Clinical Anxiety Scale for People with Intellectual Disabilities

1. Abstract

The Clinical Anxiety Scale for People with Intellectual Disabilities (ClASP-ID) is a specialized, informant-report psychometric instrument engineered to evaluate and differentiate symptoms of anxiety in individuals with mild to profound intellectual disabilities, including those co-diagnosed with autism spectrum disorder. Developed by Jessica Eliza Mingins and colleagues (2024), the ClASP-ID directly addresses the pervasive clinical challenge of diagnostic overshadowing, behavioral masking, and symptom overlap among affective disturbances, physical distress, and baseline neurodevelopmental topographies. The instrument comprises 33 operationalized behavioral items structured across four empirically derived dimensions: Anxiety (13 items), Pain (9 items), Low Energy/Withdrawal (6 items), and Consolability (4 items). Items are rated by parents, familial caregivers, or support professionals on an anchor-defined seven-point Likert scale (ranging from 0 to 6, calibrated across behavioral frequency over the preceding month).

Psychometric evaluation of the ClASP-ID across large-scale neurodevelopmental cohorts demonstrated robust dimensional integrity, exceptional internal consistency (Cronbach’s alpha ranging from .80 to .92 across clinical subscales; total scale alpha > .90), excellent inter-rater reliability, and stability across test-retest intervals. Exploratory and confirmatory factor analyses verified that distinguishing non-verbal physiological markers of somatic pain and vegetative features of depressive affect from core cognitive-behavioral manifestations of autonomic anxiety significantly elevates diagnostic precision. Convergent validity is confirmed via substantial correlations with standardized legacy measures of emotional dysregulation and challenging behavior, while discriminant validity demonstrates its capacity to untangle idiopathic anxiety from co-occurring medical discomfort. Consequently, the ClASP-ID functions as an indispensable clinical assessment battery and research tool within neurodevelopmental psychiatry, pediatric neuropsychology, and specialized intellectual and developmental disability services.

2. Keywords

Clinical Anxiety Scale for People with Intellectual Disabilities, ClASP-ID, Intellectual Disability, Autism Spectrum Disorder, Psychometrics, Diagnostic Overshadowing, Behavioral Equivalents, Informant Report, Neurodevelopmental Disorders, Anxiety Assessment, Factor Analysis, Somatic Discomfort.

3. Authors

The Clinical Anxiety Scale for People with Intellectual Disabilities was conceptualized, operationalized, and psychometrically validated by a multi-institutional consortium of neurodevelopmental psychologists and behavioral clinical scientists:

• Jessica Eliza Mingins, Ph.D. — School of Psychology, College of Health and Life Sciences, Aston University, Birmingham, United Kingdom; Cerebra Centre for Neurodevelopmental Disorders, School of Psychology, University of Birmingham, Birmingham, United Kingdom.
• Joanne Tarver, Ph.D. — Department of Psychology, School of Life and Health Sciences, Aston University, Birmingham, United Kingdom.
• Effie Pearson, Ph.D. — Cerebra Centre for Neurodevelopmental Disorders, School of Psychology, University of Birmingham, Birmingham, United Kingdom.
• Georgina Edwards, M.Sc. — Cerebra Centre for Neurodevelopmental Disorders, School of Psychology, University of Birmingham, Birmingham, United Kingdom.
• Megan Bird, M.Sc. — Cerebra Centre for Neurodevelopmental Disorders, School of Psychology, University of Birmingham, Birmingham, United Kingdom.
• Hayley Crawford, Ph.D. — Warwick Medical School, University of Warwick, Coventry, United Kingdom.
• Chris Oliver, Ph.D. — Cerebra Centre for Neurodevelopmental Disorders, School of Psychology, University of Birmingham, Birmingham, United Kingdom.
• Lauren Shelley, Ph.D. — Cerebra Centre for Neurodevelopmental Disorders, School of Psychology, University of Birmingham, Birmingham, United Kingdom.
• Jane Waite, Ph.D. — School of Psychology, College of Health and Life Sciences, Aston University, Birmingham, United Kingdom (Principal Investigator and Corresponding Author).

4. Purpose

The primary clinical and psychometric imperative underlying the creation of the Clinical Anxiety Scale for People with Intellectual Disabilities (ClASP-ID) is the urgent necessity to identify, monitor, and remediate internalizing disorders in populations exhibiting compromised expressive communication. Anxiety disorders are disproportionately prevalent among individuals with intellectual disability (ID) and comorbid autism spectrum conditions, exhibiting point prevalence estimates substantially higher than those observed in neurotypical peer groups. Despite this profound vulnerability, clinical identification remains exceedingly deficient.

