The United Kingdom is experiencing dramatic increases in requests for diagnosis of attention deficit hyperactivity disorder (ADHD) in adults. But what is ADHD, and why is it suddenly becoming something the general public and medical professionals need to be aware of? In this feature, Dr. James Brown and Dr. Alex Conner provide some context.

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Is adult ADHD on the rise? Marko Geber/Getty Images

National Teaching Fellow Dr. Conner is a reader in biomedical science communication at the College of Medical and Dental Sciences at the University of Birmingham, U.K. Dr. Brown is a reader in biomedical science at the College of Health and Life Sciences at Aston University, U.K.

Together, they co-founded the charity ADHDadultUK in 2021 to improve the lives of adults with ADHD through psychoeducation, advocacy, and peer support.

ADHD is a lifelong neurodevelopmental disorder in which the brain grows differently. This leads to deficient action from the chemicals involved in pleasure and reward.

The name ADHD is a little unhelpful as those with the disorder do not have a deficit of attention, more a lack of ability to control what they pay attention to. Even the hyperactivity part isn’t always obvious, at least externally.

ADHD is commonly associated with issues with “executive function.” These are the higher thinking skills, such as planning, task management, cognitive inhibition, and working memory.

Although often seen as a “new” disorder predominantly seen in children, ADHD was first described in medical texts dating back to the 18th century. And although it is usually diagnosed during childhood, most people continue to live with ADHD for their entire adult lives.

Recently, a growing number of people are first reporting ADHD symptoms as adults, partly due to high-profile cases or the impact of social media.

In fact, somewhere around 2.8% of adults are thought to live with ADHD, with the vast majority of these being undiagnosed.

Despite this growing awareness, issues with healthcare resources, poor understanding among healthcare professionals, and stigma around the disorder mean many adults struggle to get a diagnosis.

The neurological basis for the disorder means ADHD brains often search for ways to stimulate the chemicals that have deficient action, which is why those with the disorder can experience some or all of the core traits: inattentiveness, hyperactivity, and impulsivity.

These core traits can manifest themselves in several ways, including:

  • Being unable to follow through on longer tasks or not being able to start them.
  • Being easily distracted by other tasks or thoughts.
  • Seeking out activities, sometimes including risky behaviors, that provide an immediate reward.
  • Restlessness, either externally or internally.
  • Interrupting other people without wanting to.

The symptoms of ADHD are largely similar for both adults and children, although ADHD can present differently as we age. For example, inattention is the most persistent symptom in adults, and hyperactivity is less apparent.

ADHD can be extremely debilitating if untreated. It has been associated with a higher likelihood of reduced quality of life, increased risk of substance use issues, unemployment or underemployment, accidental injuries, suicide, and premature death, among other issues.

In addition, untreated ADHD is thought to have significant costs to society, with estimates of around £18,000 —around $24,400 — each year per untreated ADHD adult. This is due to issues such as medical care and unemployment costs.

Beyond the core traits of ADHD, an array of commonly associated co-existing conditions are reported in ADHD adults.

These co-existing conditions include a greater than three-fold risk of mood disorders compared with non-ADHD adults, a twofold increased risk of having an anxiety disorder, and increased risks for eating disorders and obesity.

Additionally, around 70% of adults with ADHD also experience emotional dysregulation, making it difficult to control emotional responses. It is believed that almost all adults with ADHD have rejection sensitive dysphoria (RSD), a condition where real or even perceived rejection or criticism can cause extreme emotional sensitivity or pain.

As public awareness of adult ADHD increases, it has become apparent that receiving an ADHD diagnosis as an adult in the U.K. can be particularly difficult.

There have been reports in some areas of referral times of up to 5 years or more. These extensive waiting times are due to the requirement for a specialist psychiatrist diagnosis.

Even with a referral to a specialist, there are still challenges. The individual has to show clear evidence of a significant number of ADHD traits, evidence of these traits being present since childhood, and evidence that the disorder has a moderate impact on two separate areas of a person’s life, such as causing issues with work, education, or in maintaining relationships.

The surge in people seeking referrals means that even private clinics have extensive waiting periods for diagnosis.

While there is now a growing recognition of ADHD in adults, many people still live with it undiagnosed for any number of reasons: lack of awareness that ADHD in adults is a real thing, mishandling by healthcare professionals, or diagnosis hesitancy — the fear of being labeled with something that carries a stigma in society.

Understanding the condition in adults, taking it more seriously as a disorder, raising awareness of it both in society in general and among healthcare professionals, and investing in services to improve diagnosis times are essential to deal with this growing issue.

Improving access to diagnosis and reducing the stigma associated with ADHD would open the door to treatment, which can have a marked impact on living with the disorder — such as improving self-esteem, productivity, and quality of life.