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 . (See 'Diagnostic criteria' below.)
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 two categories of core symptoms: hyperactivity/impulsivity and inattention. 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 and impulsivity — Hyperactive and impulsive behaviors almost always occur together in young children. The predominantly hyperactive-impulsive subtype of ADHD is characterized by the inability to sit still or inhibit behavior.
Symptoms of hyperactivity and impulsivity may include :
●Excessive fidgetiness (eg, tapping the hands or feet, squirming in seat)
●Difficulty remaining seated when sitting is required (eg, at school, work, etc)
●Feelings of restlessness (in adolescents) or inappropriate running around or climbing in younger children
●Difficulty playing quietly
●Difficult to keep up with, seeming to always be "on the go"
●Difficulty waiting turns
●Blurting out answers too quickly
●Interruption or intrusion of others
Hyperactive and impulsive symptoms typically are observed by the time the child reaches four years of age and increase during the next three to four years, peaking in severity when the child is seven to eight years of age [3,4]. After seven to eight years of age, hyperactive symptoms begin to decline; by the adolescent years, they may be barely discernible to observers, although the adolescent may continue to feel restless or unable to settle down . In contrast, impulsive symptoms usually persist throughout life. Symptoms of impulsivity in adolescents include substance use, risky sexual behavior, and impaired driving . (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 — The predominantly inattentive presentation of ADHD is characterized by reduced ability to focus attention and reduced speed of cognitive processing and responding [8,9]. 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. Among children born at <32 weeks gestational age, symptoms of inattention appear to be more prominent than hyperactivity and impulsivity . (See "Long-term neurodevelopmental impairment in infants born preterm: Epidemiology and risk factors", section on 'Risk of NDI by gestational age'.)
Symptoms of inattention may include :
●Failure to provide close attention to detail, careless mistakes
●Difficulty maintaining attention in play, school, or home activities
●Seems not to listen, even when directly addressed
●Fails to follow through (eg, homework, chores, etc)
●Difficulty organizing tasks, activities, and belongings
●Avoids tasks that require consistent mental effort
●Loses objects required for tasks or activities (eg, school books, sports equipment, etc)
●Easily distracted by irrelevant stimuli
●Forgetfulness in routine activities (eg, homework, chores, morning routines, etc)
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 . In adolescents, symptoms of inattention may result in academic difficulty . (See "Attention deficit hyperactivity disorder in children and adolescents: Overview of treatment and prognosis", section on 'Prognosis'.)
Impaired functioning — 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.
Indications and process — Evaluation for ADHD should be initiated in children ≥4 years of age who have symptoms of inattention, hyperactivity, or impulsivity or who have complaints frequently associated with ADHD (eg, poor school performance, difficulty making and keeping friends, difficulty with team sports) .
The evaluation for possible ADHD includes comprehensive medical, developmental, educational, and psychosocial evaluation [2,6,14-19].
Comprehensive evaluation is necessary to confirm the presence, persistence, pervasiveness, and functional complications of core symptoms, exclude other explanations for core symptoms (table 1), and identify coexisting emotional, neurodevelopmental, behavioral, and medical disorders. (See 'Diagnostic criteria' below and 'Differential diagnosis' below and 'Evaluation for coexisting disorders' below.)
The evaluation should include review of the medical, social, and family histories; clinical interviews with the caregiver and patient; review of information about functioning in school or day care; and evaluation for coexisting emotional, neurodevelopmental, or behavioral disorders [6,14-17,19]. The necessary information may be obtained in several ways, including in-person discussions, questionnaires, and web-based tools, as described in the sections 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' below and 'Evaluation for coexisting disorders' below.)
●History – 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. (See "Attention deficit hyperactivity disorder in children and adolescents: Epidemiology and pathogenesis", section on 'Genetic factors'.)
The review of systems should include information about sleep disturbances [6,20]. It is particularly important to obtain a dietary history (eg, appetite, picky 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 "Sleep in children and adolescents with attention deficit hyperactivity disorder" and "Cardiac evaluation of patients receiving pharmacotherapy for attention deficit hyperactivity disorder", section on 'Pretreatment clinical evaluation'.)