Historically, the detection of subjective affective states such as anticipatory apprehension, catastrophic rumination, and autonomic hyperarousal has depended almost entirely upon introspective linguistic self-report instruments. In individuals characterized by profound verbal impairments, receptive communicative deficits, or cognitive developmental delay, conventional psychometric assessment tools collapse. In response, clinicians frequently succumb to diagnostic overshadowing—a cognitive bias wherein overt affective, agitated, or distressed behaviors are erroneously attributed entirely to the baseline intellectual impairment or autistic phenotype rather than to a treatable secondary psychiatric disorder.

Furthermore, behavioral manifestations of physical pain (e.g., gastrointestinal distress, dental disease, musculoskeletal spasms) and clinical depression (e.g., psychomotor retardation, vegetative withdrawal) share significant phenotypic overlap with primary anxiety. A non-verbal individual exhibiting motor pacing, facial grimacing, or social avoidance may be experiencing severe dental pain, a major depressive episode, or panicogenic environmental distress. Standard generalized behavior problem checklists lack the diagnostic granularity necessary to differentiate these etiologies. Consequently, individuals are at heightened risk of either receiving inappropriate psychotropic pharmacotherapy (e.g., antipsychotics prescribed for behavioral suppression) or being denied essential medical, environmental, or psychological interventions.

The ClASP-ID was systematically engineered to bridge this diagnostic abyss. Its clinical and research applications encompass:

• Differential Phenotypic Disentanglement: Explicitly isolating core anxiety behaviors from observable behavioral markers of physical pain and low mood/vegetative withdrawal.
• Objective Baseline and Treatment Trajectory Monitoring: Offering an empirically grounded, fine-grained seven-point metric sensitive to behavioral titration, therapeutic response, cognitive-behavioral environmental modifications, and psychopharmacological interventions.
• Longitudinal Cohort Phenotyping: Enabling academic researchers in psychiatric genetics and neurodevelopmental syndromes (e.g., Fragile X syndrome, Cornelia de Lange syndrome, Angelman syndrome, Tuberous Sclerosis Complex) to map the natural history and neurobiological correlates of anxiety.
• Functional Behavioral Assessments: Informing clinical behavior analysts and multidisciplinary disability support teams regarding the emotional antecedents and internal contextual variables precipitating severe behaviors of concern, such as self-injurious behavior (SIB) or aggression.

5. Psychological Construct

The ClASP-ID conceptualizes anxiety not as an inaccessible, purely private introspective event, but as a composite multi-systemic construct expressed via motoric, observable physiological, behavioral-avoidant, and interpersonal topographies. Because these manifestations interact continuously with other physiological and affective drivers, the ClASP-ID operationalizes the target domain across four interconnected, clinically vital subscales:

1. Core Anxiety

The Anxiety subscale captures observable hyperarousal, observable apprehension, behavioral avoidance, vigilance, and environmental disruption attributable to acute emotional distress. Rather than demanding cognitive introspection regarding abstract fear, this subscale captures concrete, externally observable behavioral indices. Typical topographies include:

• Facial and Skeletal Hypertonia: Sustained tense facial expressions, angry or strained appearances under ambient stimulation, and generalized muscular rigidity.
• Motoric Agitation and Restlessness: Continuous, non-goal-directed motor activity, pacing across rooms, and inability to maintain somatic stillness.
• Active and Passive Avoidance: Active physical flight from novel or conditioned aversive settings, hiding behind furniture, or erecting sensory or physical barriers (such as pulling blankets overhead or barricading oneself) to isolate against environmental stimuli.
• Freezing and Tonic Immobility: Sudden, abrupt cessation of motor activity (freezing to the spot) in direct response to environmental transitions or anxiety-provoking encounters.
• Vocal Dysregulation: Paralinguistic markers of fear and frustration, encompassing whining, grumbling, sudden screaming, or guttural vocal outbursts.
• Systemic Functional Impairment: Pervasive disruption to adaptive family routines, including the complete cancellation of community outings, holidays, or recreational interactions due to catastrophic anticipatory distress.

