Attention Deficit Hyperactivity Disorder

Attention deficit hyperactivity disorder (ADHD) is a condition that affects behaviour. It develops in childhood and can continue into adulthood. Find out more about what ADHD is, the symptoms in both children and adults, and how the condition can be managed and treated.

What is ADHD?

ADHD is a neurodevelopmental disorder that can cause inattentiveness, hyperactivity, and impulsiveness. People with ADHD may seem restless, have a short attention span and difficulty concentrating, and act impulsively or recklessly.

The symptoms of ADHD are usually first noticed at an early age and most cases are diagnosed when children are six to 12 years old. However, some people may initially be misdiagnosed with another mental health condition such as bipolar disorder, or remain without a proper diagnosis until adulthood.

Many children can go through stages where they’re restless or have difficulty paying attention, but they don’t necessarily have ADHD. It’s important to speak to a health professional to discuss a diagnosis if a child may be affected.

The symptoms usually improve with age, but many adults will continue to experience problems and some may develop additional psychiatric disorders, most frequently mood and anxiety disorders, substance use disorders, or personality disorders. For example, ADHD and anxiety disorders have a 25% rate of occurring together, and co-occurrence with a reading disorder is also common.

What are the main types of ADHD?

People with ADHD may have problems with inattentiveness, hyperactivity, and impulsiveness, but not necessarily all three. There is a related condition, known as attention deficit disorder (ADD), which can cause problems with inattentiveness without the accompanying hyperactivity or impulsiveness associated with ADHD.

How many people have ADHD?

The reported rates of ADHD differ globally, ranging from 1% of school-age children in some countries to nearly 20% in others. The reason for this wide range of reported rates is unclear, but some experts claim it may be related to different case definitions.

An analysis of 175 research studies worldwide on ADHD prevalence in children aged 18 and under found an overall estimate of 7.2%. Screening of 11,422 adults aged 18–44 for ADHD in 10 countries in the Americas, Europe, and the Middle East showed an average prevalence of 3.4%.


The main symptoms of ADHD are related to inattentiveness, hyperactivity, and impulsiveness.

What are the symptoms of ADHD?

People with ADHD can have symptoms related to inattentiveness, hyperactivity, and impulsiveness but not necessarily all three. Symptoms can include:


  • Having a short attention span; being easily distracted
  • Overlooking details; making careless mistakes
  • Being forgetful in daily activities and losing things
  • Having difficulty completing long and tedious tasks
  • Starting new tasks or projects before completing others
  • Not listening properly to other people
  • Having difficulty in following instructions

Hyperactivity and impulsiveness:

  • Always moving or fidgeting; being constantly active
  • Being unable to play or enjoy hobbies quietly
  • Acting without thinking and having little or no sense of danger
  • Talking a lot and speaking out of turn
  • Interrupting or intruding on other people or conversations

These symptoms can lead to developmental issues such as poor educational achievement, problems with discipline, and a lack of social interaction.

What are the stages of ADHD?

Symptoms of ADHD are usually first seen at an early age and may become more noticeable as children start attending school. As children develop into adolescence, their hyperactivity may reduce; however, many will struggle with relationships and will display anti-social behaviours.

Inattention, restlessness, and impulsivity usually reduce with age, but many adults continue to experience problems.

One study found that almost half of people who had childhood ADHD continued to meet the full criteria for adult ADHD. Symptoms of inattention persisted in adults far more than hyperactivity/impulsivity. In adults, hyperactivity is more often internalised, and symptoms of inattention may be masked by anxiety symptoms or obsessive-like compensation strategies.

What are the early signs of ADHD?

Hyperactivity and impulsiveness tend to be the main symptoms in children; this includes fidgeting, a short attention span, and being unable to play quietly.

Causes and risk factors

The exact cause of ADHD is unknown. However, research has identified a number of factors that increase the risk of a child developing the condition.

What causes ADHD?

There are thought to be several risk factors for ADHD, including:

  • A family’s genes
  • Drinking alcohol, smoking, or using drugs during pregnancy
  • Exposure to environmental toxins, such as high levels of lead, during pregnancy
  • Premature birth (before the 37th week of pregnancy) and low birth weight
  • Being exposed to environmental toxins at a young age
  • Brain injuries

Is ADHD hereditary?

Genes passed down from parents will be a significant factor in a child developing the condition. However, in most cases, ADHD is linked to several genetic and environmental risk factors that each have a small individual effect and act together to increase susceptibility.

Who gets ADHD?

