What are the symptoms of Attention Deficit Hyperactivity Disorder (ADHD) in individuals with Intellectual Developmental Disorder (IDD) and what scales are used to assess them?

ADHD Symptoms in Intellectual Developmental Disorder (IDD) and Assessment Scales

ADHD symptoms in individuals with IDD present differently than in the general population, with inattentive symptoms persisting longer into adolescence and requiring specialized assessment tools for accurate diagnosis. 1

Presentation of ADHD in IDD

Core Symptoms

• Inattention symptoms: Unlike typically developing children, these do not decrease during teen years in individuals with IDD 1
• Hyperactivity symptoms: More prominent in early development, similar to typically developing children 1
• Impulsivity: Often manifests as grabbing, pinching, and difficulty waiting 1

Associated Features in IDD

• Higher sensitivity to environmental changes and routine disruptions 1
• Increased risk of being bullied compared to peers without ADHD 1
• Greater difficulty with adaptive functioning 1
• More pronounced emotional dysregulation 1
• Sleep disturbances (2.8 times more likely than typically developing youth) 1

Genetic Syndrome-Specific Presentations

• Deletion 22q11.2: ADHD is a common feature alongside emotional dysregulation and higher verbal than performance IQ 1
• Other genetic syndromes: May have specific behavioral phenotypes that include ADHD-like symptoms 1

Diagnostic Challenges

• Clinical opinion often outperforms standard DSM criteria in diagnosing ADHD in IDD populations 2
• Diagnostic overshadowing can occur (attributing ADHD symptoms to the IDD itself) 1
• Symptoms must be excessive for developmental level, not just chronological age 1
• Difficulty distinguishing between symptoms of ADHD and behaviors related to IDD 2
• Communication limitations may impede self-reporting of symptoms 1

Assessment Scales Used in Studies

Primary Assessment Tools

1. Rating scales from multiple informants: Essential for accurate diagnosis 3

   • Must be collected from at least 2 sources (parents/caregivers, teachers) 3
   • Self-report when age-appropriate and cognitively possible 3

2. DSM-5 based rating scales: Standard but may need adaptation for IDD 3, 2

   • Sensitivity of standard DSM criteria alone is only 0.23 in IDD populations 2

3. Specific scales frequently used:

   • Conners' Rating Scales: Both parent (CPRS) and teacher (CTRS) versions 4, 5
   • ADHD Rating Scale: Good predictor of clinical diagnosis 5
   • Child Behavior Checklist (CBCL): Assesses broader behavioral issues 4
   • Continuous Performance Tests (CPT): Measures sustained attention 4
   • Test of Variables of Attention (TOVA): Assesses attention objectively 4

Developmental Screening Tools

• Ages and Stages Questionnaire (ASQ-III): For ages 1-66 months 1

  • 30-item age-specific parent report measure
  • High test-retest reliability (0.92) and interrater reliability (0.93)
  • Sensitivity 0.83-0.89, Specificity 0.80-0.92

• Parents' Evaluation of Developmental Status (PEDS): For ages 1-95 months 1

  • 10-item parent report measure
  • Sensitivity 0.74-0.79, Specificity 0.70-0.80

Emerging Assessment Approaches

• Three-question screening tool with 88% sensitivity and 87% specificity (needs further validation) 6
• Structured interviews adapted for IDD populations 1

Treatment Considerations

• Stimulants (methylphenidate) show efficacy but with lower effect sizes (0.39-0.52) compared to typically developing children (0.8-0.9) 1
• Risperidone has shown efficacy for hyperactivity as a secondary outcome in IDD populations 1
• Atomoxetine may be considered as an alternative treatment 7

Clinical Approach to Assessment

1. Gather information from multiple sources:

   • Knowledgeable informants across different settings 1
   • Observe behavior directly during assessment 1
   • Compare current behavior to the individual's baseline 1

2. Adapt interview techniques:

   • Simplify questions for the individual with IDD 1
   • Allow extra processing time 1
   • Avoid leading questions and monitor for comprehension 1
   • Watch for echolalia (repeating interviewer's words) 1

3. Consider environmental factors:

   • Assess educational placement appropriateness 1
   • Evaluate recent changes in routine or residence 1
   • Screen for stressful life events 1

4. Rule out alternative explanations:

   • Medical conditions that may mimic ADHD symptoms 3
   • Effects of medications 1
   • Sleep disorders 1
   • Sensory processing issues 1

Common Pitfalls to Avoid

• Using chronological age rather than developmental level to assess symptom appropriateness 1
• Relying solely on DSM criteria without clinical judgment 2
• Failing to assess for co-occurring conditions (anxiety, depression, autism) 3
• Not considering the impact of environmental demands exceeding cognitive abilities 1
• Inadequate collection of information from multiple settings 3
• Overlooking the need for reassessment as developmental status changes 1

The accurate diagnosis and assessment of ADHD in IDD requires specialized knowledge, adapted assessment tools, and careful clinical judgment that considers the individual's developmental level rather than chronological age.