2. Pain

Physical discomfort is a primary confounding variable in intellectual disability. The Pain subscale systematically captures physiological and protective motor behaviors specifically indicative of somatic or visceral distress. By capturing these indices independently of affective panic, the tool allows clinicians to determine whether agitated presentations stem from medical pathology. Behavioral indices include:

• Guarding and Protective Movements: Sustained manual clutching, touching, or defensive posturing over specific anatomical regions (e.g., holding the abdomen, guarding the jaw, flinching upon approach).
• Autonomic and Involuntary Somatic Signals: Spontaneous sharp gasping, unexpected respiratory intakes, unprovoked lacrimation (watery eyes occurring distinct from emotional crying episodes), and facial lip-pouting or lip-quivering.
• Motor Dysregulation: Onset of jerky movements, tremors, involuntary shivering, altered leg postures (e.g., drawing the lower limbs upward toward the torso), and severe bruxism (repetitive teeth grinding).

3. Low Energy / Withdrawal

This subscale captures the vegetative and motivational sequelae typically associated with depressive phenotypes, emotional exhaustion, or the lethargic manifestations of mood disorders. Differentiating this dimension prevents the misclassification of avolition or anhedonia as quiet, generalized anxiety. Indicators include:

• Avolition and Anhedonia: Complete cessation or marked loss of interest in formerly cherished recreational activities, toys, or daily reinforcers.
• Vegetative Retardation: Pervasive lack of physical vitality, unexplained lethargy, somnolence, prolonged daytime sleep duration, and profound difficulty waking in the morning.
• Social and Affective Disengagement: Withdrawn, emotionally detached, or “vacant” responsiveness; prolonged periods of quiet, isolated self-containment with marked disinterest in environmental engagement.

4. Consolability

The Consolability dimension represents a distinctive structural innovation within psychiatric scale construction for developmental disabilities. It evaluates the contextual plasticity and remediability of the individual’s emotional distress. Individuals with circumscribed anxiety provoked by environmental unpredictability or sensory overload frequently recover baseline equilibrium rapidly when proactive environmental adjustments are deployed. Items evaluate:

• Caregiver Mitigation Efficacy: The degree to which core caregivers can effectively comfort, de-escalate, or soothe the distressed individual via vocal reassuring or physical presence.
• Context-Dependent Relaxation: The restoration of somatic calm when returned to highly familiar, secure, or preferred physical sanctuaries (e.g., their personal bedroom or home environment).
• Stimulus Removal: Immediate therapeutic attenuation of distress precipitated directly by extracting the individual from the triggering setting or eliminating an aversive focal object.
• Proactive Structuring: The clinical efficacy of preparatory schedules, social stories, or behavioral pre-warnings in preventing catastrophic emotional escalation.

6. Theoretical Framework

The structural architecture of the ClASP-ID is anchored in a synthesis of contemporary affective neuroscience, tripartite models of emotion, and applied behavioral analytic frameworks of communicative function in severe neurodevelopmental disorders.

The Tripartite Model of Anxiety and Depression

Historically formulated by Clark and Watson (1991), the tripartite model posits that while anxiety and depression share a broad dimension of general negative affectivity, they are decisively distinguished by unique physiological and behavioral profiles: autonomic hyperarousal is specific to anxiety, whereas low positive affect and anhedonia are specific to depression. In individuals with intellectual disabilities who cannot verbally communicate internal subjective distress, these constructs manifest as divergent external behaviors. The ClASP-ID operationalizes this theoretical distinction by segregating physiological restlessness, autonomic hyperarousal, and avoidant panic (Anxiety) from vegetative lethargy, vacant withdrawal, and loss of interest (Low Energy/Withdrawal).

Neurodevelopmental Behavioral Phenotyping and the “Behavioral Equivalents” Paradigm

The theoretical framework of behavioral equivalents—pioneered in intellectual disability psychiatry by scholars such as Chris Oliver and colleagues—postulates that subjective psychiatric phenomena express themselves via compensatory motor, paralinguistic, and physiological behaviors when cognitive and linguistic faculties are impaired. A catastrophic cognition within neurotypical panics (e.g., “I am having a heart attack”) translates into physiological panic equivalents: paroxysmal freezing, frantic pacing, sensory hiding, or aggressive flight. By isolating these motor topographies through systematic qualitative caregiver interviews and consensus clinician workshops, the ClASP-ID bypasses the reliance on language while remaining theoretically anchored in the neurobiology of anxiety.

