Diagnostic Criteria: Attention-Deficit/Hyperactivity Disorder in ICD-11

Introduction

Standardized diagnostic criteria are essential tools to ensure accuracy, consistency, and effective communication among mental health professionals. In the case of ADHD, a correct diagnosis allows for early interventions that can transform life trajectories, reducing academic, occupational, and social impairments. This guide presents ICD-11 criteria in an objective manner, facilitating their application in daily clinical practice.

General Criteria (6A05)

Criterion A: Persistent Pattern of Inattention and/or Hyperactivity-Impulsivity

ADHD is characterized by a persistent and pervasive pattern of symptoms of inattention and/or hyperactivity-impulsivity that directly impact functioning across multiple contexts. Inattention manifests as difficulty maintaining focus, excessive distractibility, frequent forgetfulness, and disorganization. Hyperactivity presents as motor restlessness, inability to remain seated, and internal feelings of agitation. Impulsivity is characterized by difficulty waiting, frequent interruptions, and hasty decision-making. These symptoms must be present for at least 6 months, be inconsistent with the expected developmental level, and cause significant functional impairment in academic, occupational, or social activities.

Criterion B: Early Onset and Persistence

Symptoms must have onset in childhood or adolescence, typically before age 12, although diagnosis may be established later when there is clear retrospective evidence. It is essential to document that symptoms are not recent or situational, but represent a chronic pattern of functioning. Assessment should include detailed history, preferably with information from multiple sources (parents, teachers, spouses), old school report cards, and reports of childhood behavior. Symptoms often persist into adulthood, although they may manifest differently with age. Motor hyperactivity may decrease, being replaced by internal restlessness, while organizational and planning problems become more evident.

Criterion C: Exclusions

Differentiate from:

• Neurodevelopmental Disorders: Intellectual disability and Autism Spectrum Disorder may present with inattention, but with distinct characteristics
• Mood Disorders: Depressive or manic episodes cause secondary inattention due to affective state
• Anxiety Disorders: Excessive worry may mimic inattention
• Substance Use Disorders: Intoxication or withdrawal may produce similar symptoms
• Medical Conditions: Hypothyroidism, sleep apnea, nutritional deficiencies must be excluded

Specifiers and Subtypes

6A05.0: Attention-Deficit/Hyperactivity Disorder, Predominantly Inattentive Presentation

Specific criteria:

• Predominant inattention symptoms: At least 6 symptoms of inattention (5 for adults) present persistently
• Minimal hyperactivity-impulsivity symptoms: Fewer than 6 symptoms of hyperactivity-impulsivity (fewer than 5 for adults)
• Clinical manifestations: Difficulty following instructions, frequent loss of objects, forgetfulness in daily activities, avoidance of tasks requiring sustained mental effort, chronic disorganization, easily distracted by external stimuli or internal thoughts

6A05.1: Attention-Deficit/Hyperactivity Disorder, Predominantly Hyperactive-Impulsive Presentation

Specific criteria:

• Predominant hyperactivity-impulsivity symptoms: At least 6 symptoms of hyperactivity-impulsivity (5 for adults) present persistently
• Minimal inattention symptoms: Fewer than 6 symptoms of inattention (fewer than 5 for adults)
• Clinical manifestations: Constant motor restlessness, difficulty remaining seated, excessive talking, frequent interruptions, difficulty waiting turns, intruding on others' activities, impulsive decision-making without considering consequences

6A05.2: Attention-Deficit/Hyperactivity Disorder, Combined Presentation

Specific criteria:

• Symptoms in both domains: At least 6 symptoms of inattention AND 6 symptoms of hyperactivity-impulsivity (5 of each for adults)
• Impairment in multiple areas: Significant functional impact related to both inattention and hyperactivity-impulsivity
• Clinical manifestations: Combination of symptoms from the two previous presentations, usually with greater severity and overall functional impairment

Quick Decision Table

| If present | And also | But NOT | Code | |-------------|----------|---------|--------| | ≥6 inattention symptoms | Onset before age 12 | Symptoms only during depressive episode | 6A05.0 | | ≥6 hyperactivity symptoms | Impairment in 2+ contexts | Recent stimulant use | 6A05.1 | | ≥6 inattention + ≥6 hyperactivity | Duration ≥6 months | Better explained by ASD | 6A05.2 | | Significant symptoms | Documented childhood history | Only during sleep deprivation | 6A05 (specify) |