The psychosocial history should include questions about environmental exposures (eg, lead, tobacco smoke), family stress, problematic relationships, and adverse childhood experiences (ACEs), which can affect the child's general functioning .
To elicit concerns regarding school performance and behavior, the pediatric care provider can ask :
•How the child is doing at school
•Whether the caregiver or the teacher has noticed any problems with learning
•Whether the child is happy in school
•Whether the child has any behavioral problems at school or home, or when playing with friends
•Whether the child has problems completing school assignments at school or home
●Physical examination – 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 [6,14,21]:
•Measurement of height, weight, head circumference, and vital signs
•A complete neurologic examination, including assessment of vision and hearing, assessment of coordination, observation for verbal or motor tics
•Observation of the child's behavior in the office setting; however, this isolated assessment of behavior should be interpreted cautiously; symptoms of ADHD may not be apparent in the structured setting of the clinic visit, or nervousness/apprehension could be misinterpreted as symptoms of ADHD
•Observation of the child's communication skills, particularly nonverbal and pragmatic communication (ie, ability to successfully use language in context), which are impaired in children with autism spectrum disorder (ASD), an important consideration in the differential diagnosis (see "Autism spectrum disorder in children and adolescents: Clinical features", section on 'Nonverbal and pragmatic communication behaviors')
Developmental and behavioral evaluation
Behavior assessment and history — Important aspects of the developmental and behavioral history include :
●Specific information about the onset, course, and functional impact of ADHD symptoms
●Emotional, medical, and developmental events that may provide an alternative explanation for the symptoms (see 'Differential diagnosis' below)
●Developmental milestones, particularly language milestones (table 2)
●Psychosocial stressors, including any ACEs such as food insecurity, homelessness, neglect, community violence [22,23]
●Observation of caregiver-child interactions
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 [2,14,15]. 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 Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision (DSM-5-TR). (See 'Diagnostic criteria' below.)
Behavior rating scales — Various scales have been developed to collect structured observations of behavior (table 3). Completion of these scales by parents or caregivers and teachers during the diagnostic evaluation helps to establish the presence of core symptoms of ADHD in more than one setting. Although the rating scales may identify symptoms of ADHD, rating scales do not determine whether the symptoms are due to ADHD and are subject to the interpretation of the rater (who may misunderstand the behaviors), and rating scales may not provide information about contextual influences (eg, what happened before the behaviors occurred) . Rating scales derived from ADHD criteria in the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) can be used if rating scales derived from DSM-5 criteria are not available because the core symptoms of ADHD in DSM-IV and DSM-5 are virtually identical . (See 'Diagnostic criteria' below.)
●ADHD-specific scales – ADHD-specific rating scales (also called narrow-band scales) focus directly on the symptoms of ADHD and can be used to establish the presence of the core symptoms of ADHD. The validity of ADHD rating scales in distinguishing children with ADHD from age-matched control children varies depending upon the age of the child, the scale that is used, and the informant (eg, parent or caregiver, teacher, adolescent) .
ADHD-specific rating scales have a sensitivity and specificity of greater than 90 percent when used in an appropriate population [24,25]. However, most of the studies validating the use of rating scales have taken place in referral rather than primary care settings. The first edition of the National Institute for Children's Healthcare Quality (NICHQ) ADHD toolkit includes the Vanderbilt Assessment Scales, which can be downloaded and printed from the website. The Vanderbilt Assessment Scales have been validated in both community and referral settings using longitudinal assessment and follow-up [26-28].
Only the Conners Comprehensive Behavior Rating Scales and the ADHD Rating Scale IV have been validated in preschool-aged children (ie, age four through five years) [2,29]. The ADHD Rating Scale-5 has been validated in children age 5 through 17 years . The Vanderbilt rating scales were not designed for preschool children but can be used in children ≥4 years because the DSM-5/DSM 5-TR behavioral criteria for ADHD are the same for children age 4 through 17 years [1,2,31-33].
