How is attention-deficit/hyperactivity disorder diagnosed?

Diagnosis of ADHD

To diagnose ADHD, verify that DSM-5 criteria are met by documenting at least 6 symptoms (5 for individuals ≥17 years) of inattention and/or hyperactivity-impulsivity present for ≥6 months, with onset before age 12, functional impairment in at least two settings confirmed by multiple informants (parents/guardians plus at least two teachers or equivalent), and systematic exclusion of alternative causes including trauma, substance use, mood disorders, anxiety, sleep disorders, and learning disabilities. 1, 2

Initial Screening

• Begin with the Adult ADHD Self-Report Scale (ASRS-V1.1) Part A for adults; a positive screen requires endorsing "often" or "very often" on ≥4 of 6 items, which then triggers comprehensive diagnostic evaluation. 1, 3
• For children and adolescents, use DSM-based ADHD rating scales completed by both parents and teachers as screening tools, but never diagnose based on rating scales alone. 1, 4

Mandatory DSM-5 Diagnostic Criteria

Symptom Threshold

• Children and adolescents <17 years: At least 6 symptoms of inattention and/or 6 symptoms of hyperactivity-impulsivity. 1, 4
• Adolescents ≥17 years and adults: At least 5 symptoms of inattention and/or 5 symptoms of hyperactivity-impulsivity. 1, 3, 4

Inattentive Symptoms to Document

• Poor attention to detail, difficulty sustaining attention on tasks, appearing preoccupied even when spoken to directly, difficulty completing tasks due to distraction, organizational challenges resulting in chronic lateness or messiness, reluctance to engage in sustained mental effort, difficulty tracking personal belongings, and easy distractibility. 1

Hyperactive-Impulsive Symptoms to Document

• Frequent fidgeting or tapping, difficulty sitting still for prolonged periods, inner restlessness or agitation, being loud and disruptive, always "on the go," excessive talking, frequently interrupting others, and high impatience. 1

Duration and Onset Requirements

• Symptoms must persist for at least 6 months at a level inconsistent with developmental stage. 1, 4
• Onset before age 12 is mandatory and non-negotiable—obtain reliable historical evidence from childhood through patient recall, collateral informants (family members, partners, close friends), old report cards, school records, or prior evaluations. 1, 2, 3

Cross-Setting Impairment

• Obtain information from at least two teachers (or coaches, school counselors, community activity leaders) plus parents/guardians to demonstrate functional impairment in multiple settings (home, school, work, social relationships). 1, 2, 3
• Document specific examples of how symptoms interfere with or reduce quality of functioning in interpersonal, academic, or occupational domains. 1

Systematic Exclusion of Alternative Diagnoses

Trauma and PTSD

• Screen for post-traumatic stress disorder and complex PTSD, which manifest with impulsivity, hyperarousal, attention difficulties, trauma-specific reexperiencing, avoidance, and emotion dysregulation that closely mimic ADHD but lack pervasive pattern present since before age 12. 2, 3
• Reactive attachment disorder presents with inappropriate social responsivity and behavioral dysregulation that can appear impulsive. 2

Mood and Anxiety Disorders

• Depression and anxiety disorders share hyperarousal features with ADHD but typically lack the pervasive pattern present since childhood; optimize treatment of these conditions before confirming ADHD diagnosis. 1, 2, 3
• Approximately 10% of adults with recurrent depression or anxiety also meet criteria for ADHD, and treating only the mood disorder without addressing co-occurring ADHD is unlikely to restore optimal functioning. 1, 3
• Screen for bipolar disorder because mood instability is common and requires distinct treatment strategies. 3

Substance Use

• Substance use—particularly marijuana, alcohol, and stimulants in adolescents and adults—produces impulsivity, inattention, and hyperactivity identical to ADHD symptoms. 2, 3
• Some adolescents intentionally feign ADHD symptoms to obtain stimulant medications for academic or athletic performance enhancement. 2
• Reassess after sustained abstinence from substance use before confirming ADHD diagnosis. 3

