Attention Deficit Hyperactivity Disorder (ADHD)

ADHD is a syndrome of inattention, hyperactivity, and impulsivity. There are three types of ADHD: predominantly inattentive, predominantly hyperactive/impulsive, and combined. Diagnosis is based on clinical criteria. Treatment typically includes pharmacotherapy with stimulants or other medications, behavioral therapy, and educational interventions.

Attention-deficit/hyperactivity disorder (ADHD) is a type of neurodevelopmental disorder. Neurodevelopmental disorders are neurologically based conditions that begin in early childhood, usually before school entry, and interfere with personal, social, academic, and/or occupational development. They typically involve difficulties acquiring, retaining, or applying specific skills or sets of information. Neurodevelopmental disorders may include one or more of the following: impaired attention, memory, perception, language, problem solving, or social interaction. Other common neurodevelopmental disorders include autism spectrum disorders , learning disorders (eg, dyslexia ), and intellectual disability .

Previously, some experts considered ADHD a conduct disorder, perhaps because children typically exhibit inattentive, impulsive, and overactive behavior, and because comorbid conduct disorders, particularly oppositional defiant disorder and conduct disorder , are common . However, ADHD has a well-established neurological basis and is not simply “misbehavior.”

ADHD is estimated to occur in 5–15% of children ( 1 ). However, many experts believe that ADHD is overdiagnosed, largely due to imprecise application of criteria. According to the Diagnostic and Statistical Manual of Mental Disorders , Fifth Edition , DSM-5-TR, there are 3 types:

• Mostly inattentive
• predominantly hyperactive/impulsive;
• Combined

Overall, ADHD is about twice as common in boys ( 2 ), although the rate varies by type. The predominantly hyperactive/impulsive type is more common in boys ( 3 ); the predominantly inattentive type occurs with about equal frequency in both sexes. ADHD tends to run in families.

ADHD has no known specific cause. Possible causes of ADHD include genetic, biochemical, sensorimotor, physiological, and behavioral factors. Some risk factors include birth weight < 1500 g, head trauma, iron deficiency , obstructive sleep apnea , and lead exposure , as well as prenatal exposure to alcohol, tobacco, and possibly cocaine ( 3 ). ADHD has also been associated with adverse childhood experiences ( 4 ). Less than 5% of children with ADHD have evidence of neurological damage. Increasing evidence suggests differences in the dopaminergic and noradrenergic systems, with decreased activity or stimulation of the upper brainstem and anterior-midbrain tracts ( 5 ).

General reference materials

1. 1. Boznovik K, McLamb F, O’Connell K, et al : US national, regional, and state-specific socioeconomic factors correlate with child and adolescent ADHD diagnoses. Sci Rep 11:22008, 2021. doi: 10.1038/s41598-021-01233-2
2. 2. Ayano G, Demelash S, Gizachew Y, Tsegay L, Alati R : The global prevalence of attention deficit hyperactivity disorder in children and adolescents: An umbrella review of meta-analyses.  J Affect Disord 339:860–866, 2023. doi:10.1016/j.jad.2023.07.071
3. 3. Morrow CE, Xue L, Manjunath S, et al : Estimated Risk of Developing Selected DSM-IV Disorders Among 5-Year-Old Children with Prenatal Cocaine Exposure.  J Child Fam Stud 18(3):356–364, 2009. doi:10.1007/s10826-008-9238-6
4. 4. Brown N, Brown S, Briggs R, et al : Associations between adverse childhood experiences and ADHD diagnosis and severity. Acad Pediatr 17(4):349–355, 2017. doi: 10.1016/j.acap.2016.08.013
5. 5. Del Campo N, Chamberlain SR, Sahakian BJ, Robbins TW : The roles of dopamine and noradrenaline in the pathophysiology and treatment of attention-deficit/hyperactivity disorder.  Biol Psychiatry 69(12):e145–e157, 2011. doi:10.1016/j.biopsych.2011.02.036

ADHD in adults

Although ADHD is considered a childhood disorder and always begins in childhood, the underlying neurophysiological differences persist into adulthood, and behavioral symptoms continue into adulthood in about half of cases. Although diagnosis may sometimes not be made until adolescence or adulthood, some manifestations have been detected as early as age 12.