●Broadband scales – Broadband scales assess a variety of behavioral symptoms, including, but not limited to, the core symptoms of ADHD; they assess internalizing behaviors (eg, feeling depressed, anxious, withdrawn) and externalizing behaviors other than ADHD (eg, aggression). Broadband scales (with the exception of the Conners' Long form) are not recommended to establish the presence of the core symptoms of ADHD because they are less sensitive and specific (<86 percent) than ADHD-specific scales . However, broadband scales can help to identify coexisting conditions and narrow the differential diagnosis . (See "Developmental-behavioral surveillance and screening in primary care", section on 'Choice of screening test'.)
Educational evaluation — The educational assessment centers on documentation of the core symptoms in the educational setting. Important aspects of the educational evaluation include [2,6]:
●Completion of an ADHD-specific rating scale (see 'Behavior rating scales' above)
●A narrative summary of classroom behavior and interventions, learning patterns, and functional impairment
●Copies of report cards and samples of schoolwork
●Review of school-based multidisciplinary evaluations (if such evaluations have been performed)
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, public 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 disorder). (See "Definitions of specific learning disorder and laws pertaining to learning disorders in the United States", section on 'Laws affecting the education of students with disabilities' and "Children and youth with special health care needs", section on 'School-based services'.)
Obtaining information about the core symptoms of ADHD from professionals in after-school programs or other structured settings also may be helpful [2,6]. This information may be particularly useful in the evaluation of preschool children and adolescents, or if discrepancies exist between the caregivers' 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' below.)
Evaluation for coexisting disorders — The evaluation for ADHD should include assessment for coexisting developmental, cognitive, physical, and behavioral/emotional disorders because coexisting disorders are common among children with ADHD, require treatment in conjunction with ADHD, and may affect the treatment for ADHD [2,35-41]. (See "Attention deficit hyperactivity disorder in children and adolescents: Overview of treatment and prognosis", section on 'Treatment of coexisting conditions'.)
Urgent evaluation is necessary for children with suicidal ideation or the potential to harm themselves or others (eg, children with severe outbursts of anger) .
Common coexisting disorders are listed below. The evaluation for most of these disorders is discussed separately:
●Learning disorders (see "Specific learning disorders in children: Evaluation")
●Language disorder (see "Evaluation and treatment of speech and language disorders in children")
●Developmental coordination disorder (see "Developmental coordination disorder: Clinical features and diagnosis")
●Sleep disorders (see "Assessment of sleep disorders in children")
●Depression and suicidality (see "Pediatric unipolar depression: Epidemiology, clinical features, assessment, and diagnosis", section on 'Epidemiology' and "Suicidal behavior in children and adolescents: Epidemiology and risk factors", section on 'Psychiatric disorder')
●Anxiety (see "Anxiety disorders in children and adolescents: Epidemiology, pathogenesis, clinical manifestations, and course" and "Anxiety disorders in children and adolescents: Assessment and diagnosis")
●Substance use (see "Attention deficit hyperactivity disorder in children and adolescents: Treatment with medications", section on 'Prerequisites' and "Substance use disorder in adolescents: Epidemiology, clinical features, consequences, screening, and diagnosis")
●Oppositional defiant disorder – Oppositional defiant disorder (ODD) is characterized by a persistent pattern of angry or irritable mood, argumentative or defiant behavior, and vindictiveness that is associated with distress in the patient or close contacts or impairs ability to function in social, school, work, or other settings . Broadband behavior scales can be used as a preliminary screen for ODD. (See "Oppositional defiant disorder: Epidemiology, clinical manifestations, course, and diagnosis".)
●Conduct disorder – Conduct disorder is characterized by a persistent pattern of aggression toward people or animals, destruction of property, deceitfulness or theft, and serious violation of rules that affects ability to function in social, school, or work settings . Broadband behavior scales can be used as a preliminary screen for conduct disorder.
