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INTRODUCTION — Attention deficit hyperactivity disorder (ADHD) is a disorder that manifests in childhood with symptoms of hyperactivity, impulsivity, and/or inattention. The symptoms affect cognitive, academic, behavioral, emotional, and social functioning (table 1) .
This topic review focuses on the clinical features and evaluation of ADHD. The epidemiology, pathogenesis, management, and prognosis of ADHD in children and adolescents and ADHD in adults are discussed separately.
Core symptoms — ADHD is a syndrome with three categories of symptoms: hyperactivity, impulsivity, and inattention (table 1). Each of the core symptoms of ADHD has its own pattern and course of development. The complaint regarding symptoms of ADHD may originate from the parents, teachers, or other caregivers .
Hyperactivity — Hyperactive behavior is identified through excessive fidgetiness or talking, difficulty remaining seated when required to do so, difficulty playing quietly, and frequent restlessness or seeming to be always "on the go" (table 1).
The hyperactive symptoms typically are observed by the time the child reaches four years of age and increase during the next three to four years [3,4]. They peak in severity when the child is seven to eight years of age, after which they begin to decline steadily. By the adolescent years, the hyperactive symptoms can be barely discernible to observers, but adolescents often report internal restlessness or inability to settle down.
Impulsivity — Impulsive behavior almost always occurs in conjunction with hyperactivity in young children. Impulsive behavior is manifested by difficulty waiting turns, blurting out answers too quickly, disruptive classroom behavior, intruding or interrupting other's activities, peer rejection, and unintentional injury (table 1).
Similar to the hyperactive symptoms, the impulsive symptoms typically are observed by the time the child reaches four years of age and increase during the next three to four years to peak in severity when the child is seven to eight years of age [3,4]. In contrast to hyperactive symptoms, impulsive symptoms usually remain a problem throughout the life of the individual. (See "Attention deficit hyperactivity disorder in children and adolescents: Overview of treatment and prognosis", section on 'Prognosis'.)
The focus of impulsivity is related to the environment. As an example, adolescents with ADHD who are untreated and in an environment where alcohol and other commonly abused substances are readily available are at greater risk of engaging in drug use or experimentation than are adolescents without ADHD .
Inattention — Inattention may take many forms, including forgetfulness, being easily distracted, losing or misplacing things, disorganization, academic underachievement, poor follow-through with assignments or tasks, poor concentration, and poor attention to detail (table 1).
The symptoms of inattention typically are not apparent until the child is eight to nine years of age [3,4]. This delay may relate to reduced sensitivity of assessment of attention problems or increased variability in the normal development of the cognitive skills. Similar to the pattern of impulsivity, symptoms of inattention usually are a lifelong problem. (See "Attention deficit hyperactivity disorder in children and adolescents: Overview of treatment and prognosis", section on 'Prognosis'.)
Subtypes of ADHD — Depending upon the predominant symptoms, ADHD can be categorized into one of three subtypes: predominantly inattentive; predominantly hyperactive-impulsive; and combined. The subtype of ADHD in a given patient can change from one to another over time [1,6-8].
The predominantly inattentive subtype of ADHD is characterized by reduced ability to focus attention and reduced speed of cognitive processing and responding [9,10]. Children with the inattentive subtype often are described as having a sluggish cognitive tempo and frequently appear to be daydreaming or "off task" . The typical presenting complaints center on cognitive and/or academic problems. Symptoms may include :
The predominantly hyperactive-impulsive subtype of ADHD is characterized by the inability to sit still or inhibit behavior. Symptoms may include :
Children with the hyperactive-impulsive subtype of ADHD have relatively good attention skills. Cognitive performance may be unaffected . Children with the hyperactive-impulsive subtype of ADHD usually are diagnosed at six to seven years of age, when symptoms of hyperactivity and impulsivity peak.
The combined subtype of ADHD is characterized by symptoms of hyperactivity, impulsivity, and inattention. The combined subtype is the classic subtype of ADHD and the subtype that is most easily identified. Presenting complaints may include disruptive or aggressive behavior, overactivity, disinhibition, and reduced attention span.
Children with the combined subtype of ADHD usually are diagnosed at six to seven years of age, when symptoms of hyperactivity and impulsivity peak.
Impaired functioning — In order to meet criteria for ADHD, core symptoms must impair function in academic, social, or occupational activities . Social skills in children with ADHD often are significantly impaired. Problems with inattention may limit opportunities to acquire social skills or to attend to social cues necessary for effective social interaction, making it difficult to form friendships. Hyperactive and impulsive behaviors may result in peer rejection . The negative consequences of impaired social function (eg, poor self-esteem, increased risk for depression and anxiety) may be long-standing.