In adults, symptoms include:

• Difficulty concentrating
• Difficulty performing tasks ( impaired executive functions [programming and control functions] )
• mood swings;
• impatience
• Difficulty in maintaining relationships

Hyperactivity in adults typically manifests as restlessness and fidgeting rather than the motor hyperactivity seen in young children. Adults with ADHD tend to be at higher risk of unemployment, have lower educational attainment, and have higher rates of substance abuse and crime. Traffic accidents and violations are more common.

ADHD is more difficult to diagnose in adults. Symptoms may be similar to those of mood disorders , anxiety disorders , and substance use disorders . Because self-reporting of childhood symptoms can be unreliable, clinicians may need to review school records or interview family members to confirm the presence of symptoms before age 12.

Adults with ADHD may benefit from the same types of stimulant medications that children with ADHD take. They may also benefit from counseling to improve time management and other coping skills.

Symptoms and Signs of ADHD

The disease often begins before age 4 and invariably before age 12. The peak age of diagnosis is 8–10 years, but in patients with the predominantly inattentive type, the syndrome may not be diagnosed until adolescence.

The main symptoms and signs of ADHD:

• Inattention
• Impulsiveness
• Hyperactivity

Inattention usually occurs when a child performs tasks that require alertness, quick reaction, visual perception and sustained concentration, as well as prolonged and purposeful perception of verbal information.

Impulsivity refers to hasty actions with negative potential (for example, children who run across the street without looking, teenagers and adults who suddenly quit school or work without thinking about the consequences).

Hyperactivity involves excessive motor activity. Children, especially younger ones, may have trouble sitting still in situations where this is expected (such as school or church). Older patients may simply be fidgety, restless, or talkative—sometimes to the point that others feel exhausted watching them.

The organic nature of the disorder interferes with the development of thinking, learning skills, the ability to reason and express one’s thoughts sequentially, motivation for school, and adaptation to social demands. Children with predominantly inattentive ADHD tend to perceive hands-on learning and have difficulty in passive learning situations that require continuous work and task completion.

Overall, about 20–60% of children with ADHD have a learning disability ( 1 ), but most children with ADHD have some school problems due to inattention (as a result of missing details) and impulsivity (as a result of answering a question without thinking).

Children with ADHD are characterized by the following psychological characteristics: poor social skills and relationships with peers, sleep disturbances, anxiety, dysphoria, depression and mood swings.

Although there is no specific physical examination or lab tests associated with ADHD, signs may include:

• Lack of coordination or clumsiness
• non-localized, unexpressed neurological symptoms;
• Perceptual-motor dysfunctions

Reference materials on symptoms

1. 1. Czamara D, Tiesler CM, Kohlböck G, et al : Children with ADHD symptoms have a higher risk for reading, spelling and math difficulties in the GINIplus and LISAplus cohort studies.  PLoS One 8(5):e63859, 2013. doi:10.1371/journal.pone.0063859

Diagnosis of ADHD

• Clinical criteria are based on the 5th revised edition of the guidelines.

The diagnosis of ADHD is clinical and based on a comprehensive medical, developmental, educational, and psychological assessment ( 1 ).

DSM-5-TR Diagnostic Criteria for ADHD

The DSM-5-TR diagnostic criteria include 9 symptoms and signs of inattention and 9 symptoms and signs of hyperactivity and impulsivity. For a diagnosis to be made using these criteria, ≥ 6 symptoms and signs from one or each group must be present. In addition, the symptoms must

• Occur frequently for ≥ 6 months
• More pronounced than expected given the child’s developmental level
• Occurs in at least 2 situations (e.g. at home and at school)
• Be present before age 12 (at least some symptoms)
• Interfere with functioning at home, school or work

Symptoms of inattention:

• Does not pay attention to details or makes careless mistakes in school work or other activities
• Has difficulty concentrating in school or during play
• It seems that the child does not listen when spoken to directly.
• Does not follow instructions or final tasks
• Has difficulty organizing tasks and activities
• Avoids, dislikes, or is unwilling to engage in activities that require sustained mental effort over long periods of time
• Often loses things needed for schoolwork or activities
• Easily distracted
• Forgetful in daily activities

Symptoms of hyperactivity and impulsivity:

• Frequently moves arms or legs or fidgets
• Often leaves his seat in class or other situations
• Frequently runs back and forth or climbs excessively when such activity is inappropriate
• Unable to play calmly
• Often when walking it acts as if it is controlled by an engine
• Often speaks excessively
• Often blurts out answers before questions are completed
• Often has difficulty waiting in line
• Often interrupts or interferes with others

Diagnosis of predominantly inattentive type requires ≥ 6 symptoms and signs of inattention. Diagnosis of hyperactive/impulsive type requires ≥ 6 symptoms and signs of hyperactivity and impulsivity. Diagnosis of combined type requires ≥ 6 symptoms and signs of each of the types – inattention and hyperactivity/impulsivity.

Other diagnostic factors

Differentiating between ADHD and other conditions can be difficult. Overdiagnosis must be avoided, and other conditions must be accurately identified. Many signs of ADHD are evident in preschool years and may also indicate communication problems that may occur in other neurodevelopmental disorders (e.g., autism spectrum disorders ) or in some learning disorders , anxiety , depression , or behavioral disorders .

Clinicians should assess whether the child is distracted by external factors (e.g., environmental stimuli) or internal factors (e.g., thoughts, worries, concerns). In later childhood, signs of ADHD become more pronounced; children with the hyperactive-impulsive type or combined type often exhibit prolonged involuntary movements of the lower extremities, motor agitation (e.g., aimless movements, fidgeting of the hands), impulsive talking, and seeming disorientation to the environment. Children with the predominantly inattentive type may have no physical symptoms.

The medical evaluation focuses on identifying potentially treatable medical conditions that may contribute to or worsen the symptoms and signs. The evaluation should include a history of prenatal exposure (e.g., illicit substances, alcohol, tobacco), perinatal complications or infections, central nervous system infections, traumatic brain injury, cardiac disease, sleep-disordered breathing, poor appetite and/or picky eating, and a family history of ADHD.

Developmental assessment focuses on identifying the onset and progression of symptoms and signs. Assessment includes testing for developmental milestones, particularly language, and the use of ADHD-specific rating scales (e.g., Vanderbilt Assessment Scale , Conners Comprehensive Behavior Rating Scale, ADHD Rating Scale-5) ( 2 ). Versions of these scales are available for both family and school personnel, allowing assessment to be conducted in a variety of settings, as required by the Diagnostic and Statistical Manual of Mental Disorders (DSM-5-TR) criteria. Note that scales alone are not sufficient to make a diagnosis.

An educational assessment is aimed at documenting key symptoms and signs and may include review of educational records and use of psychological rating scales or tests. However, rating scales and tests alone often cannot distinguish ADHD from other developmental or behavioral disorders.

Reference materials on diagnostics

1. 1. Wolraich ML, Hagan JF Jr, Allan C, et al : Clinical Practice Guideline for the Diagnosis, Evaluation, and Treatment of Attention-Deficit/Hyperactivity Disorder in Children and Adolescents [published correction appears in Pediatrics 2020 Mar;145(3) :].  Pediatrics 144(4):e20192528, 2019. doi:10.1542/peds.2019-2528
2. 2. Izzo VA, Donati MA, Novello F, Maschietto D, Primi C : The Conners 3-short forms: Evaluating the adequacy of brief versions to assess ADHD symptoms and related problems.  Clin Child Psychol Psychiatry 24(4):791–808, 2019. doi:10.1177/1359104519846602

Treatment of ADHD

• Behavioural therapy
• Drug therapy, usually using stimulants such as methylphenidate or dextroamphetamine (both rapid-release and extended-release preparations)

Treatment recommendations for children with ADHD vary by age ( 1 ):

• Preschool-aged children: Initial treatment is behavioral therapy. If the response to behavioral interventions is inadequate or if symptoms are moderate to severe (e.g., impulsive flight, aggressive outbursts, other behaviors that put the child or others at risk of injury), medication may be considered.
• School-age children: Initial treatment is behavioral therapy combined with medication.