Because there is no single cause for ADHD, anyone can develop the condition. It develops in childhood and it can run in families.

How long can you live with ADHD?

ADHD does not directly reduce life expectancy, but throughout an individual’s lifetime, ADHD can increase the risk of other psychiatric disorders and have a significant impact on overall quality of life. However, while ADHD can’t be cured, the treatments available should provide some relief from its symptoms.


There is no single test to diagnose ADHD, and its symptoms can be similar to those of other behavioural issues; this may lead to a delayed diagnosis.

How is ADHD diagnosed?

A diagnosis of ADHD can only be made following a comprehensive evaluation by a clinician with expertise in the condition. The symptoms must have been long-lasting and must impact on the individual’s day-to-day life.

Tests to diagnose ADHD

ADHD can’t be diagnosed through a simple physical or psychological test. A specialist needs to carry out a detailed assessment to make a diagnosis. The assessment may include:

  • A physical examination (this can also help assess whether the symptoms are being caused by a different condition)
  • Face-to-face conversations with the child or adult being assessed
  • Direct conversations or reports from other people who engage with the person being assessed, such as partners and teachers

ADHD was originally defined in children but is now recognised to persist into adulthood for some patients. Despite this, adult ADHD remains underdiagnosed. A diagnosis can be complicated by symptoms that overlap with other psychiatric disorders that might occur alongside ADHD. Screening tools have been developed for clinicians to identify which adults should be evaluated for ADHD, and clinical interviews and family histories allow for differentiation between ADHD and other psychiatric conditions that can occur at the same time.

Treatment and medication

Treatment and medication for ADHD can help to relieve the symptoms and make the condition easier to live with.

How is ADHD treated?

Although there’s no cure for ADHD, affected children and their parents can be given educational and wider support, advice, and guidance, alongside medical and behavioural therapies, to help them manage the effects of the condition.
For adults, medication is often the first line of treatment, with additional support from psychological therapy.


A range of different medications may be used to help people manage the symptoms of ADHD. Doctors often need to work with individual patients to find the right medication or dosage that works for them. Most medications for ADHD can be classified either as stimulants or as non-stimulants.

  • Stimulants:These are the most common type of medication for ADHD. They work by increasing the chemicals dopamine and norepinephrine in the brain, which play a key role in managing thinking and attention
  • Non-stimulants:Medications that are non-stimulants can also be used to treat ADHD. They may be helpful for people for whom stimulants are not suitable. These medications can also improve focus, attention, and impulsivity in a person with ADHD. They may be prescribed in combination with a stimulant to increase effectiveness.
Some anti-depressants may also be used alone or in combination with a stimulant to treat ADHD. Anti-depressants may help all the symptoms of ADHD and can be prescribed if a stimulant is not appropriate, or they can be helpful in combination with stimulants if a patient also has another condition such as an anxiety disorder.

Medications for ADHD, like all prescription drugs, should be used under medical supervision.


A number of therapies can be useful in treating ADHD in children, young people, and adults.

  • Behavioural therapy: This can help someone with managing their own behaviour. Therapists can teach children social skills and how to respond appropriately to people. Behavioural therapists can also provide support for carers and teachers of children with ADHD.
  • Cognitive behavioural therapy (CBT):This can help with mindfulness – being aware and accepting of thoughts and feelings. This can help improve focus and concentration and reduce the urge to act without thinking or to take unnecessary risks.
  • Family therapy/parenting skills:Learning these can help family members find better ways to handle disruptive behaviours and encourage positive changes.
  • Support groups: These can help parents and families connect with others who have similar problems and concerns.


People with ADHD should try to eat a normal, healthy, balanced diet.

Some people with ADHD find that their symptoms seem to worsen after eating certain types of food or drink, especially those that contain additives or caffeine. In this case, it is advisable to keep a diary of food, drink and behaviour, and talk to a doctor. They may make a referral to a nutritionist or dietitian.


Children with ADHD should be supported to enjoy activities such as going for a walk, playing in the garden, or taking part in team sports. As well as promoting their physical health, regular exercise during the day will help make sure they are tired at bedtime.

To help children settle at bedtime, it’s important that they only take part in quiet activities in the evening that don’t overstimulate them.