DIFFERENTIAL DIAGNOSIS — The symptoms of ADHD overlap with a number of other conditions, including developmental variations, neurologic or developmental conditions, emotional and behavioral disorders, psychosocial or environmental factors, and certain medical problems (table 2) [1,2,14,15]. Some of these conditions can coexist with ADHD and may or may not be responsible for some of the symptoms (eg, children who have learning disabilities may develop inattention as a result of inability to understand new information) . These conditions usually can be differentiated from ADHD with a thorough history and/or the use of a broadband behavior rating scale. If the diagnosis remains uncertain, psychometric testing or a mental health evaluation may be necessary. (See 'Coexisting disorders' below.)
Overview — The evaluation for possible ADHD includes comprehensive medical, developmental, educational, and psychosocial evaluation [2,20-24]. Comprehensive evaluation is necessary to confirm the presence, persistence, pervasiveness, and functional complications of core symptoms (table 1), exclude other explanations for core symptoms (table 2), and identify coexisting emotional, behavioral, and medical disorders. (See 'Diagnostic criteria' below and 'Differential diagnosis' above and 'Coexisting disorders' below.)
The evaluation should include review of the medical, social, and family histories; clinical interviews with the parent and patient; review of information about functioning in school or day care; and evaluation for coexisting emotional or behavioral disorders [20-24]. The necessary information may be obtained in several ways, including in-person discussions, questionnaires, and Web-based tools, as described below.
The complete evaluation may require several office visits . It is important to discuss safety and injury prevention at each visit because children with ADHD or symptoms of ADHD are at increased risk of intentional and unintentional injury compared with children without these symptoms. (See "Attention deficit hyperactivity disorder in children and adolescents: Overview of treatment and prognosis", section on 'Prognosis'.)
Reevaluation of children with ADHD is warranted whenever symptoms worsen or new symptoms emerge because the differential diagnosis of ADHD is extensive and comorbidity is common. (See 'Differential diagnosis' above and 'Coexisting disorders' below.)
Medical evaluation — Important aspects of the medical history include prenatal exposures (eg, tobacco, drugs, alcohol), perinatal complications or infections, central nervous system infection, head trauma, recurrent otitis media, and medications . Family history of similar behaviors is important because ADHD has a strong genetic component. The review of systems should include information about sleep disturbances . It is particularly important to obtain a dietary history (eg, appetite, picking eating) and history of sleep patterns before initiation of pharmacotherapy to avoid attributing preexisting problems to medications . It is also important to obtain a thorough child and family cardiac history and cardiac review of systems before initiating medications. (See "Attention deficit hyperactivity disorder in children and adolescents: Epidemiology and pathogenesis", section on 'Genetic factors' and "Cardiac evaluation of patients receiving pharmacotherapy for attention deficit hyperactivity disorder", section on 'Recommended approach'.)
The pediatric care provider can ask the parents the following questions to elicit concerns regarding school performance and behavior :
The physical examination of most children with ADHD is normal. However, the examination is necessary to evaluate other possibilities in the differential diagnosis. Important aspects of the examination include [21,26]:
Developmental and behavioral evaluation — Important aspects of the developmental and behavioral history include :
The behavioral assessment is focused on determining the age of onset of the core symptoms of ADHD, the duration of symptoms, the settings in which the symptoms occur, and the degree of functional impairment [2,21,22]. This information is necessary to establish the diagnosis of ADHD. (See 'Diagnostic criteria' below.)
Information about the core symptoms can be obtained through the use of open-ended questions or from ADHD-specific rating scales. If open-ended questions are used, the examiner must document the presence of the relevant behaviors from the DSM-IV (table 1).
Behavior rating scales — Various scales have been developed to collect structured observations of behavior (table 4). Completion of these scales by parents and teachers during the diagnostic evaluation helps to establish the presence of core symptoms of ADHD in more than one setting. (See 'Diagnostic criteria' below.)
Educational evaluation — The educational assessment centers on documentation of the core symptoms in the educational setting. Important aspects of the educational evaluation include [2,20]:
The teachers who provide the information should have regular contact with the child for a minimum of four to six months if they are to comment reliably on the persistence of symptoms. In the United States, schools are federally mandated to perform appropriate evaluations (eg, language, cognitive) at no cost to the family if a child is suspected of having a disability that impairs functioning (eg, ADHD or learning disability). (See "Support services for the care of chronically ill children", section on 'Education' and "Definitions of specific learning disability and laws pertaining to learning disabilities", section on 'Laws affecting the education of students with disabilities'.)
