Definition

Attention-Deficit/Hyperactivity Disorder (ADHD) is a neurodevelopmental disorder characterized by persistent patterns of inattention, hyperactivity, and impulsivity that interfere with functioning or development.

History

  • Early Descriptions (18th–19th Century):

    • Sir Alexander Crichton (1798) described “mental restlessness” in children.
    • George Still (1902) presented lectures on “defective moral control,” now considered early ADHD descriptions.

  • Mid-20th Century:

    • 1937: Dr. Charles Bradley discovered that Benzedrine (an amphetamine) improved behavior in children with behavioral problems.
    • 1950s–1960s: The term “hyperkinetic impulse disorder” was used, focusing on hyperactivity.

  • DSM Evolution:

    • 1980 (DSM-III): “Attention Deficit Disorder” (ADD) introduced, separating attention issues from hyperactivity.
    • 1987 (DSM-III-R): “ADHD” became the standard term, recognizing subtypes (inattentive, hyperactive-impulsive, combined).

Key Experiments

  • Bradley’s Benzedrine Experiment (1937):

    • Children with behavioral issues given Benzedrine showed improved focus and reduced hyperactivity, leading to stimulant use in ADHD treatment.

  • Twin Studies (1990s–present):

    • Identical twins show higher concordance rates for ADHD than fraternal twins, supporting a strong genetic component.

  • Neuroimaging Studies:

    • MRI scans reveal structural differences in the prefrontal cortex, basal ganglia, and cerebellum in individuals with ADHD.
    • Functional MRI (fMRI) shows altered connectivity in attention networks.

  • Executive Function Testing:

    • Continuous Performance Test (CPT) and Stroop Test used to assess attention, impulsivity, and cognitive control in ADHD subjects.

Modern Applications

  • Diagnosis:

    • Multi-method assessment: clinical interviews, parent/teacher questionnaires, neuropsychological tests.
    • DSM-5 criteria: Symptoms must be present before age 12, occur in two or more settings, and cause significant impairment.

  • Treatment:

    • Pharmacological: Stimulants (e.g., methylphenidate, amphetamines), non-stimulants (e.g., atomoxetine).
    • Behavioral Therapy: Cognitive-behavioral therapy (CBT), parent training, classroom interventions.
    • Digital Therapeutics: FDA-approved apps (e.g., EndeavorRx) use video games to improve attention.

  • Educational Support:

    • Individualized Education Programs (IEPs), 504 plans, classroom accommodations (extra time, movement breaks).

  • Genetic Research:

    • Genome-wide association studies (GWAS) identify risk loci (e.g., DRD4, DAT1 genes).
    • Polygenic risk scores increasingly used for research, not clinical diagnosis.

Controversies

  • Overdiagnosis vs. Underdiagnosis:

    • Concerns about ADHD being overdiagnosed in some populations, while underdiagnosed in others, especially girls and minority groups.

  • Medication Use:

    • Debate over long-term effects and safety of stimulant medications.
    • Non-medical use of stimulants by students for cognitive enhancement raises ethical issues.

  • Societal Factors:

    • Impact of changing educational environments, screen time, and social expectations on ADHD prevalence and diagnosis.

  • Diagnostic Criteria:

    • Criticism that current criteria may pathologize normal childhood behaviors.
    • Cultural differences in symptom interpretation.

Relation to Current Events

  • COVID-19 Pandemic:
    • Remote learning and increased screen time have highlighted attention difficulties in children, leading to a surge in ADHD evaluations.
    • Recent studies show increased ADHD symptom reporting during lockdowns (see: Cortese et al., 2021, European Child & Adolescent Psychiatry).

Surprising Aspect

The most surprising aspect of ADHD science is the role of environmental factors in symptom expression. While ADHD has a strong genetic basis, recent research shows that prenatal exposure to stress, pollution, and even maternal diet can influence symptom severity and onset. For example, a 2022 study published in JAMA Network Open found that children exposed to higher levels of air pollution during pregnancy had a significantly increased risk of developing ADHD symptoms.

Recent Research

  • Reference Study:
    • Faraone, S.V., Asherson, P., Banaschewski, T., et al. (2021). “Attention-deficit/hyperactivity disorder.” Nature Reviews Disease Primers, 7, 1.
      • This review highlights advances in genetic understanding, neuroimaging, and new digital therapeutic approaches.
      • Emphasizes the importance of early intervention and individualized treatment plans.

Summary

ADHD is a complex neurodevelopmental disorder with a rich history of scientific exploration. Key experiments have illuminated its genetic and neurological underpinnings, while modern applications focus on evidence-based diagnosis and treatment. Controversies persist regarding diagnosis, medication, and societal influences. Current events such as the COVID-19 pandemic have brought increased attention to ADHD symptoms and management. The interplay between genetic predisposition and environmental factors remains a surprising and active area of research. Recent studies continue to refine understanding and treatment, making ADHD science a dynamic and evolving field.

Citation

  • Faraone, S.V., et al. (2021). Attention-deficit/hyperactivity disorder. Nature Reviews Disease Primers, 7, 1.
  • Cortese, S., et al. (2021). Impact of COVID-19 on ADHD symptoms. European Child & Adolescent Psychiatry.
  • JAMA Network Open (2022). Prenatal air pollution exposure and ADHD risk.