What are the diagnostic criteria for Attention Deficit Hyperactivity Disorder (ADHD)?

ADHD Diagnostic Criteria

To diagnose ADHD, you must verify that DSM-5 criteria are met: at least 5 symptoms (6 for children under 17) from either inattention or hyperactivity-impulsivity domains, persisting for at least 6 months, with onset before age 12, present in two or more settings, causing functional impairment, and not better explained by another mental disorder. 1, 2

Core Symptom Requirements

The diagnosis hinges on two distinct symptom domains, and patients must meet threshold criteria in at least one 1:

Inattention Symptoms (need ≥5 for adults ≥17 years; ≥6 for younger patients):

• Poor attention to detail or careless mistakes 1
• Difficulty sustaining attention on tasks 1
• Appears preoccupied, difficulty shifting focus even when directly addressed 1
• Fails to complete tasks due to distraction 1
• Organizational challenges causing chronic lateness, messiness, or disorganized work 1
• Avoids tasks requiring sustained mental effort 1
• Loses personal belongings or items needed for tasks 1
• Easily distracted by external stimuli 1
• Forgetful in daily activities 1

Hyperactivity-Impulsivity Symptoms (need ≥5 for adults ≥17 years; ≥6 for younger patients):

• Frequent fidgeting such as tapping 1
• Difficulty remaining seated for prolonged periods 1
• Inner restlessness or agitation 1
• Often loud and disruptive 1
• Always "on the go," difficult for others to keep pace 1
• Talks excessively 1
• Blurts out answers or interrupts others in conversation 1
• Highly impatient, struggles waiting in line 1
• Intrudes into others' activities 1

Three Clinical Presentations

Based on which symptom domain predominates, classify as 1:

• Predominantly Inattentive: ≥5 inattention symptoms but <5 hyperactivity-impulsivity symptoms for ≥6 months 1
• Predominantly Hyperactive-Impulsive: ≥5 hyperactivity-impulsivity symptoms but <5 inattention symptoms for ≥6 months 1
• Combined Presentation: ≥5 symptoms from both domains for ≥6 months 1

Mandatory Temporal and Developmental Criteria

Symptoms must have been present before age 12 years—this is non-negotiable. 1, 2 For adults presenting for evaluation, you must establish retrospective evidence of childhood onset through detailed history, even when formal documentation is absent 2. The DSM-5 increased this age threshold from 7 years (DSM-IV) to 12 years, recognizing that some patients don't come to clinical attention until later childhood 1.

Symptoms must persist for at least 6 months to distinguish ADHD from transient behavioral problems 1, 2.

Cross-Situational Impairment Requirement

You must document functional impairment in more than one major setting—home, school, work, or social contexts. 1, 2, 3 This is critical: symptoms confined to a single environment suggest situational factors rather than ADHD 1.

Gather information systematically from multiple informants 1, 2:

• Parents or guardians 1
• Teachers or school personnel 1
• Workplace supervisors (for adults) 1
• Mental health clinicians already involved 1
• Spouse or close family members who know the patient well 1

Systematic Assessment Approach

Initial Screening

For adults, begin with the Adult ADHD Self-Report Scale (ASRS-V1.1) Part A 1, 2. A positive screen requires the patient to endorse "often" or "very often" for 4 or more of the 6 questions 1.

For children ages 4-18 presenting with academic or behavioral problems plus symptoms of inattention, hyperactivity, or impulsivity, initiate a formal ADHD evaluation 1, 3.

Comprehensive Evaluation

If screening is positive, proceed with 1:

• Part B of the ASRS to fully characterize symptoms 1
• DSM-based ADHD rating scales completed by parents and teachers (for children) 1, 2
• Clinical interview with the patient 1
• Direct observation of the child (for pediatric cases) 1
• Collateral information from someone who knows the patient well 1

The Vanderbilt ADHD Rating Scales are specifically recommended by the American Academy of Pediatrics for children ages 6-12 years, with both parent and teacher versions required. 3

Ruling Out Alternative Explanations

Before finalizing the diagnosis, systematically exclude 1:

• Oppositional behavior, defiance, or hostility 1
• Failure to understand tasks or instructions 1
• Other mental disorders: psychotic disorders, mood disorders, anxiety disorders, dissociative disorders, personality disorders 1
• Substance intoxication or withdrawal 1

Mandatory Comorbidity Screening

You must screen for comorbid conditions because they occur frequently and alter treatment approach. 1, 3 Systematically assess for 3:

• Emotional/behavioral conditions: anxiety, depression, oppositional defiant disorder, conduct disorders, substance use 3
• Developmental conditions: learning disabilities, language disorders, autism spectrum disorders 3
• Physical conditions: tics, sleep apnea, sleep disorders 3

Around 10% of adults with recurrent depression or anxiety have ADHD, and treating depression/anxiety alone will likely fail to restore optimal functioning if ADHD remains unaddressed 1.

Special Considerations for Preschool-Aged Children (Ages 4-5)

DSM-5 criteria can be applied to preschool-aged children, but determining symptom presence is more challenging in this age group 1. Conduct a clinical interview with parents, examine and observe the child directly, and obtain DSM-based rating scales from parents and teachers 1. The Conners Rating Scale has preschool-age normative data that can be used 3.

For children under age 4 with ADHD-like symptoms causing substantial impairment, consider referral for parent training in behavior management rather than pursuing formal diagnosis 1.

Critical Pitfalls to Avoid

• Never diagnose based solely on rating scale scores without clinical interview and multi-informant data. 3 Rating scales systematically collect information but do not diagnose ADHD by themselves 3.
• Never diagnose without documenting impairment in multiple settings. 2, 3 Single-setting symptoms suggest environmental factors 1.
• Never skip comorbidity screening. 2, 3 Comorbid conditions are the rule rather than the exception and fundamentally change treatment planning 3.
• Never rely on neuropsychological testing for diagnosis. 1 While it may clarify learning strengths and weaknesses, it does not improve diagnostic accuracy for ADHD 1.

Adults Presenting for First-Time Diagnosis

Adults are more likely to present with predominantly inattentive symptoms rather than hyperactivity 1. You must establish that symptoms were present before age 12, even if the patient was never formally diagnosed as a child 2. Use the ASRS-V1.1 as your initial screening tool, then proceed with comprehensive evaluation including collateral information from family members who knew the patient during childhood 1, 2.