Diagnostic Algorithm

    Symptoms of inattention and/or
    hyperactivity-impulsivity?
              │
         ┌────┴────┐
        YES       NO → Not ADHD
         │
    Onset before
    age 12?
         │
    ┌────┴────┐
   YES       NO → Investigate other disorders
    │
Impairment in 2+
  contexts?
    │
┌───┴───┐
YES    NO → Subclinical symptoms
 │
Better explained
by another condition?
 │
┌───┴───┐
NO     YES → Alternative diagnosis
 │
Quantify symptoms:
 │
├─ ≥6 inattention, <6 hyper/imp → [6A05.0](/en/code/6A05.0)
├─ <6 inattention, ≥6 hyper/imp → [6A05.1](/en/code/6A05.1)
└─ ≥6 inattention, ≥6 hyper/imp → [6A05.2](/en/code/6A05.2)

Practical Cases

Case 1: 9-year-old boy brought by parents for school complaints. Teacher reports that he "lives in his own world," does not complete activities, constantly loses materials. At home, he forgets tasks and requires constant supervision. Report cards since age 6 show comments about inattention. Does not present excessive motor restlessness. Typical neuropsychomotor development, no comorbidities.

• Diagnosis: 6A05.0 (Predominantly Inattentive Presentation)
• Justification: At least 6 persistent inattention symptoms for more than 3 years, onset before age 12, impairment in school and home contexts, absence of significant hyperactivity-impulsivity symptoms

Case 2: 28-year-old woman seeks evaluation for occupational difficulties. Reports always having been "electric," talks a lot, interrupts conversations, acts impulsively. In childhood, was described as "never sits still." Currently, constant internal restlessness, difficulty in long meetings, impulsive decisions. Attention relatively preserved in tasks of interest.

• Diagnosis: 6A05.1 (Predominantly Hyperactive-Impulsive Presentation)
• Justification: At least 5 hyperactivity-impulsivity symptoms (adult criterion), documented childhood onset, occupational and social impairment, inattention symptoms below diagnostic threshold

Case 3: 14-year-old adolescent with history of school difficulties since early literacy. Marked inattention, chronic disorganization, does not complete tasks. Also presents constant restlessness, frequently gets up in class, talks excessively, acts without thinking. Multiple report cards document both difficulties.

• Diagnosis: 6A05.2 (Combined Presentation)
• Justification: Full criteria for both inattention AND hyperactivity-impulsivity, documented early onset, significant functional impairment in multiple areas

Clinician's Checklist

• [ ] Assess at least 6 inattention symptoms (or 5 if ≥17 years): careless mistakes, difficulty sustaining attention, appears not to listen, fails to follow through on instructions, difficulty organizing, avoids tasks requiring sustained mental effort, loses necessary objects, easily distracted, forgetfulness in daily activities
• [ ] Assess at least 6 hyperactivity-impulsivity symptoms (or 5 if ≥17 years): fidgets with hands/feet, leaves seat inappropriately, runs/climbs excessively, unable to play quietly, "on the go," talks excessively, blurts out answers, difficulty waiting turns, interrupts/intrudes
• [ ] Confirm onset before age 12 with objective evidence (report cards, family reports, medical records)
• [ ] Document functional impairment in 2+ contexts (home, school/work, social) through multiple sources of information
• [ ] Exclude differential diagnoses (mood disorders, anxiety, ASD, intellectual disability, substance use, medical conditions)
• [ ] Investigate common comorbidities (oppositional defiant disorder, conduct disorder, anxiety disorders, learning disorders, sleep disorders)
• [ ] Apply standardized instruments when possible (SNAP-IV scales, ASRS for adults, questionnaires for parents and teachers)
• [ ] Perform basic physical examination and request complementary tests if indicated (TSH, complete blood count, polysomnography if sleep apnea suspected)

References

• WHO ICD-11 2024 - International Classification of Diseases, 11th Revision
• American Psychiatric Association (2022). DSM-5-TR: Diagnostic and Statistical Manual of Mental Disorders
• Faraone SV, et al. (2021). The World Federation of ADHD International Consensus Statement: 208 Evidence-based conclusions about the disorder. Neuroscience & Biobehavioral Reviews
• National Institute for Health and Care Excellence (2019). Attention deficit hyperactivity disorder: diagnosis and management. NICE guideline [NG87]

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Important Notes:

• This guide is an auxiliary tool and does not replace experienced clinical judgment
• Assessment should be comprehensive, considering cultural and individual context
• Careful documentation is essential for accurate diagnosis and appropriate follow-up
• Periodic reassessments are recommended, as presentations may change over time