Developmental and Learning Conditions

• Learning disabilities and language disorders commonly present with inattention and behavioral dysregulation that appears impulsive; screen for previously undiagnosed learning disabilities as these persist into adulthood. 2, 3
• Autism spectrum disorder may exhibit impulsive behaviors, poor behavioral regulation, and atypical social responsiveness that mimic ADHD. 2

Physical and Medical Conditions

• Sleep disorders, including obstructive sleep apnea, produce daytime hyperactivity, inattention, and impulsivity that typically improve after treating the underlying sleep problem; obtain detailed sleep history. 2, 3
• Tic disorders can present with motor restlessness and impulsive movements that mimic hyperactivity. 2, 3
• Seizure disorders, particularly absence seizures, can mimic inattention; order appropriate diagnostic tests to exclude medical conditions such as thyroid dysfunction or seizures. 2

Other Psychiatric Conditions

• Oppositional defiant disorder and conduct disorder co-occur with ADHD in approximately 14% of cases; verify that symptoms are not better explained by oppositional behavior, defiance, hostility, or failure to understand tasks. 1, 2
• Psychotic disorders, dissociative disorders, and personality disorders (particularly borderline and antisocial) may present with overlapping symptoms and must be ruled out. 1, 3

Comprehensive Clinical Interview

• Conduct a detailed developmental history focusing on elementary and middle school years to establish childhood onset, asking specific questions about academic performance, peer relationships, and behavioral concerns during those years. 3, 5
• Obtain collateral information from multiple informants—family members, partners, close friends, teachers, or employers—because adults often minimize symptoms and self-report alone is insufficient. 3, 5, 6
• Assess chronicity and pervasiveness of symptoms throughout the lifespan, noting that hyperactive symptoms typically decline while inattentive symptoms persist into adulthood. 3, 7

Validated Assessment Tools

• Use the Conners Adult ADHD Rating Scales (CAARS) for comprehensive symptom assessment with validated normative data in adults, but rating scales do not diagnose ADHD by themselves—clinical interview is mandatory. 3, 6
• For children, conduct clinical interview with parents, examine and observe the child, and obtain information from parents and teachers through DSM-based ADHD rating scales. 1

Age-Specific Considerations

Preschool-Aged Children (4 Years to Sixth Birthday)

• DSM-5 criteria can be applied to preschool-aged children through clinical interview with parents, examination and observation of the child, and information from parents and teachers. 1

Children Younger Than 4 Years

• There is insufficient evidence to support diagnosing or treating ADHD in children younger than 4 years; routine ADHD assessment is not recommended for this age group. 1, 2, 4
• For children <4 years with substantial functional impairment from ADHD-like symptoms, refer families for parent-training programs in behavior management rather than pursuing formal ADHD diagnosis. 2, 4

Common Diagnostic Pitfalls to Avoid

• Failing to obtain information from multiple settings before concluding ADHD criteria are met leads to misdiagnosis; relying solely on parent or teacher reports without corroborating information from multiple sources produces diagnostic errors. 2
• Not establishing that symptoms were present before age 12 in adolescents and adults leads to misdiagnosis of conditions that emerged later, such as depression or substance-induced attentional problems. 2, 3
• Assigning an ADHD diagnosis when symptoms are better explained by trauma, substance use, mood disorders, anxiety, or other psychiatric conditions results in inappropriate treatment and missed opportunities to address the true underlying cause. 2, 3
• Using rating scale scores alone without comprehensive clinical interview and collateral information. 3, 4

Referral Indications

• Refer to child psychiatrist, developmental-behavioral pediatrician, or child psychologist when diagnostic uncertainty exists due to complex comorbidities, atypical presentations, active substance-use disorder, severe mood disorder, treatment-resistant ADHD, or suspected personality disorder. 2, 3, 4
• Referral is indicated when severe mood or anxiety disorders are present that require specialized management before or alongside ADHD treatment. 2, 3

Screening for Comorbidities After ADHD Diagnosis

• Even after meeting ADHD diagnostic thresholds, systematically assess for anxiety (present in approximately 14% of children with ADHD), depression (present in approximately 9% of adults with ADHD), learning disabilities, language disorders, and tic disorders given their high comorbidity rates. 2, 3
• Continuously monitor for new comorbidities—particularly emerging depression and substance-use disorders—throughout ADHD treatment. 3