While it is not possible to prevent ADHD, there are ways to reduce the impact of its symptoms. For example, parents and carers of children with ADHD can:
  • Set clear boundaries and expected behaviours
  • Keep to fixed routines, including at bedtime
  • Reward their child when they demonstrate positive behaviours and follow instructions (keep these simple and easy to follow)
  • Use stickers on a chart to show when the child has demonstrated positive behaviours; use this to track through the week so they can earn a reward
  • Get to know their child’s behaviours and intervene in a situation where they are becoming frustrated. This can include limiting time playing with friends if they may get overexcited
  • Speak to other carers for their child, for example teachers, to ensure they are given any extra support they need
Adults with ADHD can also use a number of techniques to help manage their symptoms:
  • Keep physically active and exercise regularly
  • Make time for relaxation
  • Make lists and use a diary to help stay organised

Scientific studies

Research is continuing into the potential risks for developing ADHD. Advanced imaging technology has identified structural and functional differences in the brain between individuals with and without ADHD. The underlying brain anatomical and functional measures, as well as familial/genetic factors, are major foci of neuropsychiatric research.

Recent studies have suggested an important role of the gut-brain axis (GBA) and intestinal microbiota in modulating the risk of ADHD. It is thought that key biological mechanisms involved in the GBA may increase the risk of developing ADHD.

Work is also underway to help health professionals make decisions on the best courses of treatment for individuals. A review has been completed on the efficacy and safety of the expanding number of treatments available, including pharmacological and dietary interventions.

Referenced sources

  1.  Katzman MA, Bilkey TS, Chokka PR, Fallu A, Klassen LJ. Adult ADHD and comorbid disorders: clinical implications of a dimensional approach. BMC Psychiatry. 2017;17(1):302. doi:10.1186/s12888-017-1463-3
  2.  D’Agati E, Curatolo P, Mazzone L. Comorbidity between ADHD and anxiety disorders across the lifespan. Int J Psychiatry Clin Pract. 2019;23(4):238-244. doi:10.1080/13651501.2019.1628277
  3.  Germanò E, Gagliano A, Curatolo P. Comorbidity of ADHD and dyslexia. Dev Neuropsychol. 2010;35(5):475-493. doi:10.1080/87565641.2010.494748
  4.  Polanczyk G, de Lima MS, Horta BL, Biederman J, Rohde LA. The worldwide prevalence of ADH: a systematic review and metaregression analysis. Am J Psychiatry. 2007;164(6):942-948. doi:10.1176/ajp.2007.164.6.942
  5.  Thomas R, Sanders S, Doust J, Beller E, Glasziou P. Prevalence of attention-deficit/hyperactivity disorder: a systematic review and meta-analysis. Pediatrics. 2015;135(4):e994-e1001. doi:10.1542/peds.2014-3482
  6.  Fayyad J, de Graaf R, Kessler R et al. Cross-national prevalence and correlates of adult attention-deficit hyperactivity disorder. Br J Psychiatry. 2007;190(5):402-409. doi:10.1192/bjp.bp.106.034389
  7.  Kessler RC, Green JG, Adler LA et al. Structure and diagnosis of adult attention-deficit/hyperactivity disorder: analysis of expanded symptom criteria from the Adult ADHD Clinical Diagnostic Scale. Arch Gen Psychiatry. 2010;67(11):1168-1178. doi:10.1001/archgenpsychiatry.2010.146
  8.  Weibel S, Menard O, Ionita A et al. Practical considerations for the evaluation and management of attention deficit hyperactivity disorder (ADHD) in adults. Encephale. 2020;46(1):30-40. doi:10.1016/j.encep.2019.06.005
  9.  Faraone SV, Asherson P, Banaschewski T et al. Attention-deficit/hyperactivity disorder. Nat Rev Dis Primers. 2015;1:15020. doi:10.1038/nrdp.2015.20
  10.  Jain R, Jain S, Montano CB. Addressing diagnosis and treatment gaps in adults with attention-deficit/hyperactivity disorder. Prim Care Companion CNS Disord. 2017;19(5):17nr02153. doi:10.4088/PCC.17nr02153
  11.  Friedman LA, Rapoport JL. Brain development in ADHD. Curr Opin Neurobiol. 2015;30:106-11. doi: 10.1016/j.conb.2014.11.007
  12.  Dam SA, Mostert JC, Szopinska-Tokov JW, Bloemendaal M, Amato M, Arias-Vasquez A. The role of the gut–brain axis in attention-deficit/hyperactivity disorder. Gastroenterol Clin North Am. 2019;48(3):407-431. doi:10.1016/j.gtc.2019.05.001
  13.  Caye A, Swanson JM, Coghill D, Rohde LA. Treatment strategies for ADHD: an evidence-based guide to select optimal treatment. Mol Psychiatry. 2019;24(3):390-408. doi:10.1038/s41380-018-0116-3
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