Patient information from BMJ

ADHD: what is it?

Last published:Jan 28, 2025

ADHD is a neurodevelopmental condition. People with ADHD may struggle with staying focused, feeling restless, or making impulsive decisions. Getting a proper diagnosis is important, and there are treatments available that can help manage the symptoms.

This information helps explain what ADHD is and how to recognise if you might have it.

What is ADHD?

ADHD stands for attention deficit hyperactivity disorder. ADHD is a neurodevelopmental condition, which means it affects how the brain develops and works. If you have ADHD, you might find it hard to focus, feel restless, or act on impulse without thinking it through.

Doctors aren’t sure what causes ADHD, but it seems to run in families. It may be due to a mix of genetic and external factors. It’s important to know that ADHD isn’t anyone’s fault. It’s not caused by anything you or your family did - factors like diet, schooling, or screen time do not cause ADHD.

If you have ADHD, you might find it hard to block out distractions. It can be difficult to focus on one task or stay organised. Everyday sounds, sights, and activities can feel overwhelming, making it hard to know what’s most important. This isn’t because you're being careless or trying to be difficult - ADHD is a medical condition.

ADHD symptoms often appear in childhood, and most children with ADHD are diagnosed by age 12. Many children with ADHD continue to experience it as adults. Sometimes, ADHD isn’t noticed in childhood and is only identified in adulthood.

You might hear ADHD called by other names. In the past, doctors called it ‘attention deficit disorder’ or ‘hyperactivity’. Some doctors may still use these terms, as well as ‘hyperkinetic disorder’ or HKD for short.

What are the symptoms of ADHD?

The main symptoms of ADHD are struggling to pay attention, being overactive, and being impulsive. Here are some examples of these types of behaviour.

Being inattentive

Being inattentive means having difficulty focusing or paying attention. This might include:

• Missing details or making simple mistakes in work or schoolwork

• Finding it hard to concentrate on a task, or avoiding tasks that require lots of concentration

• Finding it hard to follow through on instructions, or finish a task

• Finding it hard to organise tasks and activities

• Losing things frequently

• Getting easily distracted

• Being forgetful in daily activities.

Being hyperactive

Being hyperactive or overactive means feeling restless or unable to stay still. This might include:

• Fidgeting or tapping hands and feet

• Running or climbing in inappropriate settings (in children)

• Leaving your seat in situations where sitting down is expected

• Being unable to stay still for long periods, such as at mealtimes or during classes or meetings

• Having trouble enjoying leisure activities quietly

• Talking excessively.

Being impulsive

Being impulsive means acting quickly without thinking, often without considering the consequences. This can include:

• Answering before a question is finished, or completing other people’s sentences

• Interrupting in conversations

• Intruding on activities, or using other people’s things without their permission

• Finding it hard to wait your turn for activities

• Doing risky things, like running across roads (in children) or engaging in thrill-seeking activities.

Some people with ADHD have all of these symptoms, while others are either mostly inattentive or mostly hyperactive and impulsive.

If you experience most of these symptoms, you should talk to your doctor. They will arrange to have you assessed for ADHD.

How do doctors diagnose ADHD?

There is no scan or test to tell if a child has ADHD. Doctors diagnose ADHD by looking at the symptoms and how many there are. They might refer you to someone who is specially trained to diagnose ADHD.

Doctors are very careful about diagnosing ADHD. A wrong diagnosis can be harmful, because it might lead to treatment that isn’t needed. So, diagnosing ADHD takes time. Your doctor or specialist will check to see you if meet the criteria for ADHD. This means that:

• you must have six or more symptoms of inattention, or six or more symptoms of being overactive and acting before thinking 

• the symptoms started before you were 12 years old

• the symptoms have been happening for at least 6 months

• the symptoms happen in at least two different places, like home, school, or work

• the symptoms negatively affect your daily life

• the symptoms aren’t caused by another disorder, like anxiety for example.

Your doctor will ask you questions about your behaviour, but it’s not usually possible to diagnose ADHD based on your own description of symptoms. When ADHD is diagnosed in childhood, doctors gather information from parents, caregivers, or teachers about behaviour. In adulthood, doctors will ask family, friends, or others who know you well for information about your behaviour.

Your doctor might also carry out other tests to rule out any other medical conditions. Some people with ADHD have other neurodevelopment conditions like autism spectrum disorder or dyslexia.

Many people with ADHD also have a mental health condition, such as anxiety or a mood disorder. If you also have a mental health condition, this will be treated separately.

What happens next?

Learning that you have ADHD might feel overwhelming at first. You might also feel relieved, as it might help explain certain behaviours or struggles you’ve experienced. There’s no ‘cure’ for ADHD, but there are different treatments and strategies that can help you manage it.

The main treatment for ADHD is a combination of medicine and talking treatments. Many people find that these treatments make a big difference in managing ADHD. To read more about treatments, see our patient information titled: ADHD: what are the treatment options?

Some children with ADHD find their symptoms improve as they get older, but many continue to experience ADHD into adulthood. With the right treatment and support, most people are able to manage ADHD in their daily life.

Where to get more help

There are many charities and support groups for people with ADHD and their families. Your doctor may be able to help you find one in your area, or you could search online. These groups often have useful resources and services and can connect you with others who are going through a similar experience.