Ancillary evaluation for select patients — Other evaluations are not routinely indicated to establish the diagnosis of ADHD but may be warranted to evaluate comorbid conditions or conditions remaining in the differential diagnosis after the initial assessment. (See 'Differential diagnosis' below.) These evaluations may include [6,14,15,44]:
●Speech and language evaluation (language or communication disorder) (see "Evaluation and treatment of speech and language disorders in children", section on 'Speech and language evaluation')
●Occupational therapy evaluation (motor coordination disorder) (see "Developmental coordination disorder: Clinical features and diagnosis", section on 'Clinical features')
●Mental health evaluation (mood disorder, anxiety, oppositional defiant disorder, conduct disorder, obsessive-compulsive disorder, posttraumatic stress disorder, adjustment disorder) (see 'Evaluation for coexisting disorders' above and 'Indications for referral' below)
●Blood lead level (lead poisoning) [45,46] (see "Childhood lead poisoning: Clinical manifestations and diagnosis")
●Thyroid hormone levels (thyroid disorder)  (see "Clinical manifestations and diagnosis of Graves disease in children and adolescents", section on 'Diagnostic evaluation')
●Genetic testing and/or genetics consultation (fragile X syndrome) [48,49] (see "Fragile X syndrome: Clinical features and diagnosis in children and adolescents", section on 'Diagnosis')
●Overnight polysomnography for children with symptoms suggestive of and/or risk factors for obstructive sleep apnea syndrome, restless legs syndrome, or circadian rhythm disorder (see "Evaluation of suspected obstructive sleep apnea in children" and "Restless legs syndrome and periodic limb movement disorder in children")
●Neurology consultation or EEG (electroencephalography; neurologic or seizure disorder) (see "Seizures and epilepsy in children: Clinical and laboratory diagnosis")
●Psychological or neuropsychological testing – Psychological testing (ie, cognitive and academic testing) is not necessary in the routine evaluation for ADHD and does not distinguish children with ADHD from those without ADHD [15,50,51]. It is, however, recommended in the evaluation for complex ADHD . Psychological testing can help to exclude other disorders (eg, learning disorder) or 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" [8,9,52,53]. Neuropsychologic 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 [54-57].
The public school system often is the best place to obtain basic psychometric testing, though more specialized neuropsychologic testing requires consultation with a specialist. Testing for learning disorders can be completed in whole or in part by the school system. (See "Specific learning disorders in children: Role of the primary care provider", section on 'Requesting evaluation in the school district'.)
Tests not routinely recommended
Quantitative EEG — Quantitative electroencephalography (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 the US Food and Drug Administration has licensed the first EEG test for assessment of children (6 to 17 years of age) for ADHD  and several studies have demonstrated differences in qEEG between children with ADHD and normal children [60-65], the studies were limited by nonrandom assignment, lack of blinding, failure to consider comorbidities, and/or failure to control for pharmacologic therapy [58,63,66]. In addition, the EEG patterns differ in males and females . A 2013 meta-analysis of nine studies (including 1253 children with ADHD and 517 without ADHD) found significant heterogeneity and concluded that EEG profiles (specifically an increased theta to beta ratio) cannot be used to reliably diagnose ADHD (although they may be helpful for prognosis) . Evidence is insufficient to support the use of qEEG over clinical evaluation of symptoms and functional impairment for the diagnosis of ADHD [18,69]. (See 'Diagnosis' below.)
●DSM-5-TR – 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, Fifth Edition, Text Revision (DSM-5-TR) . For children <17 years, the DSM-5-TR diagnosis of ADHD requires ≥6 symptoms of hyperactivity and impulsivity or ≥6 symptoms of inattention. For adolescents ≥17 years and adults, ≥5 symptoms of hyperactivity and impulsivity or ≥5 symptoms of inattention are required. (See 'Hyperactivity and impulsivity' above and 'Inattention' above.)
The symptoms of hyperactivity/impulsivity or inattention must :
•Be present in more than one setting (eg, school and home)
•Persist for at least six months
•Be present before the age of 12 years
•Impair function in academic, social, or occupational activities
•Be excessive for the developmental level of the child
In addition, other physical, situational, or mental health conditions that could account for the symptoms must be excluded. (See 'Differential diagnosis' below.)
