Attention Deficit Hyperactivity Disorder (ADHD)

ADHD is a neurodevelopmental disorder that generally emerges in early childhood.  ADHD is characterized by inattention, hyperactivity and impulsivity, and can interfere with academic, social and economic functioning as well as other areas of development. ADHD can be treated and managed in primary care pediatrics.

Epidemiology, Risk Factors, & Pathophysiology

The overall prevalence of ADHD is estimated at 3.4-7%.  Males are identified with ADHD more commonly than are females at a rate of 3:1 or greater; this may reflect more referral bias than prevalence (Rucklidge 2016).

The developmental trajectories of ADHD are variable -while about 65% continue to meet full criteria or have only achieved partial remission by adulthood, some experience full remission.

Risk Factors

  • Genetics:  The relative risk in first degree relatives of probands with ADHD is 5-9, and twin studies indicate heritability of about 76%, similar to autism and schizophrenia.  Certain genetic syndromes, including Fragile X, Williams syndrome, and 22p deletion syndrome are associated with hyperactivity and inattention symptoms. 
  • Non-genetic risk factors for ADHD include prematurity, low birth weight, prenatal exposure to maternal cigarette smoking, alcohol, and drugs of abuse.  In utero or early childhood exposure to environmental toxins such as lead and organophosphate pesticides is associated with increased risk. 

Pathophysiology

Studies have posited both hypoactive and hyperactive catecholamine (dopamine and norepinephrine) release hypotheses as the etiology of ADHD.

Comorbidity & Differential Diagnosis

ADHD commonly co-occurs with tics and Tourette’s Disorder, Oppositional Defiant Disorder, Obsessive Compulsive Disorder, anxiety disorders, and depression.  Young people with ADHD are at higher risk than their peers for development of substance use disorders.

The following categories of conditions may cause inattention and/or hyperactivity and be confused with ADHD, but they may also co-occur with ADHD.

  • Sensory:  vision or hearing problems, sensory sensitivities
  • Medical: hyperthyroidism, pruritic skin conditions, absence seizures, others
  • Sleep: obstructive sleep apnea, poor sleep hygiene, narcolepsy
  • Learning disorders: it is difficult to focus when you don't understand the content
  • Trauma: traumatic memories and heightened threat perception may present as inattention or agitation
  • Social: bullying, isolation, fear
  • Anxiety: internal preoccupation interferes with attention
  • Mood: depression, mania

Prognosis

A diagnosis of ADHD is associated with low academic attainment and early leaving of formal education.  ADHD also predicts antisocial behavior, accidental injury, and substance misuse in adolescence.  In the longer term, childhood ADHD is associated with poor occupational, economic and social outcomes and higher risk of substance use disorders, psychiatric hospital admissions, incarceration and mortality.   

Symptoms

DSM-5 Criteria

Five or more symptoms of inattention and/or ≥5 symptoms of hyperactivity/impulsivity must have persisted for ≥6 months to a degree that is inconsistent with the developmental level and negatively impacts social and academic/occupational activities.

Inattentive symptoms:

  • Makes careless mistakes/lacks attention to detail
  • Difficulty sustaining attention
  • Does not seem to listen when spoken to directly
  • Fails to follow through on tasks and instructions
  • Exhibits poor organization
  • Avoids/dislikes tasks requiring sustained mental effort
  • Loses things necessary for tasks/activities
  • Easily distracted (including unrelated thoughts)
  • Is forgetful in daily activities

Hyperactivity/impulsivity symptoms:

  • Fidgets with or taps hands or feet, squirms in seat
  • Leaves seat in situations when remaining seated is expected
  • Experiences feelings of restlessness
  • Has difficulty engaging in quiet, leisurely activities
  • Is “on-the-go” or acts as if “driven by a motor”
  • Talks excessively
  • Blurts out answers
  • Has difficulty waiting their turn
  • Interrupts or intrudes on others

Several symptoms (inattentive or hyperactive/impulsive) were present before the age of 12 years.

Several symptoms (inattentive or hyperactive/impulsive) must be present in ≥2 settings (eg, at home, school, or work; with friends or relatives; in other activities).

There is clear evidence that the symptoms interfere with or reduce the quality of social, academic, or occupational functioning.

Symptoms do not occur exclusively during the course of schizophrenia or another psychotic disorder, and are not better explained by another mental disorder (eg, mood disorder, anxiety disorder, dissociative disorder, personality disorder, substance intoxication, or withdrawal).

Mild: Few, if any, symptoms in excess of those required to make the diagnosis are present, and symptoms result in no more than minor impairments in social or occupational functioning.

Moderate: Symptoms or functional impairment between “mild” and “severe” are present.

Severe: Many symptoms in excess of those required to make the diagnosis, or several symptoms that are particularly severe, are present, or the symptoms result in marked impairment in social or occupational functioning.

Previously called “subtypes”, the term “presentations” reflects the patient’s current symptom profile which may change over time.

The named presentation is used when symptoms of either inattention, hyperactivity, or both have been present for at least 6 months.

