What is ADHD?


Attention deficit hyperactivity disorder (ADHD) is a developmental neuropsychiatric disorder in which there are significant problems with executive functions (e.g., attentional control and inhibitory control) that cause attention deficits, hyperactivity, or impulsiveness which is not appropriate for a person’s age.

These symptoms must begin by age six to twelve and persist for more than six months for a diagnosis to be made. In school-aged individuals inattention symptoms often result in poor school performance. Although it causes impairment, particularly in modern society, many children with ADHD have a good attention span for tasks they find interesting.

Despite being the most commonly studied and diagnosed psychiatric disorder in children and adolescents, the cause in the majority of cases is unknown. It affects about 6–7% of children when diagnosed via the DSM-IV criteria and 1–2% when diagnosed via the ICD-10 criteria. Rates are similar between countries and depend mostly on how it is diagnosed. ADHD is diagnosed approximately three times more in boys than in girls. About 30–50% of people diagnosed in childhood continue to have symptoms into adulthood and between 2–5% of adults have the condition. The condition can be difficult to tell apart from other disorders as well as that of high normal activity.

ADHD management usually involves some combination of counseling, lifestyle changes, and medications. Medications are only recommended as a first-line treatment in children who have severe symptoms and may be considered for those with moderate symptoms who either refuse or fail to improve with counseling. Stimulant therapy is not recommended in preschool-aged children. Treatment with stimulants is effective for up to 14 months; however, its long term effectiveness is unclear. Adolescents and adults tend to develop coping skills which make up for some or all of their impairments.

ADHD, its diagnosis, and its treatment have been considered controversial since the 1970s. The controversies have involved clinicians, teachers, policymakers, parents, and the media. Topics include ADHD’s causes and the use of stimulant medications in its treatment. Most healthcare providers accept ADHD as a genuine disorder, and the debate in the scientific community mainly centers on how it is diagnosed and treated.

ADHD Signs and Symptoms

Inattention, hyperactivity (restlessness in adults), disruptive behavior, and impulsivity are common in ADHD. Academic difficulties are frequent as are problems with relationships. The symptoms can be difficult to define as it is hard to draw a line at where normal levels of inattention, hyperactivity, and impulsivity end and significant levels requiring interventions begin.

To be diagnosed per DSM-5, symptoms must be observed in multiple settings for six months or more and to a degree that is much greater than others of the same age. They must also cause problems in the person’s social, academic, or work life.

Based on the presenting symptom ADHD can be divided into three subtypes: predominantly inattentive, predominantly hyperactive-impulsive, and combined type.

An individual with inattention may have some or all of the following symptoms:

  • Be easily distracted, miss details, forget things, and frequently switch from one activity to another

  • Have difficulty maintaining focus on one task

  • Become bored with a task after only a few minutes, unless doing something enjoyable

  • Have difficulty focusing attention on organizing and completing a task or learning something new

  • Have trouble completing or turning in homework assignments, often losing things (e.g., pencils, toys, assignments) needed to complete tasks or activities

  • Not seem to listen when spoken to

  • Daydream, become easily confused, and move slowly

  • Have difficulty processing information as quickly and accurately as others

  • Struggle to follow instructions

An individual with hyperactivity may have some or all of the following symptoms:

  • Fidget and squirm in their seats

  • Talk nonstop

  • Dash around, touching or playing with anything and everything in sight

  • Have trouble sitting still during dinner, school, doing homework, and story time

  • Be constantly in motion

  • Have difficulty doing quiet tasks or activities

These hyperactivity symptoms tend to go away with age and turn into “inner restlessness” in teens and adults with ADHD.

An individual with impulsivity may have some or all of the following symptoms:

  • Be very impatient

  • Blurt out inappropriate comments, show their emotions without restraint, and act without regard for consequences

  • Have difficulty waiting for things they want or waiting their turns in games

  • Often interrupt conversations or others’ activities

People with ADHD more often have difficulties with social skills, such as social interaction and forming and maintaining friendships. This is true for all subtypes. About half of children and adolescents with ADHD experience social rejection by their peers compared to 10–15% of non-ADHD children and adolescents. People with ADHD have attention deficits which cause difficulty processing verbal and nonverbal language which can negatively affect social interaction. They also may drift off during conversations, and miss social cues.

Difficulties managing anger are more common in children with ADHD as are poor handwriting and delays in speech, language and motor development.

Causes of ADHD

The cause of most cases of ADHD is unknown; however, it is believed to involve interactions between genetic and environmental factors. Certain cases are related to previous infection of or trauma to the brain.


