ADHD

Introduction and Epidemiology

• Attention-deficit/hyperactivity disorder (ADHD) is one of the most common and extensively studied neurobehavioral disorders of childhood, characterized by symptoms of inattention, poor impulse control, decreased self-inhibitory capacity, and motor overactivity.
• The estimated prevalence of ADHD in India is 1.3 per 1000 children.
• Worldwide prevalence studies estimate that 5% to 10% of school-age children are affected by the disorder.
• The condition exhibits a strong male preponderance, with a male-to-female ratio of 4:1 for the predominantly hyperactive-impulsive presentation and 2:1 for the predominantly inattentive presentation.
• Females are more likely to be diagnosed with the inattentive presentation, which is frequently associated with internalizing symptoms such as anxiety and low mood.
• Children with below-average intelligence quotients (IQ) possess an increased risk of coexisting ADHD, though children with high IQ are just as likely to have ADHD as those with average IQ.

Etiology and Pathogenesis

• ADHD is a polygenic disorder where multiple common genetic variants act in tandem to increase the risk, demonstrating a 70% to 80% heritability in twin studies.
• First-degree relatives of individuals with ADHD have a 5- to 10-fold increased risk of developing the condition.
• Neuroanatomic studies reveal structural and functional abnormalities, most notably the dysregulation of frontal subcortical circuits and a median 3-year delay in the attainment of peak cortical thickness in the prefrontal regions of the brain.
• Abnormalities in the cerebellum, specifically involving the midline and vermian elements, are also commonly identified.
• The core biochemical pathophysiology involves an imbalance in brain catecholamine metabolism, specifically a decrease in inhibitory dopamine activity coupled with an increase in norepinephrine activity.
• Patients with ADHD have an increased dopamine transporter density, resulting in the overly rapid clearance of dopamine from the synapse.
• Environmental risk factors heavily influence pathogenesis; these include prenatal exposure to tobacco smoke or alcohol, prematurity (including late-preterm birth), and underlying maternal mental illness.
• Dietary factors are not considered a primary pathogenetic mechanism for most children, though a highly specific and small subset of patients may be uniquely sensitive to certain foods, sugars, or additives.

Clinical Manifestations

• Clinical presentations change dynamically with age and development.
• Preschool-aged children most commonly manifest motor restlessness, aggressive tendencies, and disruptive behaviors.
• Older adolescents and adults are more likely to present with disorganized, distractible, and inattentive symptoms, as overt motor hyperactivity generally decreases in late childhood.
• Symptoms of impulsivity and inattention frequently persist throughout the lifespan.
• The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) categorizes ADHD into three distinct presentations: predominantly inattentive, predominantly hyperactive-impulsive, and combined presentation.

Diagnostic Criteria (DSM-5)

• The diagnosis of ADHD is fundamentally clinical and heavily relies on the fulfillment of predefined criteria across inattention, hyperactivity, and impulsivity domains.

Diagnostic Approach and Evaluation

• The American Academy of Pediatrics recommends initiating an evaluation for ADHD in any child between 4 and 18 years of age who presents with academic or behavioral problems accompanied by symptoms of inattention, hyperactivity, or impulsivity.
• Information must be systematically gathered from multiple sources, including the child, parents, teachers, and other relevant caretakers.
• Validated behavior rating scales, such as the Vanderbilt ADHD Rating Scale, Conners 3 ADHD Index, and the ADHD Rating Scale 5, are essential for assessing symptom frequency and functional impairment across different settings.
• Broadband rating scales (e.g., Child Behavior Checklist [CBCL] or Behavioral Assessment Scale for Children [BASC]) are highly useful in screening for coexisting conditions.
• A comprehensive physical examination is required, with particular attention directed toward the neurologic and cardiac systems, thyroid evaluation, hearing/vision screening, and an assessment for dysmorphic features suggestive of genetic syndromes (e.g., fetal alcohol syndrome).
• Routine laboratory tests, computerized attentional tasks, quantitative electroencephalography, and brain imaging are not routinely recommended for ADHD diagnosis and are subject to high false-positive and false-negative rates.

Differential Diagnosis and Comorbidities

Management Strategies

• The cornerstone of management is a multimodal, chronic-care approach that includes behavioral therapy, school-based accommodations, and pharmacotherapy.
• For preschool-age children (under 6 years), evidence-based parent- and/or teacher-administered behavior therapy is the recommended first-line treatment, with medication reserved only for cases with moderate to severe functional impairment where behavioral interventions fail or are unavailable.
• For school-age children ($\ge$ 6 years) and adolescents, FDA-approved ADHD medications are considered the first-line treatment, strongly recommended to be used in conjunction with behavioral and educational interventions.

Behavioral and Educational Interventions

• Behavioral parent training (parent training in behavioral management) is a well-established intervention teaching caregivers to use positive reinforcement, tangible rewards, and systematic consequences to shape appropriate behavior.
• Educational bypass strategies and accommodations include preferential seating, frequent teacher check-ins, untimed tests, and the use of a daily report card to bridge home-school communication.
• For children failing to progress with general classroom accommodations, formal support via a 504 Plan or an Individualized Education Program (IEP) is mandated.

Pharmacotherapy

• Stimulants are the most commonly used medications and represent the most effective pharmacological intervention, demonstrating a standardized treatment effect size of approximately 1.0.
• Non-stimulant medications (norepinephrine reuptake inhibitors and alpha-2 adrenergic agonists) demonstrate a slightly lower effect size of approximately 0.7 but are valuable for patients with poor stimulant tolerability, coexisting tics, or a high risk of substance diversion.
• Before initiating stimulants, a targeted cardiac history should be taken to screen for cardiomyopathy, arrhythmias, or a family history of sudden cardiac death under 50 years of age.
  
• Routine monitoring of height, weight, pulse, and blood pressure is mandatory during pharmacotherapy.

Prognosis and Complications

• ADHD is a chronic condition extending into adulthood for a significant portion of patients; approximately one-third to two-thirds of children diagnosed will continue to manifest impairing symptoms into their adult lives.
• More than 50% of individuals with a childhood diagnosis of ADHD will develop a comorbid mental health condition, such as an anxiety disorder, depression, or substance use disorder in adulthood.
• Without proper treatment, adolescents and young adults face an increased likelihood of educational underachievement, occupational difficulties, relationship discord, and severe risk-taking behaviors.
• The disorder is associated with a significantly increased risk of morbidity and premature death due to motor vehicle accidents, substance abuse, criminality, and suicide.
• Consistent, multimodal treatment incorporating medication and adjuvant behavioral therapies significantly lowers the risk of these adverse life outcomes.