Attention Deficit Hyperactivity Disorder

Clinical Presentation

Individuals with ADHD often exhibit poor sustained attention, difficulty concentrating on tasks, and are easily distracted, with problems shifting focus appropriately, as noted by the American Academy of Pediatrics 1
Difficulty suppressing inappropriate responses and impulsive behaviors and decision-making are common, according to the American Psychological Association 2
Challenges with organizing tasks and activities, poor time management, and difficulty completing multi-step tasks are also prevalent, as reported by the American Academy of Pediatrics 1
Abnormalities in larger-scale brain networks, such as frontostriatal, frontoparietal, and ventral attention networks, are associated with ADHD, as found by the National Institute of Mental Health 2
ADHD presents with inattentive symptoms, hyperactive-impulsive symptoms, or a combined presentation, according to the American Academy of Pediatrics 1
Adolescents with ADHD show less overt hyperactive behavior but continue to struggle with attention and executive function, as observed by the American Academy of Pediatrics 3
Adults with ADHD are more likely to present with predominantly inattentive symptoms, according to the American Academy of Pediatrics 1

ADHD is characterized by dysfunction in the prefrontal cortex and connected brain networks, with dysregulation of dopamine and norepinephrine neurotransmission as the central neurobiological mechanism, as per the American Psychiatric Association 2
Executive dysfunction arises from disruption to distributed neural networks, including frontostriatal circuits that connect prefrontal regions with basal ganglia, which are involved in executive functions 4
Executive functions can be divided into several distinct components, including working memory, inhibition, set shifting, cognitive flexibility, planning and organization, and self-monitoring, which are essential for goal-directed behavior and daily functioning 4

For patients with ADHD, pharmacological treatment with stimulants that target dopamine and norepinephrine systems is recommended, along with cognitive behavioral therapy and other non-pharmacological interventions, as suggested by the American Academy of Child and Adolescent Psychiatry 5, 6
Stimulants, such as methylphenidate and amphetamines, are first-line pharmacotherapy for ADHD due to their direct effects on dopamine and norepinephrine systems 2, 5, 6
Methylphenidate inhibits dopamine and norepinephrine transporters, acts as a serotonin type 1A receptor agonist, and increases synaptic dopamine in the striatum 5, 6
Amphetamines inhibit dopamine and norepinephrine transporters, inhibit vesicular monoamine transporter 2, and increase synaptic dopamine and norepinephrine 2
The National Institute of Mental Health recommends a multidisciplinary approach to treatment, including cognitive training, behavioral therapy, and medication management 7

Assessment of executive dysfunction requires a comprehensive approach, including bedside screening tools, such as the Frontal Assessment Battery (FAB) and the Institute of Cognitive Neurology Frontal Screening (IFS), as well as formal neuropsychological testing, such as letter verbal fluency and the Stroop Test 8
Functional assessment, including evaluation of impact on activities of daily living and collateral history from caregivers, is also essential 8
When both conditions coexist, treatment decisions should address the condition causing the greatest functional impairment to morbidity, mortality, and quality of life, and regular follow-up is essential to assess treatment efficacy and adjust management strategies as needed 8
Serial assessments are important to detect progressive executive dysfunction, which may suggest neurodegenerative disease, and treatment should be tailored to the individual's needs and circumstances 8
Executive dysfunction significantly impacts quality of life and functional independence, making early identification and targeted intervention crucial for optimal patient outcomes 8

Executive dysfunction is a feature of numerous conditions, including frontotemporal dementia, Alzheimer's disease, Parkinson's disease, Lewy body dementia, vascular cognitive impairment, and traumatic brain injury 8
Psychiatric disorders, such as obsessive-compulsive disorder, major depression, and bipolar disorder, also exhibit executive dysfunction 4
Approximately 46% of DRS patients have associated congenital abnormalities, and about 20% of DRS cases have absent binocular stereoacuity and 16.9% have amblyopia 1