From the Guidelines
The pathophysiology of ADHD is characterized by a complex interplay of genetic, neurochemical, and environmental factors, leading to executive deficits in cognitive domains such as visuospatial and verbal working memory, inhibitory control, vigilance, planning, and reward regulation. This is supported by extensive research efforts, including studies on the heritability of ADHD, which suggest a high heritability with a complex multifactorial etiology 1. Patients with ADHD show abnormal findings from structural and functional brain imaging studies, predominantly in larger-scale brain networks such as frontostriatal, frontoparietal, and ventral attention networks 1.
The core symptoms of ADHD are frequently associated with additional symptoms, such as sleep problems, depressed mood, or oppositional behavior, which further reduce psychosocial functioning 1. The diagnostic process is challenging and relies mainly on a careful and comprehensive clinical interview and behavioral observation of the patient and respective family members/caregivers, as well as an observation of their interactions.
Key aspects of ADHD pathophysiology include:
- Executive deficits in several cognitive domains, including visuospatial and verbal working memory, inhibitory control, vigilance, planning, and reward regulation 1
- Abnormalities in brain structure and function, particularly in the prefrontal cortex and its connections to other brain regions, such as the striatum and cerebellum 1
- Neurotransmitter imbalances, including dopamine and norepinephrine, which are critical for focus, motivation, and cognitive control 1
- High heritability, with multiple genes affecting neurotransmitter regulation, neuronal development, and synaptic functioning 1
- Environmental factors, such as prenatal exposure to toxins, premature birth, and early adversity, which can contribute to ADHD development by affecting neural systems during critical developmental periods 1
Overall, the pathophysiology of ADHD is complex and multifaceted, involving genetic, neurochemical, and environmental factors that contribute to the development of executive deficits and other core symptoms of the disorder. Current clinical guidelines recommend an individualized multimodal and multidisciplinary treatment approach, taking into account the age, severity of symptoms, and individual needs of the patient 1.
From the FDA Drug Label
The FDA drug label does not answer the question.
From the Research
Pathophysiology of ADHD
The pathophysiology of Attention-Deficit Hyperactivity Disorder (ADHD) is complex and not fully understood. However, research suggests that it is associated with impaired function and increased risk of poor outcomes in individuals with the condition 2.
- Neurochemical Basis: The use of medications such as methylphenidate, amphetamine, and atomoxetine to treat ADHD indicates a dopamine/norepinephrine deficit as the neurochemical basis of the disorder 3.
- Brain Structure and Function: Studies have shown that individuals with ADHD have a smaller volume of the total brain and various regions, including the prefrontal cortex, the caudate nucleus, and the vermis of the cerebellum 4.
- Frontostriatal Networks: Functional MRI has documented a specific deficit of frontostriatal networks in ADHD, which may contribute to the symptoms of the disorder 4.
- Genetic Factors: Molecular genetic studies have identified a number of candidate genes that have a small effect on behavioral variation in ADHD, and genome-wide significant linkage has been identified on chromosome 16 4.
- Environmental Factors: The interaction of genetic and environmental factors is thought to play a role in the development of ADHD, and integrative aetiological models are needed to take this interaction into account 4.
Clinical Presentation and Course
ADHD is a heterogeneous disorder with a complex clinical presentation and course.
- Co-morbidities: ADHD is often associated with co-morbidities, such as other mental health disorders, which can impact psychosocial functioning and treatment outcomes 3, 4.
- Gender Effects: There are gender effects in the presentation and course of ADHD, with males being more likely to be diagnosed with the disorder than females 4.
- Course and Outcome: The course and outcome of ADHD can vary widely, with some individuals experiencing persistent symptoms into adulthood and others experiencing remission 5, 4.