Twin studies indicate that the disorder is often inherited from one’s parents with genetics determining about 75% of cases. Siblings of children with ADHD are three to four times more likely to develop the disorder than siblings of children without the disorder. Genetic factors are also believed to be involved in determining whether ADHD persists into adulthood.

Typically, a number of genes are involved, many of which directly affect dopamine neurotransmission. Those involved with dopamine include DAT, DRD4, DRD5, TAAR1, MAOA, COMT, and DBH. Other genes associated with ADHD include SERT, HTR1B, SNAP25, GRIN2A, ADRA2A, TPH2, and BDNF. A common variant of a gene called LPHN3 is estimated to be responsible for about 9% of cases and when this gene is present, people are particularly responsive to stimulant medication.

As ADHD is common, natural selection likely favored the traits, at least individually, and they may have provided a survival advantage. For example, some women may be more attracted to males who are risk takers, increasing the frequency of genes that predispose to ADHD in the gene pool. As it is more common in children of anxious or stressed mothers, some argue that ADHD is an adaptation that helps children face a stressful or dangerous environment with, for example, increased impulsivity and exploratory behavior.

Hyperactivity might have been beneficial, from an evolutionary perspective, in situations involving risk, competition, or unpredictable behavior (i.e. exploring new areas or finding new food sources). In these situations, ADHD could have been beneficial to society as a whole even while being harmful to the individual. Additionally, in certain environments it may have offered advantages to the individuals themselves, such as quicker response to predators or superior hunting skills.


Environmental factors are believed to play a lesser role. Alcohol intake during pregnancy can cause fetal alcohol spectrum disorder which can include symptoms similar to ADHD. Exposure to tobacco smoke during pregnancy can cause problems with central nervous system development and can increase the risk of ADHD. Many children exposed to tobacco do not develop ADHD or only have mild symptoms which do not reach the threshold for a diagnosis. A combination of a genetic predisposition with tobacco exposure may explain why some children exposed during pregnancy may develop ADHD and others do not. Children exposed to lead, even low levels, or polychlorinated biphenyls may develop problems which resemble ADHD and fulfill the diagnosis. Exposure to the organophosphate insecticides chlorpyrifos and dialkyl phosphate is associated with an increased risk; however, the evidence is not conclusive.

Very low birth weight, premature birth and early adversity also increase the risk, as do infections during pregnancy, at birth, and in early childhood. These infections include, among others, various viruses (measles, varicella, rubella, enterovirus 71) and streptococcal bacterial infection. At least 30% of children with a traumatic brain injury later develop ADHD and about 5% of cases are due to brain damage.

Some children may react negatively to food dyes or preservatives. It is possible that certain food coloring may act as a trigger in those who are genetically predisposed but the evidence is weak. The United Kingdom and European Union have put in place regulatory measures based on these concerns; the FDA has not.


The diagnosis of ADHD can represent family dysfunction or a poor educational system rather than an individual problem. Some cases may be explained by increasing academic expectations, with a diagnosis being a method for parents in some countries to get extra financial and educational support for their child. The youngest children in a class have been found to be more likely to be diagnosed as having ADHD possibly due to their being developmentally behind their older classmates. Behavior typical of ADHD occurs more commonly in children who have experienced violence and emotional abuse.

Per social construction theory it is societies that determine the boundary between normal and abnormal behavior. Members of society, including physicians, parents, and teachers, determine which diagnostic criteria are used and, thus, the number of people affected. This leads to the current situation where the DSM-IV arrives at levels of ADHD three to four times higher than those obtained with the ICD-10. Thomas Szasz, a supporter of this theory, has argued that ADHD was “invented and not discovered.”


The management of ADHD typically involves counseling or medications either alone or in combination. While treatment may improve long-term outcomes, it does not get rid of negative outcomes entirely.

Medications used include stimulants, atomoxetine, alpha-2 adrenergic receptor agonists, and sometimes antidepressants. Dietary modifications may also be of benefit with evidence supporting free fatty acids and reduced exposure to food coloring. Removing other foods from the diet is not currently supported by the evidence.

Behavioral Therapies

There is good evidence for supporting the use of behavioral therapies in ADHD and they are the recommended first line treatment in those who have mild symptoms or are preschool-aged. Psychological therapies used include: psychoeducational input, behavior therapy, cognitive behavioral therapy (CBT), interpersonal psychotherapy, family therapy, school-based interventions, social skills training, parent management training, and neurofeedback. Parent training and education have been found to have short-term benefits. There is little high quality research on the effectiveness of family therapy for ADHD, but the evidence that exists shows that it is similar to community care and better than a placebo. Several ADHD specific support groups exist as informational sources and may help families cope with ADHD.

