Spectrum Disorder (ASD). Our diagnostic team all have specialist experience in assessing and supporting individuals with ADHD and ASD and our service far surpasses the speed and level of care that you will find elsewhere. We provide rapid access and a very clear pathway for assessment, something which is difficult to obtain through the NHS.

Our goal is to help you be more effective in your day-to-day life and reduce the extent to which your possible ADHD and/ or ASD interferes with your happiness. Our assessment process leaves no stone unturned in understanding the nature of your condition and following your assessment we will provide recommendations for treatment such as medication optimisation, CBT interventions, psychology and coaching. Recommendations for adjustments in school, university and at work and regular follow-up appointments with a multidisciplinary team with continuity of care.

If you believe that you or your child may be suffering from ADHD or ASD, get in touch with us anytime for a confidential assessment.

Related Tags


Recommended articles

Get your first free online consultation