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Intellectual Developmental Disorder and Autism Spectrum Disorder���Considerations for differential and dual diagnosis

Nicole Kesner, PhD | Autism & Neuropsychology Postdoctoral Fellow

Oregon Health & Science University | Child Development and Rehabilitation Center

02/13/2025

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Agenda

  • Review diagnostic criteria for ID and ASD�
  • Domain-specific presentations of ID and ASD
    • Cognition
    • Adaptive Functioning
    • Social Communication
    • Restricted and Repetitive Behaviors�
  • Considerations for dual diagnosis

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Intellectual Developmental Disorder (intellectual Disability)

Onset in developmental period

Includes both intellectual and adaptive functioning deficits

    • Intellectual: reasoning, problem-solving, planning, abstract thinking, judgment, academic learning, and learning from experience)
    • Adaptive: developmental and sociocultural standards for personal independence and social responsibility

Severity levels (mild, moderate, severe, profound)

Confirmed by clinical assessment and standardized intelligence testing

APA (2022)

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Autism Spectrum Disorder

  • Persistent deficits in social communication and interaction (3/3)
    • Social-emotional reciprocity (initiation and responsiveness)
    • Nonverbal communication (integration of verbal and nonverbal communication, gesture use, facial expressions)
    • Development and maintenance of social relationships

APA (2022)

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Autism Spectrum Disorder

  • Persistent deficits in social communication and interaction (3/3)
    • Social-emotional reciprocity (initiation and responsiveness)
    • Nonverbal communication (integration of verbal and nonverbal communication, gesture use, facial expressions)
    • Development and maintenance of social relationships
  • Restricted, repetitive patterns of behavior, interests, or activities (2/4)
    • Stereotyped or repetitive motor movements, object use, or speech
    • Insistence on sameness, routinized behavior
    • Highly restricted, fixated interests
    • Hyper- or hyporeactivity to sensory input or mutual sensory interests

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APA (2022)

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Cognition

  • ~30-70% of individuals with ASD have an ID, and 40% of individuals with severe ID meet criteria for ASD (Cervantes & Matson, 2015; Hossain et al., 2020))

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Cognition

  • ~30-70% of individuals with ASD have an ID, and 40% of individuals with severe ID meet criteria for ASD (Cervantes & Matson, 2015; Hossain et al., 2020)

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Adaptive Functioning

ASD

  • Variable profile
  • Daily living skills > communication > socialization
  • Cognitive > adaptive in those without ID
    • Gap increases with age
  • Adaptive > cognitive in those with lower IQ
  • Impact of comorbidities

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Matthews et al. (2015)

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Adaptive Functioning

ASD

  • Variable profile
  • Daily living skills > communication > socialization
  • Cognitive > adaptive in those without ID
    • Gap increases with age
  • Adaptive > cognitive in those with lower IQ
  • Impact of comorbidities

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ID

  • Homogeneous profile across conceptual, practical, and social domains
  • Socially-oriented adaptive skills
    • Expressing oneself
    • Interactions with others
    • Play and leisure skills

Matthews et al. (2015)

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Social Communication

Jordan (2019)

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Social Communication

ASD

  • Core feature of diagnosis (observations in infancy)
  • Stereotyped language
  • Poor integration of verbal and nonverbal communication
  • Inflexible play
  • Difficulties consistent across settings
  • Discrepancy from other functional domains
  • Limited joint attention

Saulnier & Ventola (2012)

Jordan (2019)

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Social Communication

ID

  • Pragmatic and grammatical errors – consistent with developmental level)
  • Can compensate with use of nonverbal communication
  • Tangential or irrelevant social responses
  • Curious in play and attempts to involve caregivers
  • Difficulties more pronounced with same-aged peers
  • Limited joint attention

ASD

  • Core feature of diagnosis (observations in infancy)
  • Stereotyped language
  • Poor integration of verbal and nonverbal communication
  • Inflexible play
  • Difficulties consistent across settings
  • Discrepancy from other functional domains
  • Limited joint attention

Saulnier & Ventola (2012)

Jordan (2019)

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Restricted and Repetitive Behaviors

  • Greater reductions in functional independence in ASD
  • Mild-moderate ID – immature interests relative to developmental level
  • Hyper and hypo-sensitivity more common in ASD + ID than ID alone
  • Children with ID may demonstrate more RRBs than TD children

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Considerations for dual diagnosis

ID and ASD are not mutually exclusive

Diagnosis of ASD + ID when social communication and interaction are significantly impaired relative to the developmental of the individual’s nonverbal reasoning skills.

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Considerations for dual diagnosis

Child's mental age (through IQ and adaptive assessment)

3-4-years: can talk about past and future events, request, give information when asked, initiate conversations

6-years: use of metaphors/sarcasm/non-literal language, understanding needs of listener in conversations

RRBs: toddlers and young children often jump up and down and clap their hands repeatedly, insist on routines

Are the patient’s social-communication skills delayed compared to their mental age?

Lecavalier et al. (2022)

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Considerations for dual diagnosis

  • It may not be possible to judge presence/absence of symptoms if child has not achieved certain developmental skills (e.g., severe ID)�
  • Consider developmental trajectory
    • Have social communication delays always been commensurate with other developmental areas?
    • Have there been time where social communication delays have been more isolated or significant?
    • Unlikely for sudden manifestation of social communication deficits and RRBs to suddenly manifest�
  • Are social communication difficulties a reflection of social immaturity?�
  • What is the level of accommodation needed?�
  • Multidisciplinary evaluations

Lecavalier et al. (2022)

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Thank you