ADHD abbreviation on wooden blocks. ADHD is Attention deficit hyperactivity disorder. Close up. Vignette.

Understanding attention deficit hyperactivity disorder (ADHD) in adults

Posted on: July 11, 2023

Attention deficit hyperactivity disorder (ADHD) is commonly associated with children, but it’s a condition that affects people of all ages. In fact, the National Institute for Health and Care Excellence suggests approximately 3% to 4% of adults in the United Kingdom have ADHD. However, many of these adults may be undiagnosed or misdiagnosed due to a lack of awareness and understanding of the condition in adults.

What is ADHD?

ADHD is a common neurodevelopmental disorder that affects people’s behaviour. For example, it can influence how well a person can:

  • pay attention
  • control their impulses
  • regulate their emotions.

For adults with ADHD, these challenges can seem particularly daunting because they’re accompanied by the demands of work, family, and social responsibilities.

Types of ADHD in adults

There are three commonly agreed-upon types of ADHD in both adults and children.


Inattentiveness is observed through difficulty concentrating and focusing. This type of ADHD is sometimes called attention deficit disorder (ADD), though the term has been used less frequently in recent years.

Symptoms of inattention ADHD can include problems with time management, an inability to complete tasks, distractibility, and procrastination.

Hyperactivity and impulsiveness

Hyperactivity and impulsiveness ADHD is observed through seemingly constant movement, talking, fidgeting, and so on.

Symptoms of hyperactivity or hyperactive-impulsive ADHD can include excessive movement, interruptions, and little to no sense of danger.

Combined ADHD

Combined ADHD, which includes both inattentive and hyperactivity symptoms, is the most commonly diagnosed type of attention deficit hyperactivity disorder. The prevalence of combined ADHD is estimated to be between 50% and 75% of all cases.

What are the most common ADHD symptoms in adults?

According to the NHS, the symptoms of ADHD in adults are more difficult to define because of a lack of research into adults with the disorder:

“As ADHD is a developmental disorder, it’s believed it cannot develop in adults without it first appearing during childhood. But symptoms of ADHD in children and teenagers often continue into adulthood,” the NHS website states. “The way in which inattentiveness, hyperactivity and impulsiveness affect adults can be very different from the way they affect children. For example, hyperactivity tends to decrease in adults, while inattentiveness tends to remain as the pressures of adult life increase.”

The NHS points out adult ADHD symptoms tend to be more subtle than the symptoms seen in childhood ADHD, but notes there are still some agreed symptoms associated with ADHD in adults. These include:

  • careless mistakes and lack of attention to detail
  • continually starting new tasks before finishing old ones
  • poor organisational skills
  • inability to focus or prioritise
  • continually losing or misplacing things
  • forgetfulness
  • restlessness and edginess
  • difficulty keeping quiet, and speaking out of turn
  • blurting out responses and often interrupting others
  • mood swings, irritability and a quick temper
  • inability to deal with stress
  • extreme impatience
  • taking risks in activities, often with little or no regard for personal safety or the safety of others – for example, driving dangerously.

Potential causes of ADHD

There is no conclusive evidence to prove the exact cause of ADHD, and research in this area continues. However, scientists tend to believe a combination of factors could be responsible for the disorder.

The NHS highlights some of these, including:

  • genetics, with ADHD often running in families
  • brain function and structure, with research identifying a number of possible differences when comparing the brains of people with ADHD to those of people without ADHD. The NHS also points out there are studies to suggest people with ADHD may have “an imbalance in the level of neurotransmitters in the brain, or that these chemicals may not work properly.”
  • at-risk groups, including people born prematurely (before a pregnancy’s 37th week) or with a low birthweight, people with epilepsy, and people with brain damage.

There are other potential causes too. For example, the Centers for Disease Control and Prevention (CDC) in the United States notes scientists continue to study other possible causes and risk factors. These include exposure to environmental risks (such as lead) during pregnancy or at a young age, and alcohol and tobacco use during pregnancy. The American Psychiatric Association also includes extreme stress during pregnancy in its list of possible non-genetic causes.

The CDC, meanwhile, emphasises that research does not support “the popularly held views that ADHD is caused by eating too much sugar, watching too much television, parenting, or social and environmental factors such as poverty or family chaos. Of course, many things, including these, might make symptoms worse, especially in certain people. But the evidence is not strong enough to conclude that they are the main causes of ADHD.”

What is the correlation between ADHD and substance abuse?

Several studies suggest that people with ADHD, particularly adolescents, are more likely than other young people to use drugs. Evidence-based reports also point out that young people with ADHD are at greater risk for developing substance use disorders.

How is ADHD in adults diagnosed?

Diagnosis of adult attention-deficit/hyperactivity disorder varies around the world. For example, in the United States, healthcare providers use the guidelines in the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders, Fifth edition (DSM-5) to help diagnose ADHD.

In the UK, though, there are a few steps on the path to diagnosis for ADHD in adulthood.

  • An appointment with a GP. The doctor will assess the individual’s symptoms to determine whether they should be referred for an assessment.
  • A formal assessment with a specialist. This assessment could be with a psychiatry professional or other mental health professional. It may also include a physical examination to rule out other potential causes for symptoms, a series of interviews with the individual being assessed, and interviews or reports from other invested parties, such as partners or other health care professionals.
  • A formal diagnosis. Depending on the outcome of the referral and assessment, an individual may be diagnosed with ADHD. In adults, however, diagnoses are more difficult to obtain because there isn’t a commonly agreed list of symptoms for adults. In fact, under the current diagnostic guidelines in the NHS, a diagnosis of ADHD cannot be confirmed in an adult unless their symptoms were present in childhood.

How is ADHD in adults treated?

Treatment of adult ADHD is similar to the treatment for children, and typically involves a mix of medicine and therapy.

ADHD medications approved for use in the UK include:

  • Methylphenidate
  • Lisdexamfetamine
  • Dexamfetamine
  • Atomoxetine
  • Guanfacine

These medications aim to reduce ADHD symptoms in different ways – for example, there are stimulants or amphetamines as well as non-stimulant medications – and have different associated side effects.

Therapeutic interventions, meanwhile, can include:

  • psychoeducation, which encourages discussion about ADHD and its effects
  • behaviour therapy, including behaviour management
  • talking therapies, such as psychotherapy or cognitive behavioural therapy (CBT), which can help people to reframe situations and better manage them.

Living with ADHD as an adult

There are a number of resources available to help adults manage their ADHD symptoms. This includes:

  • ADHD UK, which offers an adult ADHD self-screening tool and guidance for people who want to seek a private diagnosis
  • AADD-UK, a charity for adults with ADHD
  • regional support groups

It’s also important to remember people with ADHD are more likely to experience mental health conditions such as:

  • anxiety disorders
  • personality disorders
  • obsessive compulsive disorder
  • mood disorders such as bipolar disorder

This means it’s important to watch for signs or symptoms of mental health challenges so they can be treated as soon as possible. Other challenges associated with ADHD can include:

  • learning disabilities and impairments
  • academic or professional underachievement
  • low self-esteem.

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