What is the best way to diagnose Attention Deficit Hyperactivity Disorder (ADHD) in adults?

Diagnosing ADHD in Adults

The best way to diagnose ADHD in adults requires a comprehensive psychiatric evaluation with particular focus on documenting core ADHD symptoms that started in childhood (before age 12), combined with structured rating scales, collateral information from family or significant others, and systematic screening for comorbid conditions and substance use. 1

Core Diagnostic Requirements

Clinical Interview Components

The diagnostic process must establish several critical elements through direct clinical interview 1:

• Childhood onset documentation: Confirm that ADHD symptoms were present before age 12 years, as this is required by DSM-5 criteria 1
• Current symptom assessment: Evaluate for at least 5 symptoms of inattention and/or hyperactivity-impulsivity that have persisted for at least 6 months in adults (6 symptoms required for those under age 17) 1
• Cross-situational impairment: Document that symptoms cause functional impairment in at least 2 settings (work, home, social relationships) 1
• Substance use history: Obtain detailed drug and alcohol history, as comorbid substance abuse is highly prevalent; consider urine drug screening 1

Collateral Information is Essential

Adults with ADHD often have notoriously poor insight and underestimate the severity of their symptoms and resulting impairments 1. Therefore:

• Obtain information from spouse, significant other, parent, or close friend 1
• Review childhood school records when available 2
• Gather workplace performance information if accessible 2

Structured Rating Scales

Use validated screening and diagnostic tools to supplement clinical interview 1, 3:

• Adult ADHD Self-Report Scale (ASRS-V1.1): Part A screens positive when patient endorses "often" or "very often" for 4 or more of 6 questions 1
• Wender Utah Rating Scale: Assesses retrospective childhood symptoms 1
• Brown Attention-Deficit Disorder Scale for Adults 1
• Conners Adult ADHD Rating Scales 1, 3

These scales can be completed in 3-5 minutes and provide standardized symptom assessment 2.

Medical Evaluation

Conduct focused medical assessment to rule out conditions that mimic ADHD 1:

• Medical history and physical examination: Screen for thyroid disorders, sleep disorders, neurological conditions 1
• Screening laboratory tests: Basic metabolic panel, thyroid function as clinically indicated 1
• Sleep evaluation: Sleep apnea and other sleep disorders commonly present with attention problems 1

Differential Diagnosis and Comorbidity Screening

This is a critical step that cannot be skipped. Systematically evaluate for conditions that overlap with or commonly co-occur with ADHD 1:

Psychiatric Conditions to Rule Out or Identify:

• Mood disorders: Bipolar disorder and major depression can mimic ADHD symptoms 1
• Anxiety disorders: Generalized anxiety, social phobia 1
• Substance use disorders: Active use can mimic or exacerbate ADHD symptoms 1, 3
• Personality disorders: Particularly borderline and antisocial patterns 1
• Trauma/PTSD: Can present with attention and impulse control problems 1

Other Conditions:

• Learning disabilities: May coexist or be misattributed as ADHD 1
• Narcolepsy: Excessive daytime sleepiness affects attention 1
• Borderline intellectual functioning: Undiagnosed cognitive limitations 1

Common Diagnostic Pitfalls

Beware of these scenarios that complicate diagnosis 1, 3:

• Substance effects: Marijuana and other substances can produce symptoms identical to ADHD 1
• Malingering for stimulants: Some adults feign symptoms to obtain performance-enhancing medications 1, 3
• Depression/anxiety masquerading as ADHD: Approximately 10% of adults with recurrent depression/anxiety actually have underlying ADHD 1
• Late presentation without childhood documentation: DSM-5 requires evidence of symptoms before age 12, which can be challenging to establish retrospectively 1

Diagnostic Algorithm

Follow this sequence 1, 3, 2:

1. Initial screening: Administer ASRS-V1.1 Part A (positive if ≥4 of 6 items endorsed as "often/very often") 1
2. Comprehensive clinical interview: Document childhood-onset symptoms, current symptoms, and cross-situational impairment 1
3. Collateral information: Interview family member or significant other 1
4. Structured rating scales: Complete full ADHD symptom inventories 1
5. Comorbidity screening: Systematically evaluate for mood, anxiety, substance use, and other psychiatric conditions 1
6. Medical screening: Rule out medical mimics through history, exam, and selective laboratory testing 1
7. Functional impairment assessment: Document specific impairments in work, relationships, and daily functioning 1

When to Refer

Consider referral to psychiatry or psychology when 1:

• Diagnostic uncertainty persists after initial evaluation
• Complex comorbid psychiatric conditions are present
• Neuropsychological testing is needed to clarify learning disabilities
• Patient has active substance use disorder requiring specialized treatment
• Safety concerns exist (suicidal ideation, severe impulsivity)

The diagnosis relies fundamentally on classical psychiatric skills: careful clinical interview, behavioral observation, and integration of multiple information sources—not on laboratory tests or neuroimaging 1.