How is attention-deficit/hyperactivity disorder diagnosed in adults?

Diagnosing Adult ADHD

Use the Adult ADHD Self-Report Scale (ASRS-V1.1) Part A as your initial screening tool; a positive screen (4 or more items marked "often" or "very often" out of 6 questions) triggers a comprehensive diagnostic evaluation that must establish at least 5 symptoms from either inattention or hyperactivity-impulsivity categories, symptom onset before age 12, functional impairment in at least 2 settings, and systematic exclusion of mimicking conditions through collateral informants. 1, 2, 3

Step 1: Initial Screening

• Begin with ASRS-V1.1 Part A, which asks patients to rate the frequency of 6 key symptoms 1
• A screen is positive when the patient endorses "often" or "very often" for 4 or more of the 6 questions 1
• If the screen is positive, complete ASRS Part B to further characterize the symptom profile 2

Step 2: Establish DSM-5 Diagnostic Criteria

Symptom Count Requirements

• Adults require at least 5 symptoms from either the inattentive category OR the hyperactivity-impulsivity category (or both for combined presentation) 2, 3
• Symptoms must have persisted for at least 6 months 2
• Inattentive symptoms include: poor attention to detail, difficulty sustaining attention, appearing preoccupied, difficulty completing tasks, organizational challenges, reluctance to engage in sustained mental effort 1
• Hyperactive-impulsive symptoms include: frequent fidgeting, difficulty sitting still, inner restlessness, being loud/disruptive, always "on the go," talking excessively 1

Age of Onset (Non-Negotiable)

• Several symptoms must have been present before age 12—this is mandatory and cannot be waived 1, 2, 3
• Obtain a detailed developmental history focusing on elementary and middle school years 3
• Review old report cards, school records, or prior evaluations when available 3
• Use collateral history from parents, earlier teachers, or siblings when retrospective data are limited 2, 3, 4

Cross-Situational Impairment (Mandatory)

• Document functional impairment in at least 2 independent settings (work, home, social relationships, academic environments) 2, 3, 5
• Gather information from multiple informants: family members, partners, close friends, employers, or colleagues 3, 4
• Critical pitfall: Symptoms reported in only one setting often reflect situational problems rather than true ADHD 5

Step 3: Obtain Collateral Information

• Collateral information from someone who knows the patient well is mandatory, not optional 2, 3, 4
• Self-report alone is insufficient because adults often minimize symptoms 3
• Use standardized rating scales such as the Conners Adult ADHD Rating Scales (CAARS) for comprehensive assessment, though these do not diagnose ADHD by themselves 3, 6
• Self-report and collateral reports of symptoms are highly correlated, but probands typically report more inattentive symptoms than collaterals 7

Step 4: Systematic Exclusion of Alternative Diagnoses

Mandatory Differential Diagnoses to Rule Out

• Substance use disorders: Marijuana and stimulants produce identical symptoms to ADHD 3
  • Reassess after sustained abstinence from substance use 3
• Trauma and PTSD: Can cause hypervigilance, concentration problems, and emotional dysregulation 3
  • Treat PTSD before reassessing attention symptoms 3
• Mood disorders: Depression and anxiety can mimic inattention and restlessness 1, 3, 8
  • Optimize treatment for mood and anxiety symptoms before diagnosing ADHD 3
• Other psychiatric conditions: Psychotic disorders, dissociative disorders, personality disorders (especially borderline and antisocial) 1, 9, 8

Common Mimicking Conditions

• Sleep disorders (restless leg syndrome, hypersomnolence) can mimic ADHD but are not diagnostic criteria 5, 8
• Oppositional or defiant behavior suggests Oppositional Defiant Disorder, not ADHD, though they may co-occur 1, 5
• Symptoms must not be better explained by oppositional behavior, defiance, hostility, or failure to understand tasks 1, 2

Step 5: Screen for Comorbidities

• Approximately 80% of adults with ADHD have at least one comorbid psychiatric disorder 8
• Mandatory screening for: 3, 8
  • Anxiety disorders and depression (highly comorbid)
  • Substance use disorders (alcohol, marijuana, stimulants)
  • Mood disorders (unipolar or bipolar)
  • Personality disorders (borderline, antisocial)
  • Sleep disorders
• Around 10% of adults with recurrent depression/anxiety have ADHD, and treating depression/anxiety alone will likely be inadequate without addressing ADHD 1

Step 6: Document Functional Impairment

• Clear evidence that symptoms interfere with or reduce quality of functioning in interpersonal, academic, or occupational domains is required 2
• Assess for: academic underachievement, job instability, relationship problems, financial difficulties, legal issues 9, 8
• The ability to consistently complete tasks contradicts the core ADHD symptom of inattention and suggests absence of significant functional impairment 5

Critical Diagnostic Pitfalls to Avoid

• Relying solely on self-report without collateral information 3
• Not establishing childhood onset before age 12—this is non-negotiable 3
• Diagnosing ADHD when symptoms are better explained by substance use, trauma, or mood disorders 3
• Using rating scale scores alone without comprehensive clinical interview 3, 4
• Failing to gather sufficient information from multiple settings before concluding criteria are not met 5
• Not recognizing that some adolescents may feign symptoms to obtain stimulant medication 2

When to Refer to a Specialist

• Refer to a psychiatrist, developmental-behavioral specialist, or neuropsychologist when: 3
  • The clinical picture is complex, atypical, or involves significant comorbidity
  • Complex comorbidity requires specialized medication management
  • Diagnostic uncertainty persists after comprehensive evaluation

Unspecified ADHD Diagnosis

• Use the unspecified ADHD diagnosis when ADHD symptoms cause clinically significant impairment but you cannot establish that full DSM-5 criteria are met, typically due to insufficient information from multiple settings or inability to confirm symptom onset before age 12 5
• Parent training in behavior management (PTBM) is beneficial even when full diagnostic criteria are not met 5