ATTENTION-DEFICIT/HYPERACTIVITY DISORDER
Diagnosis, course, and prevalence It is estimated that ADHD affects 3% to 7% of school-aged children and is the most common neurobehavioral disorder of childhood. ADHD is diagnosed more often in boys (8% to 9%) than girls (3% to 4%), but the exact male-to-female ratio is debated (Hinshaw, 2018). ADHD is diagnosed more often in children from lower income families, and there are differences in diagnostic rates by race and ethnicity, with non- Hispanic Black children often having the highest diagnostic rates (Shi et al., 2021; Zablotsky & Alford, 2020). ADHD is typically diagnosed during early elementary school years, when impairment in academic functioning becomes evident. However, excessive motor behavior and early symptoms may be evident in the toddler years (APA, 2013). In the DSM-5 , there are three specifiers for ADHD, namely predominantly inattentive presentation, predominantly hyperactive/impulsive presentation, and combined presentation in which features of both inattention and hyperactivity are present to a significant degree. Specifiers also indicate whether the disorder is in partial remission, as well as the severity of the disorder as either mild, moderate, or severe. The diagnosis of “other specified” attention-deficit/hyperactivity disorder may be used when persons have symptoms of ADHD that cause significant distress Etiology of attention-deficit/hyperactivity disorder Genetics play a strong role in the etiology of ADHD. A parent with ADHD has a 35% to 54% chance of having a child with ADHD (Barkley, 2016). As many as 25 to 44 genes may be involved in causing ADHD. Environmental contributions also are important, accounting for the remaining variance of ADHD Neurobiology of attention-deficit/hyperactivity disorder ADHD is categorized as a neurodevelopmental disorder because neurologic abnormalities are present early in life that have pervasive effects on behavior (Barkley, 2016). The brain regions most often implicated in the pathophysiology of ADHD are the prefrontal cortex, anterior cingulate cortex, frontal aspect of the corpus callosum, basal ganglia, and cerebellum (Barkley, 2016). Most of these neural regions are part of frontal lobe circuits that connect with subcortical regions. As described previously, this frontal lobe circuitry is associated with executive functions, such as inhibition, self-regulation, emotional regulation and expression, planning, judgment, and sustained attention (José et al., 2020). The symptoms and behaviors of ADHD have been
or impairment but do not meet the full criteria for ADHD or another neurodevelopmental disorder. Children who often fidget with their hands or feet, have difficulty waiting turns, and run about or climb excessively in inappropriate situations are displaying hyperactive symptoms. Examples of inattentive symptoms are frequently not seeming to listen when spoken to directly and losing things necessary for tasks or activities. Diagnostic guidelines for ADHD in DSM‑5 require evidence of certain numbers of hyperactive and/or inattention symptoms, with some symptoms appearing before age 12, and the symptoms must be associated with functional impairment (APA, 2013). A systematic empirical review of 97 studies indicated that the predominantly inattentive type is most common, but the combined type is most likely to be referred for clinical services (Willcutt, 2012). For a substantial majority of people with ADHD, symptoms persist into adulthood (Adler et al., 2017). Many children with ADHD have a comorbid disorder, including conduct disorder, oppositional defiant disorder, anxiety disorder, depressive disorder, or a specific learning disorder (APA, 2013; Hinshaw, 2018). Early and accurate diagnosis and treatment are critical to promote the highest level of social and academic functioning possible and potentially protect against the development of some of these comorbid disorders. symptoms. These environmental contributions to ADHD include poor nutrition, birth complications (e.g., premature birth, low birth weight), parental smoking, and exposure to toxins (e.g., lead poisoning) (Barkley, 2016). observed to share many features with frontal lobe injuries, such as deficits in sustained attention, inhibition, self-regulation, and behavioral organization (Barkley, 2016). The brains of persons with ADHD have 3% to 10% less gray matter volume than the brains of persons without ADHD (Barkley 2016). The frontal regions discussed above can be 15% to 30% smaller than those in normal-for-their-age peers. In general, the prefrontal cortex also is hypoactive, or underactive, in persons with ADHD as compared to controls. Right hemisphere structures are affected more than left hemisphere structures (Barkley, 2016). Ironically, attention is rarely impaired in ADHD. In fact, calling the disorder an “attention deficit” disorder is unfortunate because it is misleading about the neuropsychology of the disorder. In some contexts, attention can be very strong and focused in persons with ADHD. Rather than deficient attention, it is more common for persons with ADHD to have variable attention (Barkley, 2016). Attention can be quite good in some contexts; just ask parents of some children with ADHD. These parents will tell you that their child can be highly focused on preferred activities, such as a favorite video game or book. The child can get completely absorbed in some tasks and, in fact, it may be hard to draw their attention away from tasks in which they are engrossed. But at other times, persons with ADHD may have significant trouble controlling and directing their attention. This variability can be evident during the course of a neuropsychological evaluation. The core neuropsychological impairment in ADHD appears to be in the domain of executive function and not in attention. People with ADHD can have trouble with inhibition or stopping their behavior long enough to think through the consequences of their actions. They may be impulsive and disinhibited, often acting without thinking (Barkley, 2016). It is these
Assessment and diagnosis of attention-deficit/hyperactivity disorder Contrary to popular belief, ADHD is not a neuropsychological diagnosis. That is, diagnosis is not based on neuropsychological data. Rather, ADHD is a behavioral disorder and is based on the presence or absence of behavioral features that are listed in the DSM-5 , such as “is often easily distracted by extraneous stimuli, often has difficulty organizing tasks and activities, and often talks excessively” (APA, 2013, pp. 59-60). Assessment of ADHD requires input from parents, teachers, and other caregivers to get a thorough history of the presenting symptoms, as well as associated functional impairment. Behavior ratings scales and behavioral observations, during testing or in the classroom, are part of the assessment.
Neuropsychological testing for ADHD referrals is important, not so much for diagnostic purposes but to document cognitive and emotional strengths and weaknesses of a particular patient and to assess for a specific learning disorder. A specific learning disorder is often comorbid with ADHD, and sometimes ADHD can be mistaken for a specific learning disorder, and vice versa. Although not needed in all cases, assessment of IQ, academic achievement, attention, learning and memory, language, executive functions, and visuospatial skills can be useful in an ADHD assessment.
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