Training in social skills, behavioral modification and medication may have some limited beneficial effects. The most important factor in reducing later psychological problems, such as major depression, criminality, school failure, and substance use disorders is formation of friendships with people who are not involved in delinquent activities.

Regular physical exercise, particularly aerobic exercise, is an effective add on treatment for ADHD, although the best type and intensity is not currently known. In particular, physical exercise has been shown to result in better behavior and motor abilities without causing any side effects.


Stimulant medications are the pharmaceutical treatment of choice. They have at least some effect in the short term in about 80% of people.

There are a number of non-stimulant medications, such as atomoxetine, bupropion, guanfacine, and clonidine that may be used as alternatives. There are no good studies comparing the various medications; however, they appear more or less equal with respect to side effects. Stimulants appear to improve academic performance while atomoxetine does not. There is little evidence on their effects on social behaviors. Medications are not recommended for preschool children, as the long-term effects in this age group are not known.

The long-term effects of stimulants generally are unclear with one study finding benefit, another finding no benefit and a third finding evidence of harm. Magnetic resonance imaging studies suggest that long-term treatment with amphetamine or methylphenidate decreases abnormalities in brain structure and function found in subjects with ADHD. Atomoxetine, due to its lack of abuse potential, may be preferred in those who are at risk of abusing stimulant medication. Guidelines on when to use medications vary by country, with the United Kingdom’s National Institute for Health and Care Excellence recommending use only in severe cases, while most United States guidelines recommend medications in nearly all cases.

While stimulants and atomoxetine are usually safe, there are side-effects and contraindications to their use. Stimulants may result in psychosis or mania; however, this is relatively uncommon. Regular monitoring has been recommended in those on long-term treatment. Stimulant therapy should be stopped from time to assess for continuing need for medication. Stimulant medications have the potential for abuse and dependence; several studies indicate that untreated ADHD is associated with elevated risk of substance abuse and conduct disorders. The use of stimulants appears to either reduce this risk or have no effect on it. The safety of these medications in pregnancy is unclear.


ADHD and its diagnosis and treatment have been considered controversial since the 1970s. The controversies have involved clinicians, teachers, policymakers, parents and the media. Positions regarding ADHD range from believing it is simply the far end of a normal range of behavior to considering that it is the result of an underlying genetic condition.

Other areas of controversy include the use of stimulant medications and specifically their use in children, as well as the method of diagnosis and the possibility of overdiagnosis. In 2012, the National Institute for Health and Care Excellence, while acknowledging the controversy, states that the current treatments and methods of diagnosis are based on the dominant view of the academic literature. In 2014, Keith Conners, one of the early advocates for recognition of the disorder, spoke out against overdiagnosis in a NY Times article. In contrast, a 2014 peer-reviewed medical literature review indicated that ADHD is underdiagnosed in adults.

With widely differing rates of diagnosis across countries, states within countries, races, and ethnicities, some suspect factors other than the presence of the symptoms of ADHD are playing a role in diagnosis. Some sociologists consider ADHD to be an example of the medicalization of “deviant behavior”, or in other words, the turning of the previously non-medical issue of school performance into a medical one. Most healthcare providers accept ADHD as a genuine disorder, at least in the small number of people with severe symptoms. Among healthcare providers the debate mainly centers on diagnosis and treatment in the much larger number of people with less severe symptoms.

As of 2009, 8% of all United States Major League Baseball players had been diagnosed with ADHD, making the disorder common among this population. The increase coincided with the League’s 2006 ban on stimulants, which has raised concern that some players are mimicking or falsifying the symptoms or history of ADHD to get around the ban on the use of stimulants in sport.

Further Reading:

Cimera, Robert E. (2002). Making ADHD a Gift: Teaching Superman How to Fly. Lanham, Md.: Scarecrow Press

National Collaborating Centre for Mental Health (2008). Attention Deficit Hyperactivity Disorder: The NICE Guideline on Diagnosis and Management of ADHD in Children, Young People and Adults British Psychological Society and RCPsych Publications

Ramsay JR (2007). Cognitive-Behavioral Therapy for Adult ADHD: An Integrative Psychosocial and Medical Approach . Routledge

New Zealand Guidelines for the Assessment and Treatment of Attention-Deficit/ Hyperactivity Disorder

Malenka RC, Nestler EJ, Hyman SE (2009). Molecular Neuropharmacology: A Foundation for Clinical Neuroscience. New York: McGraw-Hill Medical

Clare Stanford, Rosemary Tannock (2014) Behavioral Neuroscience of Attention Deficit Hyperactivity Disorder and Its Treatment. New York: Springer