Adherence to the DSM-5-TR criteria can help to minimize over- and under-diagnosis 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 [70,71].
Limitations of the DSM-5-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. In addition, the criterion that symptoms of hyperactivity/impulsivity or inattention be present before the age of 12 years is controversial. (See "Attention deficit hyperactivity disorder in adults: Epidemiology, clinical features, assessment, and diagnosis", section on 'Course'.)
Positive or negative 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 disorders, depression), and normal control children [72,73].
●ICD-11 – In other countries, the ADHD is defined by the International Classification of Diseases (11th edition, ICD-11) criteria for ADHD (table 4) . In the 10th edition, ADHD was called hyperkinetic disorder.
ADHD presentations — Depending upon the predominant symptoms, ADHD can be categorized into one of the three presentations listed below [1,74]. The presentation of ADHD in a given patient can change from one to another over time [1,75-77].
•DSM-5-TR criteria require ≥6 symptoms of inattention for children <17 years; ≥5 symptoms for adolescents ≥17 years and adults and <6 symptoms of hyperactivity-impulsivity  (see 'Inattention' above)
•ICD-11 specifies that all diagnostic requirements for ADHD are met and inattentive symptoms predominate
•DSM-5-TR criteria require ≥6 symptoms of hyperactivity-impulsivity for children <17 years; ≥5 symptoms for adolescents ≥17 years and adults and <6 symptoms of inattention  (see 'Hyperactivity and impulsivity' above)
•ICD-11 specifies that all diagnostic requirements for ADHD are met and hyperactive/impulsive symptoms predominate
•DSM-5-TR criteria require ≥6 symptoms of inattention and ≥6 symptoms of hyperactivity-impulsivity for children <17 years; ≥5 symptoms in each category for adolescents ≥17 years and adults  (see 'Inattention' above and 'Hyperactivity and impulsivity' above)
•ICD-11 specifies that all diagnostic requirement for ADHD are met and neither inattentive nor hyperactive/impulsive symptoms clearly predominate
Diagnosis in preschool children — The diagnostic criteria for ADHD (without subtyping) can be applied to children as young as four years of age [2,78]. Longitudinal studies suggest that severe hyperactivity, which is present in only a small subset of preschool children, persists into the school years [79-82].
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 caregivers attend a parent/caregiver training program or that the child be enrolled in a qualified preschool program (eg, Head Start, public prekindergarten programs, Early Childhood Special Education services) [2,51]. 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).
If caregiver and teacher ratings are discordant, differing expectations and environmental factors should be considered (eg, structure, rules, adult authority) [6,83]. (See 'Differential diagnosis' below.)
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 caregivers to be accurate informants [2,5,84]. 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, tutor, coach, etc) . Strict adherence to the criterion that symptoms of hyperactivity/impulsivity or inattention be present before the age of 12 years may fail to identify adolescents and adults with more subtle attentional or organizational problems or adolescents who have above average cognitive abilities. (See "Attention deficit hyperactivity disorder in adults: Epidemiology, clinical features, assessment, and diagnosis", section on 'Diagnosis'.)
Adolescents being evaluated for ADHD should be interviewed privately . Although adolescent patients may not accurately report their symptoms or strengths and weaknesses , they may provide other important information unknown to or undisclosed by caregivers or teachers (eg, symptoms of depression or anxiety, risky behaviors, substance use or misuse of prescription drugs, bullying, information about the home environment) .
When considering a diagnosis of "late onset" ADHD in adolescents and young adults, it is particularly important to obtain a psychiatric history and assessment of current functioning, ideally from multiple sources. In long-term follow-up of a randomized trial, 239 individuals without childhood ADHD underwent at least two comprehensive assessments for ADHD between baseline (mean age 10 years) and young adulthood (mean age 24 years) . Although 143 screened positive on symptom checklists in adolescence or young adulthood, late-onset ADHD was excluded in approximately 95 percent by lack of clinical impairment, lack of cross-situational confirmation (eg, parents/caregivers, teachers, other informants), or an alternative explanation for symptoms (eg, substance use, another mental illness).