Obtaining information about the core symptoms of ADHD from professionals in after-school programs or other structured settings also may be helpful [2,20]. This information may be particularly useful in the evaluation of preschool children and adolescents, or if discrepancies exist between the parents’ and teachers’ reports of core symptoms. When such discrepancies occur, environmental factors (eg, different expectations, levels of structure, or behavior management strategies) may be contributing to the symptoms. (See 'Differential diagnosis' above.)
Coexisting disorders — The evaluation for ADHD should include assessment for coexisting behavior/emotional disorders including oppositional defiant disorder, conduct disorder, depression, anxiety disorder, and learning disabilities (table 5) [21,22,36]. Evaluation for these disorders may include history, broadband behavior scales (oppositional defiant disorder, conduct disorder, depression, anxiety) or psychometric testing (learning disability) (table 2).
Up to one-half of children with ADHD have one or more coexisting behavioral-emotional conditions [37-39]. The coexisting conditions can be primary or secondary (eg, disorders that are exacerbated by the ADHD). In either case, they require treatment in conjunction with treatment for ADHD . (See "Attention deficit hyperactivity disorder in children and adolescents: Overview of treatment and prognosis", section on 'Treatment of coexisting conditions'.)
Anxiety may develop in children with ADHD as a secondary disorder; however, in many cases anxiety appears to be independent of ADHD [37,40].
Children with the combined or hyperactive-impulsive subtype of ADHD are at increased risk for developing coexisting behavior problems, including oppositional defiant disorder [40-42]. Their excessive activity, impulsive response style, and disinhibited emotional expression frequently put them in conflict with parents and other adults. The increased conflict may lead to increased discipline and less positive reinforcement for the child. Under these circumstances, a potentially self-perpetuating pattern of oppositional defiant behavior can emerge (the oppositional acts bring parental attention, which is reinforcing for the child who rarely receives parental praise) [42-44].
Learning disabilities and depression are more common in children with the inattentive and combined subtypes of ADHD [45,46]. Children with ADHD and comorbid mood disorder may have family members with a history of major depressive disorder . During adolescence, they are at increased risk for attempting suicide [48-50]. (See "Specific learning disabilities in children: Clinical features", section on 'Comorbidities' and "Depression in adolescents: Epidemiology, clinical manifestations, and diagnosis", section on 'Epidemiology' and "Suicidal behavior in children and adolescents: Epidemiology and risk factors", section on 'Psychiatric disorder'.)
Adolescents with newly diagnosed ADHD should be assessed for substance abuse . Those with signs and symptoms of substance abuse should undergo evaluation and treatment for addiction before treatment for ADHD with medications (if possible) . (See "Attention deficit hyperactivity disorder in children and adolescents: Treatment with medications", section on 'Prerequisites'.)
Psychometric testing — Psychometric testing is not necessary in the routine evaluation for ADHD and does not distinguish children with ADHD from those without ADHD [22,52]. However, psychometric testing can be valuable in excluding other disorders. The public school system often is the best place to perform psychometric testing (ie, intellectual and academic testing), though more specialized neuropsychological testing requires consultation with a specialist. Testing for learning disabilities can be completed in whole or in part by the school system. (See 'Differential diagnosis' above.)
Children with learning, language, visual-motor, or auditory processing problems can be difficult to distinguish from those with ADHD. These problems tend to be pervasive and persistent and can impair academic function through decreased comprehension or excessive frustration. Children with these problems may attempt to avoid tasks through inattention, getting out of their seats, or impulsively guessing at answers. On the other hand, children with ADHD may perform poorly on language and visual-spatial tasks [53-55], particularly those that require sustained mental effort or are sensitive to impulsive responding (eg, multiple-choice formats).
Comprehensive neuropsychologic testing may help to clarify the diagnosis. Children with learning, language, visual-motor, or auditory processing problems usually perform poorly only in their particular problem area, whereas children with ADHD may perform poorly in several areas of evaluation. Assessment of verbal and nonverbal/performance skills with an intelligence measure such as the Wechsler Intelligence Scale for Children – Fourth Edition  or the Differential Abilities Scale  will help to identify language and/or visual-spatial processing deficits. Assessment of academic skills/achievement testing with a tool such as the Wechsler Individual Achievement Test – Second Edition , or the Wide Range Achievement Test – Fourth Edition  will help to identify potential learning disabilities. (See "Specific learning disabilities in children: Clinical features" and "Specific learning disabilities in children: Evaluation".)
Psychometric testing also can help to identify specific problem areas for children with ADHD, including abstract reasoning, mental flexibility, planning, and working memory, a collection of skills broadly categorized as “executive functions” [9,10,53,60]. Neuropsychological assessment of these skills, as well as direct assessment of attention and behavioral disinhibition, often is desirable to facilitate diagnosis, plan environmental and behavioral interventions, and track progress of treatment [61-64].