Randomized trials show that in school-aged children, behavioral therapy alone is less effective than therapy with stimulant medication, while the combination is better ( 2 , 3 , 4 ). There is also evidence to support the effectiveness of methylphenidate in preschool-aged children who do not respond to behavioral therapy alone, although the overall benefit appears to be less than in school-aged children ( 5 ). Although drug therapy does not correct the underlying neurophysiological differences in patients with ADHD, medications are effective in relieving ADHD symptoms and allowing patients to engage in activities previously inaccessible to them due to poor attention and impulsivity. Drug treatment often improves behavioral symptoms, improves the effects of behavioral therapy and academic performance, and increases motivation and self-esteem.

Treatment for ADHD in adults follows similar principles, but as in children, medication selection and dosage must be individualized based on benefits, side effects, and other medical conditions ( 2 ).

Stimulant drugs

The most widely used stimulant medications include methylphenidate or amphetamine salts. Response varies widely, and the dosage depends on the severity of the disorder and the child’s ability to tolerate the drug. Dosage is adjusted in frequency and amount until an optimal balance between response and side effects is achieved.

For children, methylphenidate is usually started at the lowest dose orally once daily (immediate-release form) and increased in frequency weekly, usually to about 2–3 times daily or every 4 hours during waking hours; many physicians try to schedule dosing in the morning and afternoon. If the response to therapy is inadequate but the drug is well tolerated by the patient, the dose may be increased. The goal is to find the optimal balance between benefit and side effects for each patient. Doses that are too low and do not provide adequate benefit may cause families to abandon treatment early, while doses that are too high may cause serious side effects with or without adequate clinical benefit. The dextrorotatory isomer of methylphenidate is the active moiety and is prescribed at half the dose.

Typically, dextroamphetamine (immediate-release form) is given orally once daily (often in combination with racemic amphetamine), then increased to 2–3 times daily or every 4 hours while awake. Titration of dose should help balance efficacy and side effects; actual doses vary considerably among individuals, but generally higher doses increase the likelihood of unwanted side effects. In general, dextroamphetamine is used at doses two-thirds those of methylphenidate .

Once the optimal dosage for methylphenidate or dextroamphetamine has been reached, equivalent doses of the same drug are switched to sustained-release forms to avoid the need for school administration. Extended-release preparations include wax matrix tablets with sustained release, biphasic capsules containing the equivalent of 2 doses, osmotic-release tablets, and transdermal patches that provide action for up to 12 hours. Both short- and long-acting liquid preparations are also available. Pure dextro preparations (eg, dextroamphetamine) are often used to minimize side effects such as anxiety; doses are typically half those of the mixed preparations. Prodrugs are also sometimes used because of their smoother release, longer duration of action, fewer side effects, and lower abuse potential. Learning is often improved with low doses, but behavioral improvement often requires higher doses.

Stimulant dosing schedules may be adjusted to cover specific days and time periods (e.g., school hours, homework time). Medication holidays may be scheduled on weekends, holidays, or during school vacations. Periodic placebo dosing (over 5–10 school days to smooth out day-to-day variability) is recommended to determine whether medication is still needed.

Common side effects of stimulants include:

• Sleep disorders (eg, insomnia)
• Headache
• Stomach pain
• Appetite suppression
• Increased heart rate and blood pressure

Depression is a less common side effect and can often present as an inability to shift focus easily (hyperfocus). This may present as a “disconnected” behavior (sometimes described by families as zombie-like behavior) rather than clinical childhood depression . In clinical practice, stimulant medications are sometimes used as an adjunctive treatment for depression. The “disconnected” behavior can sometimes be reversed by reducing the dose of the stimulant medication or using a different medication. People with anxiety disorders may also experience an exacerbation of anxiety symptoms.