Hierarchical Distress Differentiation and Diagnostic Overshadowing

The inclusion of the “Pain” and “Consolability” dimensions within an anxiety inventory is rooted in diagnostic differentiation theory. Somatosensory signaling from medical pathologies mimics panic states via acute sympathetic nervous system excitation (elevated heart rate, tachypnea, facial grimacing, motor restlessness). However, as posited by behavioral ecology models, true psychiatric anxiety displays distinct functional dynamics: it is heavily modulated by environmental antecedents, anticipatory cues, and caregiver soothing (Consolability). Conversely, severe acute pain from occult physical conditions (e.g., gastroesophageal reflux, dental abscesses, otitis media) typically does not yield to psychological pre-warning or situational consolability, and features anatomical guarding. The ClASP-ID integrates these behavioral boundaries directly into its factor structure, offering a theoretically cohesive model that safeguards against diagnostic overshadowing.

7. Validity

The psychometric development of the ClASP-ID adhered to the rigorous evidentiary standards outlined in the Standards for Educational and Psychological Testing (AERA, APA, NCME), demonstrating robust construct, convergent, discriminant, and content validity.

Content and Face Validity

Item generation commenced through exhaustive empirical literature syntheses, deep qualitative investigations, and systematic clinical consensus panels involving specialist clinical psychologists, psychiatrists, learning disability nurses, and familial caregivers. This iterative methodology generated an extensive pool of non-verbal, observable indicators. Items that depended on verbal reflection, assumed high cognitive ability, or exhibited ambiguity across developmental settings were systematically eliminated, yielding an exceptionally robust 33-item clinical measure with high face validity for parents and clinicians alike.

Construct and Factorial Validity

Construct validity was empirically corroborated through structural equation modeling and exploratory-to-confirmatory factor analytic pipelines. The structural separation into four distinct factors confirmed that anxiety within intellectual disabilities does not represent an undifferentiated mass of negative distress, but rather partitions cleanly into autonomic/avoidant anxiety, physical pain topographies, depressive withdrawal, and contextual consolability. Inter-factor correlations were theoretically congruent: the Anxiety factor exhibited moderate, statistically significant positive correlations with Pain and Low Energy/Withdrawal, while maintaining distinct structural divergence.

Convergent Validity

Convergent validity was evaluated by correlating the ClASP-ID Anxiety subscale against established, validated informant-report measures of affective pathology and challenging behavior in intellectual disabilities, such as the Anxiety, Depression And Mood Scale (ADAMS), the Aberrant Behavior Checklist (ABC; specifically the Irritability and Hyperactivity subscales), and the Repetitive Behavior Questionnaire. The ClASP-ID Anxiety factor exhibited strong, statistically significant convergent validity coefficients with established anxiety indices (typically falling within the r = .60 to .78 range, p < .001). Furthermore, associations with severe behavioral disruption indices confirmed clinical observations that acute, unmanaged anxiety frequently functions as an establishing operation for behavioral crises.

Discriminant Validity

Discriminant validity was established through two primary psychometric mechanisms:

• Subscale Divergence: The distinct loading of the Pain subscale demonstrated that somatic indices (e.g., sharp breath intakes, anatomical guarding, isolated limb jerking) maintain low-to-moderate cross-loadings against pure anxiety items, successfully segregating organic discomfort from phobic or generalized anxiety.
• Differential Syndrome Profiles: When administered across distinct genetic syndrome cohorts with established behavioral phenotypes (e.g., populations with elevated physiological pain thresholds vs. populations with high genetic predispositions toward social and generalized anxiety), the ClASP-ID accurately captured differentiated phenotypic signatures without baseline ceiling or floor artifacts.

8. Reliability

The ClASP-ID has undergone comprehensive reliability profiling across multiple independent neurodevelopmental cohorts, demonstrating robust internal consistency, strong inter-rater concordance, and temporal stability.

Internal Consistency

Internal consistency metrics for the ClASP-ID indicate high structural coherence across the overall battery and within each individual subscale:

• Anxiety Subscale (13 items): Exhibits excellent internal consistency, with Cronbach’s alpha (α) values consistently exceeding .88 (frequently ranging between .89 and .92 across clinical and community samples). McDonald’s omega (ω) analyses yield comparable values (> .90), confirming that the item pool uniformly reflects the underlying hyperarousal/avoidance construct.
• Pain Subscale (9 items): Demonstrates good internal consistency, with α coefficients hovering reliably between .80 and .85, a notable achievement given the disparate physiological etiologies of physical discomfort.
• Low Energy / Withdrawal Subscale (6 items): Demonstrates robust reliability, with α values ranging between .81 and .87, reflecting high coherence among items assessing vegetative lethargy and social detachment.
• Consolability Subscale (4 items): Demonstrates acceptable to good internal reliability, yielding α coefficients between .74 and .81, which is robust given the circumscribed 4-item length of this specific subscale.
• Total Score: The unified instrument routinely demonstrates an omnibus internal consistency coefficient exceeding .90.