Another possible explanation for new onset of ADHD symptoms in adolescents is frequent digital media use (eg, checking social media, playing games alone, video chatting). In a longitudinal cohort of 2587 15- and 16-year-olds who did not have self-reported symptoms of ADHD at baseline, self-reported higher-frequency digital media use was associated with self-reported ADHD symptoms over two years of follow-up . The frequent distraction and rapid feedback of digital media may disrupt normal development of sustained attention, impulse control, and ability to delay gratification. In addition, digital media may displace other activities that build attention span and executive function [87,88]. It remains to be determined whether symptoms that develop in response to media use require or respond to typical ADHD treatments.
Finally, it is important to consider the possibility that adolescent patients may intentionally misreport or misrepresent their symptoms for various reasons (eg, to obtain medications, school accommodations, or accommodations for standardized testing) [6,89].
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 1) [1,2,90-92]. Some of these conditions coexist with ADHD and may or may not be responsible for some of the symptoms (eg, children who have learning disorders may exhibit inattention as a result of difficulties learning 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, psychological testing or a mental health evaluation may be necessary. (See 'Evaluation for coexisting disorders' above.)
●Developmental variations – Developmental variations include intellectual disability, giftedness, and behaviors that are within the normal range for the child's level of development and do not impair function (eg, a short attention span or increased motor activity in a preschool child; occasional impulsivity in a school-age child) [90,91]. (See "Intellectual disability (ID) in children: Clinical features, evaluation, and diagnosis" and "Intellectual disability in children: Evaluation for a cause".)
When considering behaviors that are within the normal range for the child's level of development, relative age and maturity within a specific grade are more important than the grade level itself [94,95]. In observational studies, younger age for a particular grade level has been associated with increased diagnosis of and treatment for ADHD in children [96-99], suggesting that developmental immaturity may account for some behaviors that are attributed to ADHD and highlighting the importance of adhering to ADHD diagnostic criteria for diagnosis.
Children with developmental variations do not meet the full criteria for ADHD. (See 'Diagnostic criteria' above.)
●Neurologic or developmental conditions – Neurodevelopmental conditions that can mimic or co-occur with ADHD are listed below [90,100,101]. These disorders usually can be distinguished from ADHD through history and examination. Specialized testing may be necessary in some circumstances.
•Learning disorders or language/communication disorders (see "Specific learning disorders in children: Clinical features" and "Etiology of speech and language disorders in children")
Children with learning, language, visual-motor, or auditory processing problems can be difficult to distinguish from those with ADHD. Similar to ADHD, these problems tend to be pervasive and persistent and can impair academic function. Children with these problems may attempt to avoid tasks through inattention, getting out of their seats, or impulsively guessing at answers. Similar to children with these problems, children with ADHD may perform poorly on language and visual-spatial tasks [52,102,103], particularly those that require sustained mental effort or are sensitive to impulsive responding (eg, multiple-choice formats).
Comprehensive neuropsychological 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. (See "Specific learning disorders in children: Evaluation", section on 'Comprehensive evaluation'.)
-Assessment of verbal and nonverbal/performance skills with an intelligence measure such as the Wechsler Intelligence Scale for Children – Fifth Edition  or the Differential Abilities Scale-II  will help to identify language and/or visual-spatial processing deficits, as well as learning disorders.
-Assessment of academic skills/achievement testing with a tool such as the Wechsler Individual Achievement Test – Fourth Edition  or the Wide Range Achievement Test – Fifth Edition  will help to identify potential learning disorders.
