From the Guidelines
Attention Deficit Hyperactivity Disorder (ADHD) is a complex neurodevelopmental disorder caused by a combination of genetic, environmental, and neurochemical factors [ 1 ].
Key Factors
- The exact etiology is multifactorial, involving alterations in dopamine and norepinephrine neurotransmission [ 1 ].
- Abnormalities in brain structure and function, particularly in larger-scale brain networks such as frontostriatal, frontoparietal and ventral attention networks, have also been implicated in the pathophysiology of ADHD [ 1 ].
Symptoms and Diagnosis
- Symptoms of ADHD typically manifest in childhood and persist into adulthood, with an estimated prevalence of 2.5% in adults [ 1 ].
- Executive deficits in several cognitive domains, e.g., visuospatial and verbal working memory, inhibitory control, vigilance, planning and reward regulation, are common in patients with ADHD [ 1 ].
- Diagnosis is challenging and relies mainly on a careful and comprehensive clinical interview and behavioral observation of the patient and respective family members/caregivers [ 1 ].
Treatment
- Current clinical guidelines recommend an individualized multimodal and multidisciplinary treatment approach, including pharmacological and/or non-pharmacological interventions [ 1 ].
- Timely and adequate treatment is crucial to prevent negative effects on long-term outcomes, such as academic achievement, employment status, and traffic accidents [ 1 ].
From the Research
Causes of Attention Deficit Hyperactivity Disorder (ADHD)
The exact etiology of ADHD is not fully understood, but it is considered a multifactorial and heterogeneous disorder with several contributing factors. Some of the possible causes of ADHD include:
- Genetic variations: Studies have shown that genetic variations can influence brain changes in patients with ADHD 2, 3, 4, 5.
- Neurodevelopmental issues: ADHD is characterized by developmentally abnormal brain networks related to cognition, attention, emotion, and sensorimotor functions 2, 4.
- Brain injuries: Severe brain injuries may contribute to the development of ADHD 2.
- Neuroinflammation: Neuroinflammation has been linked to the development of ADHD 2.
- Environmental toxins: Exposure to environmental toxins, such as heavy metals and organohalide pollutants, may contribute to the development of ADHD 2, 6.
- Premature birth: Premature birth has been linked to an increased risk of developing ADHD 2.
- Consanguineous marriages: Consanguineous marriages may increase the risk of developing ADHD due to genetic factors 2.
- Food additives and intolerances: Adverse responses to food additives and intolerances to foods may contribute to the development of ADHD 6.
- Sensitivities to environmental chemicals: Sensitivities to environmental chemicals, molds, and fungi may also contribute to the development of ADHD 6.
Biological Mechanisms of ADHD
The biological mechanisms of ADHD are complex and involve multiple systems, including:
- Dopaminergic pathways: Alterations in dopaminergic pathways have been linked to ADHD 3, 4, 6.
- Neurotransmission: Dysfunctions in catecholamine-regulated neurotransmission, especially dysfunction of dopamine transporters, have been observed in ADHD 3.
- Brain structure and function: Volumetric reductions and decreased neural activities in the frontal lobe, basal ganglia, limbic system, and cerebellum have been observed in ADHD 3.
- Executive function and reward system: Impairment of executive function and the reward system, referred to as the dual pathway model, has been proposed as a biological change underlying ADHD 3.
- Default mode network: Dysfunction of the default mode network has also been linked to ADHD 3.