ADHD, Combined presentation

ADHD, Predominantly Inattentive presentation

ADHD, Predominantly Hyperactive/Impulsive presentation

American Psychiatric Association. (2013). Diagnostic and statistical manual of mental disorders (5th ed.). Washington, DC

Screening and Rating Scales

Validated rating scales are a key component of diagnosis of ADHD and of monitoring response to treatment. As ADHD symptoms need to be identified in two or more settings, teacher measures are particularly valuable to collect. 

Several public domain ADHD rating scales are available. They differ in the number of questions, the age range for which they have been validated, and the reporter (parent, teacher, youth). 

Workup

  • History (family history, child’s symptom history, child’s academic history, child’s medical history)
  • Rating scales
  • Rule out other causes of inattention/hyperactivity
  • There is no evidence that neurological testing or imaging contributes to diagnosis.

Psychotherapy Treatments

Parent Management Training has been promoted as first line treatment for preschool aged children with ADHD.  Evidence for efficacy of Parent Management Training in improving core symptoms of ADHD is lacking, but it may improve parenting skills and decrease parental stress. (Cochrane Review 2011)

Pharmacologic Treatments

Pharmacotherapy with stimulant medications is first-line treatment for ADHD.  

Stimulants are highly effective in most patients and are generally well tolerated although decreased appetite and weight loss or failure to gain weight may preclude use in some patients.  Younger children are more likely to have emotional side effects (irritability) than are older children.

Non-stimulant medications are a second line treatment option that may be used as monotherapy or adjunctive to stimulants.  

We cover ADHD pharmacologic management in the following modules:

Adjunctive, Complementary & Alternative Treatments

Adjunctive Treatment

Regular physical exercise may improve ADHD symptoms in children and adolescents also treated with pharmacotherapy (Neudecker et al., 2019).

Complementary and alternative treatments

There is a long history of dietary modifications thought to improve ADHD symptoms but little support for elimination diets in most children.  

Supplementation of Vitamin D, iron and zinc in children deficient in these nutrients is advised. 

The Course of Treatment in Pediatrics

Children with marked hyperactivity and impulsivity are likely to present at a younger age than do those with a predominately inattentive ADHD presentation.  

Preschool and early school aged children may respond less well to an initial stimulant and may have more side effects including irritability and emotional sensitivity.

These children may respond well to the same medication in a year or 2.

Children with ADHD may take stimulant and/or non-stimulant medications indefinitely.  Height and weight must be monitored (see side effects above).

Some families prefer to not give stimulant medications on weekends or summer holidays.  This does not diminish stimulant effectiveness in most children.  We encourage parents to give stimulant medications when the child is at home often enough that they know how the child looks and feels when taking it, and if social interactions in the home are better when the child takes the medication.

At some point, many older children want a trial off their stimulant medication.  Such a trial should include a plan to assess symptoms and functional impairment off medication.  

Some children will do well for years on the same medication, adjusting the dose for growth.  Others will do well for a period and then not gain any benefit from a dose increase.  The next step is to switch to a different stimulant.  See the ADHD treatment algorithm.

Resources

For patients and families:

CHADD.org (Children and Adults with Attention-Deficit Hyperactivity Disorder)

ADHD Parents's Medication Guide (American Academy of Child and Adolescent Psychiatry)

ADHD Resource Center (American Academy of Child and Adolescent Psychiatry)

ADHD Booklet for Parents (American Academy of Pediatrics)

For providers:

NICHQ ADHD Toolkit

ADHD: Pediatric Mental Health Minute Series

References

Clinical Practice Guideline for the Diagnosis, Evaluation, and Treatment of Attention-Deficit/Hyperactivity Disorder in Children and Adolescents. (pdf) Wolraich ML, Hagan JF Jr, Allan C, Chan E, Davison D, Earls M, Evans SW, Flinn SK, Froehlich T, Frost J, Holbrook JR, Lehmann CU, Lessin HR, Okechukwu K, Pierce KL, Winner JD, Zurhellen W; SUBCOMMITTEE ON CHILDREN AND ADOLESCENTS WITH ATTENTION-DEFICIT/HYPERACTIVE DISORDER. Pediatrics. 2019 Oct;144(4):e20192528

Caye A, Swanson JM, Coghill D, Rohde LA. Treatment strategies for ADHD: an evidence-based guide to select optimal treatment. Molecular psychiatry. 2019;24(3):390-408.

Kieling R, Rohde LA. ADHD in children and adults: diagnosis and prognosis. Current topics in behavioral neurosciences. 2012;9:1-16.

Neudecker, C., Mewes, N., Reimers, A. K., & Woll, A. (2019). Exercise Interventions in Children and Adolescents With ADHD: A Systematic Review. Journal of Attention Disorders, 23(4), 307–324. 

O'Neill S, Rajendran K, Mahbubani SM, Halperin JM. Preschool Predictors of ADHD Symptoms and Impairment During Childhood and Adolescence. Current psychiatry reports. 2017;19(12):95.

Rucklidge JJ. Gender differences in attention-deficit/hyperactivity disorder. The Psychiatric clinics of North America. 2010;33(2):357-373.

Sharma A, Couture J. A review of the pathophysiology, etiology, and treatment of attention-deficit hyperactivity disorder (ADHD). The Annals of pharmacotherapy. 2014;48(2):209-225.