Ancillary evaluation — Other evaluations are not routinely indicated to establish the diagnosis of ADHD, but may be warranted to evaluate conditions remaining in the differential diagnosis after the initial assessment. (See 'Differential diagnosis' above.) These evaluations may include [20-22,65]:
Quantitative EEG (qEEG) is a method of analyzing the electrical activity of the brain to derive quantitative patterns that may correspond to diagnostic information and/or cognitive deficits . We do not suggest qEEG for the evaluation of children with ADHD. Although several studies have demonstrated differences in qEEG between children with ADHD and normal children [73-78], the studies were limited by non-random assignment, lack of blinding, failure to consider comorbidities, and/or failure to control for pharmacologic therapy [72,76,79]. Furthermore, the studies did not demonstrate the specificity of the findings for ADHD . Thus, current evidence is insufficient to support the use of qEEG in clinical populations [76,79].
ADHD — The American Psychiatric Association has defined consensus criteria for the diagnosis of ADHD, which are published in the Diagnostic and Statistical Manual of Mental Disorders Fourth Edition Text Revision (DSM-IV-TR) (table 1) . Several features of the DSM-IV-TR criteria deserve emphasis; the symptoms must:
In addition, other physical, situational, or mental health conditions that could account for the symptoms must be excluded. (See 'Differential diagnosis' above.)
Adherence to the DSM-IV-TR criteria can help to minimize over- and underdiagnosis of ADHD. The diagnostic criteria have high interrater reliability for individual items and for overall diagnosis even though the behavioral characteristics specified in the definition are subject to different interpretation by different observers [20,80,81].
Limitations of the DSM-IV-TR criteria include their derivation from studies of children who were evaluated in psychiatric rather than primary care settings and lack of data supporting the number of items required for diagnosis.
The response to stimulant medication cannot be used to confirm or refute the diagnosis of ADHD . Stimulant medications improve behavior in children with ADHD, children with conditions other than ADHD (eg, learning disabilities, depression), and normal control children [82,83].
ADHD subtype — Depending upon the predominant symptoms, ADHD can be categorized into one of three subtypes :
Hyperkinetic disorder — In Europe, the diagnosis of hyperkinetic disorder (HKD) is defined by the International Classification of Diseases (10th edition, ICD-10) criteria (table 6) [21,24]. The ICD-10 criteria for HKD are more restrictive than the DSM-IV criteria for ADHD, requiring that at least six symptoms of inattention, at least three symptoms of hyperactivity, and at least one symptom of impulsivity are present in more than one setting . HKD is subdivided into HKD with and without conduct disorder.
Diagnosis in preschool children — The diagnostic criteria for ADHD (without subtyping) can be applied to children as young as four years of age [2,84]. Longitudinal studies suggest that severe hyperactivity, which is present in only a small subset of preschool children, persists into the school years [85-87].
The criterion that impairment is present in at least two settings may be difficult to meet if the child does not attend preschool or a child care program . In such circumstances, clinicians who suspect ADHD can recommend that the parents attend a parent-training program or that the child be enrolled in a qualified preschool program (eg, Head Start, public prekindergarten programs, Early Childhood Special Education services) . The clinician can then obtain information about core symptoms of ADHD and functional impairment from the instructors of the preschool program or the parenting program (if the child is directly observed).
Diagnosis in adolescents — Establishing a new diagnosis of ADHD in adolescents can be challenging. Adolescents may underreport core symptoms or functional impairment and may spend too little time at home for parents to be accurate informants [2,88]. In such cases, it is important for clinicians to obtain information from at least two teachers and/or other adults with whom the adolescent interacts (eg, guidance counselor, coaches, etc) .
INDICATIONS FOR REFERRAL — Evaluation by a pediatric specialist (eg, a psychologist, psychiatrist, neurologist, educational specialist, or developmental-behavioral pediatrician) is indicated for children in whom the following diagnoses are of concern :
RESOURCES — The National Initiative for Children's Healthcare Quality (NICHQ), in conjunction with North Carolina’s Center for Child Health Improvement, and the American Academy of Pediatrics (AAP), has developed a toolkit to assist primary care practitioners in the evaluation and management of children with ADHD. The toolkit includes information for parents, copies of ADHD-specific questionnaires for parents and teachers, and an initial primary care evaluation form. It can be downloaded without charge through the NICHQ but requires registration. A revised edition of the toolkit, which also includes tools and resources for preschool children and adolescents, is available for purchase through the American Academy of Pediatrics.
Resources for families of children with ADHD are provided in the table (table 7).
Information for teachers of children with ADHD is available through the National Resource Center on ADHD.
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