•Autism spectrum disorders (ASD); it is particularly important to consider ASD in preschool children with symptoms of ADHD  (see "Autism spectrum disorder in children and adolescents: Clinical features")
•Neurodevelopmental syndromes, for example:
-Fragile X syndrome (see "Fragile X syndrome: Clinical features and diagnosis in children and adolescents")
-Fetal alcohol syndrome (see "Fetal alcohol spectrum disorder: Clinical features and diagnosis")
-Klinefelter syndrome (see "Clinical features, diagnosis, and management of Klinefelter syndrome")
-Childhood cerebral adrenoleukodystrophy (ALD) (see "Clinical features, evaluation, and diagnosis of X-linked adrenoleukodystrophy", section on 'Leukodystrophy')
Genetic testing may be necessary to distinguish fragile X syndrome, Klinefelter syndrome, or childhood cerebral ALD from ADHD.
•Seizure disorder; electroencephalography may be necessary to distinguish a seizure disorder from ADHD (see "Seizures and epilepsy in children: Classification, etiology, and clinical features")
•Sequelae of central nervous system infection or trauma (see "Bacterial meningitis in children: Neurologic complications", section on 'Intellectual and behavioral disabilities')
•Metabolic disorders (eg, adrenoleukodystrophy, mucopolysaccharidosis type III) (see "Clinical features, evaluation, and diagnosis of X-linked adrenoleukodystrophy" and "Mucopolysaccharidoses: Clinical features and diagnosis", section on 'MPS type III (Sanfilippo syndrome)')
•Motor coordination disorders (eg, developmental coordination disorder); occupational therapy evaluation may be necessary to distinguish motor coordination disorders from ADHD (see "Developmental coordination disorder: Clinical features and diagnosis")
●Emotional and behavioral disorders – Emotional and behavioral disorders that can mimic or co-occur with ADHD include anxiety disorder, mood disorders, oppositional defiant disorder, conduct disorder, obsessive-compulsive disorder, substance use disorder, posttraumatic stress disorder, and adjustment disorder. The use of a broadband behavior scale may be helpful in the assessment of these disorders. However, evaluation by a mental health professional generally is necessary for diagnosis. (See 'Evaluation for coexisting disorders' above and 'Behavior rating scales' above and 'Indications for referral' below.)
●Psychosocial and environmental factors – Environmental factors that can contribute to inattention, impulsivity, or hyperactivity include a stressful home environment, an inappropriate educational setting, less structure and fewer rules at home than at school, and high-frequency digital media use. Psychosocial factors that may contribute to caregiver-reports of inattention, impulsivity, or hyperactivity include increased caregiver stress or mental health problems (eg, depression) . (See 'Diagnosis in adolescents' above.)
In contrast to ADHD, psychosocial and environmental factors generally affect behavior only in one setting (eg, at home but not at school, or at school but not at home). Caregiver-child temperament or "personality" mismatch and caregiver mental health conditions (particularly maternal depression) can contribute to caregiver report of ADHD-type symptoms in the home setting. However, caregivers of ADHD children with limited resources or support may also develop stress-related mental health conditions; in such circumstances, multiple respondent (eg, teacher, coach) reports help to confirm the diagnosis of ADHD.
●Adverse childhood experiences – Exposure to adverse childhood experiences (ACEs) such as physical or emotional abuse, chronic neglect, chronic family hardship or mental illness, or community violence can lead to a prolonged stress response ("toxic stress") that has been shown to disrupt early brain development and cause permanent changes in brain architecture and subsequent neurodevelopment . Children exposed to ACEs are at higher risk for developing ADHD as well as other psychopathology [22,23]. A comprehensive psychosocial history including screening for ACEs can identify these risks and help tailor treatment.
●Medical conditions – Medical conditions that may have clinical features that mimic ADHD include hearing or visual impairment, lead poisoning, thyroid abnormalities, sleep disorders (eg, obstructive sleep apnea, restless leg/periodic limb movement disorder), tics, and medication effects (eg, albuterol) [6,20,109]. Symptoms of these conditions fluctuate with the disease course or exposure to medication. In contrast, the symptoms in ADHD are persistent and pervasive.