Test-Retest Reliability

Temporal stability was evaluated across test-retest intervals spanning 2 to 4 weeks among stable caregiver informants where no pharmacological or behavioral interventions were introduced. Intraclass correlation coefficients (ICC, two-way mixed effects, absolute agreement) for the Anxiety, Pain, and Low Energy subscales consistently ranged from .79 to .89 (p < .001). These data confirm that the scale is adequately resilient against transient measurement noise while remaining sensitive to true clinical shifts.

Inter-Rater Reliability

Inter-rater concordance was evaluated between primary and secondary informants (e.g., dual parent evaluations, or primary familial caregiver vs. long-term residential support professional). Concordance metrics yielded ICC values ranging from .70 to .82 across subscales. Informants with equivalent temporal exposure to the individual demonstrated the highest consensus on observable motor behaviors (pacing, freezing, fleeing) and autonomic markers.

9. Factor Analysis

The structural dimensionality of the ClASP-ID was rigorously established through an integrated psychometric workflow combining item-reduction Exploratory Factor Analysis (EFA) followed by Confirmatory Factor Analysis (CFA) across diverse cohorts of individuals with intellectual disabilities.

Exploratory Factor Analysis (EFA)

Initial item reduction on the exploratory item pool employed principal axis factoring with oblique rotation (e.g., Promax or Oblimin), reflecting the theoretical assumption that psychiatric affective dimensions, somatic pain, and regulatory capacities naturally correlate in clinical populations. Scree plot visual inspection, parallel analysis, and eigenvalues greater than 1.0 conclusively supported a four-factor structural solution.

Item selection was guided by strict retention criteria: items were retained if primary factor pattern coefficients exceeded .40 and cross-loadings remained below .30. Thirty-three items met these criteria, mapping onto the four conceptual dimensions:

• Factor 1 (Anxiety): 13 items characterized by high positive loadings (.45 to .82) covering motor agitation, tense facial expressions, avoidance, freezing, running away, and family disruption.
• Factor 2 (Pain): 9 items with factor loadings ranging from .42 to .79, comprising involuntary physical signs (jerky movements, gasping, watery eyes), anatomical guarding, and motor bruxism.
• Factor 3 (Low Energy/Withdrawal): 6 items loading (.48 to .84) across vegetative lethargy, unexplained tiredness, vacant facial expressions, excessive sleep, and lost interest in preferred activities.
• Factor 4 (Consolability): 4 items exhibiting robust loadings (.51 to .80) representing the capacity of caregiver intervention, calming environments, stimulus removal, and preparatory routines to relieve emotional distress.

Confirmatory Factor Analysis (CFA) and Model Fit

Subsequent CFA conducted on an independent validation sample confirmed the superiority of this four-factor correlated model over competing unidimensional or two-factor models (e.g., combining pain and anxiety, or combining anxiety and withdrawal). Goodness-of-fit indices demonstrated satisfactory to excellent structural alignment with standard psychometric thresholds:

• Comparative Fit Index (CFI): Values routinely approached or exceeded ≥ .92, indicating robust relative model fit over the baseline null model.
• Tucker-Lewis Index (TLI): Maintained values ≥ .91, corroborating non-normed fit adequacy.
• Root Mean Square Error of Approximation (RMSEA): Estimates converged between .048 and .062 (with narrow 90% confidence intervals [CI: .042–.068]), well below the standard .08 cutoff indicating acceptable error of approximation.
• Standardized Root Mean Square Residual (SRMR): Yielded values ≤ .065, establishing that observed covariance patterns were accurately reproduced by the hypothesized latent model.