Studies have shown that height growth slows within 2 years of taking stimulant drugs, and with continued use of stimulants, adult height potential may be reduced ( 6 ).

Non-stimulant drugs

Atomoxetine, a selective norepinephrine reuptake inhibitor, is also used . The drug is effective, but the data are mixed when considering its effectiveness compared with stimulant drugs ( 7 ). Some children experience nausea, sedation, irritability, temper tantrums, and, less commonly, liver toxicity and suicidal ideation. The initial dose is adjusted weekly. The long half-life allows once-daily dosing, but requires continuous use to maintain effectiveness.

Antidepressants of the selective norepinephrine reuptake inhibitor class such as bupropion and venlafaxine, alpha-2 agonists such as clonidine and guanfacine, and other psychoactive drugs are sometimes used when stimulants are ineffective or cause unacceptable side effects, but they are less effective and are not recommended as first-line treatment. These drugs are sometimes used in combination with stimulants to achieve a synergistic effect; careful monitoring for side effects is important.

Adverse drug interactions are a concern in the treatment of ADHD. Drugs that inhibit the metabolic enzyme CYP2D6, including some selective serotonin reuptake inhibitors (SSRIs) that are sometimes used in patients with ADHD, may potentiate the effects of stimulant medications. Analysis of potential drug interactions is an important part of pharmacologic management of patients with ADHD.

Behavior management

Psychological counseling, including cognitive behavioral therapy (e.g., goal setting, self-monitoring, modeling, role-playing), is often effective in helping children with ADHD socialize and cope. Structure and procedures are important.

Classroom behavior often improves with control of ambient noise and visual stimulation, appropriate task length, novelty, tutoring, and teacher proximity.

If you are having difficulty at home, you should seek additional professional help and training in behavioral management techniques. Adding incentives and rewards enhances behavioral management and is often effective. Children with ADHD, where hyperactivity and poor impulse control are prevalent, can often be helped at home by establishing structure that is consistent with parenting techniques and clear limits.

Elimination diets, megavitamin treatments, use of antioxidants or other compounds, nutritional and biochemical interventions had the least consistent effects. Biofeedback may be helpful in some cases, but is not recommended for routine use because there is no evidence of sustained effect.

Prognosis for ADHD

Traditional classrooms and educational activities often exacerbate symptoms and signs in children with untreated or inadequately treated ADHD. Specific pharmacological and educational interventions may be ongoing. Poor peer acceptance and loneliness increase with age and are associated with an apparent increase in symptoms. If ADHD is not diagnosed and adequately treated in a timely manner, many adolescents and adults with ADHD may subsequently develop substance abuse and alcoholism due to self-medication with medications (e.g., caffeine ) and illicit drugs (e.g., cocaine , amphetamines).

Although symptoms and signs of hyperactivity typically decrease with age, residual difficulties may be present in adolescents and adults. Predictors of poor outcomes in adolescents and adults include:

• Low intelligence
• Aggressiveness
• Social and interpersonal problems
• Mental or behavioral disorders in parents.

Problems in adolescence and adulthood manifest themselves primarily in the form of poor academic performance, low self-esteem, and difficulty learning appropriate social behavior. Adolescents and adults who have predominantly impulsive ADHD may have an increased incidence of personality and social behavior disorders, and many continue to display impulsivity, anxiety, and poor social skills. People with ADHD are likely to be more predisposed to work than to school or home life, especially if they can find work that does not require close attention.

Basic Provisions

• ADHD is characterized by inattention, hyperactivity/impulsivity, or a combination of both; it usually appears before age 12, including in preschoolers.
• The cause is unknown, but numerous putative risk factors have been identified.
• Diagnosis is made using clinical criteria, and care should be taken to identify other disorders (eg, autism spectrum disorders, certain learning or behavioral disorders, anxiety, depression) and adverse childhood experiences that may initially present similarly.
• Symptoms usually decrease with age, but some problems may persist in adolescents and adults.
• Treatment typically involves stimulant medications and cognitive behavioral therapy; in preschool-aged children, behavioral therapy alone is used.