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 or complicate the diagnosis of ADHD [2,41]:
●Developmental disorder (eg, speech or motor delay)
●Visual or hearing impairment
●History of abuse or exposure to one or more adverse childhood experiences
●Coexisting learning and/or emotional problems
●Chronic illness that requires treatment with a medication that interferes with learning
●Children who continue to have problems in functioning despite treatment (see "Attention deficit hyperactivity disorder in children and adolescents: Overview of treatment and prognosis", section on 'Response to treatment')
RESOURCES — The National Institute for Children's Healthcare Quality (NICHQ), in conjunction with North Carolina's Center for Child Health Improvement, and the American Academy of Pediatrics (AAP), developed a toolkit to assist primary care practitioners in the evaluation and management of children with ADHD. The first edition of the toolkit includes information for caregivers, copies of ADHD-specific questionnaires for parents/caregivers and teachers, and an initial primary care evaluation form. It can be downloaded without charge through the NICHQ. The third edition of the toolkit, which also includes tools and resources for preschool children and adolescents, is available for purchase through the AAP.
Resources for caregivers of children with ADHD are provided in the table (table 5).
Information for teachers of children with ADHD is available through Children and Adults with Attention-Deficit/Hyperactivity Disorder.
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Attention deficit hyperactivity disorder".)
INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or email these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient education" and the keyword[s] of interest.)
●Beyond the Basics topics (see "Patient education: Symptoms and diagnosis of attention deficit hyperactivity disorder in children (Beyond the Basics)" and "Patient education: Treatment of attention deficit hyperactivity disorder in children (Beyond the Basics)")
SUMMARY AND RECOMMENDATIONS
●Clinical features – Attention deficit hyperactivity disorder (ADHD) is a behavioral condition with persistent and pervasive core symptoms of inattention, hyperactivity, and impulsivity. The symptoms affect cognitive, academic, behavioral, emotional, and social functioning. (See 'Clinical features' above.)
●Evaluation – Evaluation for ADHD should be initiated in children ≥4 years of age who have symptoms of inattention, hyperactivity, or impulsivity or who have complaints frequently associated with ADHD (eg, poor school performance, difficulty making and keeping friends, difficulty with team sports). (See 'Indications and process' above.)
Evaluation for ADHD requires comprehensive medical, developmental, educational, and psychosocial evaluation to confirm the presence, persistence, pervasiveness, and functional complications of core symptoms, exclude other causes of core symptoms (table 1), and identify coexisting emotional, behavioral, and medical disorders (eg, anxiety, mood disorders, learning disorder, sleep disorders). (See 'Medical evaluation' above and 'Evaluation for coexisting disorders' above.)
The evaluation for ADHD requires information about the child's behavior in more than one setting (eg, home and school or after-school program). ADHD-specific behavior scales (table 3) can be used to gather this information from the parents/caregivers and teacher(s). (See 'Educational evaluation' above and 'Behavior rating scales' above.)
●Ancillary evaluation – The evaluation for ADHD does not require blood lead levels, thyroid hormone levels, neuroimaging, electroencephalography, or psychological testing unless these tests are indicated by findings in the clinical evaluation or to narrow the differential diagnosis and plan the approach to management. (See 'Ancillary evaluation for select patients' above.)
●Diagnostic criteria – The diagnosis of ADHD requires that the child meet the criteria defined by the Diagnostic and Statistical Manual of Mental Disorders Fifth Edition, Text Revision or the International Classification of Diseases (table 4). The response to stimulant medication cannot be used to confirm or refute the diagnosis. (See 'Diagnostic criteria' above.)
●Differential diagnosis – The differential diagnosis for ADHD includes developmental variations, neurologic or developmental conditions, emotional and behavioral disorders, psychosocial or environmental factors, and certain medical problems (table 1). Most of these conditions may coexist with ADHD and require simultaneous treatment. Given the broad differential diagnosis of ADHD and frequency of coexisting conditions, reevaluation of children with ADHD is warranted whenever symptoms worsen or new symptoms emerge. (See 'Differential diagnosis' above and 'Evaluation for coexisting disorders' above.)
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