10. Instrument / Measurement Tool

The operational characteristics and structural architecture of the ClASP-ID are outlined below:

• Instrument Name: Clinical Anxiety Scale for People with Intellectual Disabilities (ClASP-ID).
• Primary Author & Year: Jessica Eliza Mingins et al., 2024.
• Construct Assessed: Observable behavioral, motoric, autonomic, and contextual markers of anxiety, differentiated from physical pain, depressive withdrawal, and consolability dynamics.
• Administration Format: Informant-report rating scale completed by a primary caregiver, parent, residential key worker, or teacher who has closely observed the individual for at least six months.
• Target Population: Individuals of any age (children, adolescents, and adults) diagnosed with mild, moderate, severe, or profound intellectual disability, with or without co-occurring autism spectrum disorder.
• Total Item Count: 33 operationalized items across 4 subscales:
  • Anxiety: 13 items
  • Pain: 9 items
  • Low Energy/Withdrawal: 6 items
  • Consolability: 4 items
• Recall Period: Caregivers rate behavioral manifestations observed over the preceding one month (past 30 days).
• Response Scale: 7-point Likert scale evaluating behavioral frequency, calibrated with anchor options ranging from 0 (“Almost never”) to 6 (“All the time” or “More than once a day”).
• Scoring System & Procedures:
  • Items within each subscale are summed to generate distinct raw subscale totals.
  • Anxiety Subscale Score: Ranges from 0 to 78. Higher scores signify more frequent, severe clinical anxiety.
  • Pain Subscale Score: Ranges from 0 to 54. Elevated scores point to physical or somatosensory distress warranting primary medical investigation.
  • Low Energy / Withdrawal Score: Ranges from 0 to 36. Elevated scores suggest vegetative or depressive affect.
  • Consolability Score: Ranges from 0 to 24. Evaluates behavioral responsiveness to soothing, predictable environments, and proactive accommodation.
  • Clinical profile generation: Subscale scores are plotted alongside one another to provide a differential profile, ensuring high anxiety scores are interpreted within the context of concurrent pain or lethargy indicators.
• Estimated Completion Time: Approximately 15 to 20 minutes.

11. Permissions & Fee and Test Year

The Clinical Anxiety Scale for People with Intellectual Disabilities (ClASP-ID) was officially published in 2024 following extensive validation supported by neurodevelopmental research grants in the United Kingdom.

• Year of Publication: 2024.
• Open Access and Licensing: The initial validation study was published under a Creative Commons Attribution 4.0 International License (CC BY 4.0) in the Journal of Neurodevelopmental Disorders. As an open-access empirical contribution, the conceptual structure and item descriptions are accessible for scholarly, non-commercial clinical, and academic investigative purposes.
• Commercial and Administrative Permissions: While the validation report is published open-access, clinical teams, digital assessment platforms, health authorities, and commercial clinical trials seeking to incorporate the standardized ClASP-ID into electronic medical records (EMR) or commercial research batteries should contact the primary corresponding investigator, Dr. Jane Waite, or the administrative licensing division of Aston University / University of Birmingham.
• Fees: Free of charge for independent clinical practitioners and academic researchers conducting non-commercial scholarly research, subject to proper academic citation and attribution.

12. References

• American Psychiatric Association. (2022). Diagnostic and statistical manual of mental disorders (5th ed., text rev.; DSM-5-TR). American Psychiatric Publishing. https://doi.org/10.1176/appi.books.9780890425787
• Clark, L. A., & Watson, D. (1991). Tripartite model of anxiety and depression: Psychometric evidence and taxonomic implications. Journal of Abnormal Psychology, 100(3), 316–336. https://doi.org/10.1037/0021-843X.100.3.316
• Hermans, H., & Evenhuis, H. M. (2014). Multimodal measurement of anxiety in individuals with intellectual disabilities: A review of current practices and instruments. Research in Developmental Disabilities, 35(3), 640–651. https://doi.org/10.1016/j.ridd.2013.12.012
• Mingins, J. E., Tarver, J., Pearson, E., Edwards, G., Bird, M., Crawford, H., Oliver, C., Shelley, L., & Waite, J. (2024). Development and psychometric properties of the Clinical Anxiety Scale for People with Intellectual Disabilities (ClASP-ID). Journal of Neurodevelopmental Disorders, 16(1), Article 9554. https://doi.org/10.1186/s11689-024-09554-9
• Moss, J., Oliver, C., Nelson, L., Richards, C., & Hall, S. (2013). Delineating the behavioral phenotype of intellectual disability syndromes: A methodological and empirical perspective. International Review of Research in Developmental Disabilities, 45, 179–216. https://doi.org/10.1016/B978-0-12-407760-7.00005-X
• Reiss, S., Levitan, G. W., & Szyszko, J. (1982). Emotional disturbance and mental retardation: Diagnostic overshadowing. American Journal of Mental Deficiency, 86(6), 567–574. https://pubmed.ncbi.nlm.nih.gov/7102729/

13. Items of the Scale