Pain Measurement in Infants and Children With and at Risk for Intellectual Disabilities

ABSTRACT

Standards of patient care require that comprehensive pain assessments be conducted at routine intervals. Infants and children with and at risk for intellectual disabilities, who are at high risk for experiencing pain, receive significantly less representation in the literature to inform pain measurement practice. The objectives of this review include (1) review and discuss the current literature surrounding pain measurement in infants and children with and at risk for intellectual disabilities, (2) define pain assessment tools, scales, and measures that are being used in infants and children with and at risk for intellectual disabilities, (3) discuss the strengths and limitations of the pain assessment tools, scales, and measures, (4) make recommendations for future pain research focused on this population. A narrative review of the literature regarding pain measures in infants and children with and at risk for intellectual disabilities was conducted using PubMed. A search strategy was created in consultation with a librarian scientist. There were no date limiters applied to the search. Pain measures can be classified as self‐report, behavioral (e.g., cry, facial expressions), physiological (e.g., heart rate, biomarkers, oxygen saturation, respiratory rate), and neurophysiological (electroencephalogram, functional magnetic resonance imaging, near infrared spectroscopy). There is a considerable dearth in the literature surrounding pain measures and pain indicators in this population, along with small sample sizes and inconsistent findings reported across studies. Future research is needed to compare pain responses across different age groups and intellectual disability diagnoses to neurotypical peers.

1. Introduction

The International Association of Pain defines pain as an “unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage” [1]. This broad and inclusive definition highlights that pain is highly individualized and personal, with possible variation in response across individuals. This variation may be more pronounced and more difficult to interpret in vulnerable populations, including those who are non‐verbal and cannot self‐report.

To adequately quantify the type and amount of pain that a patient is experiencing, standards of routine care require that comprehensive pain assessments be conducted at regular intervals using valid and reliable pain assessment tools [2]. This is especially pertinent in pediatric populations, as prolonged exposure to pain and untreated pain are associated with immediate and long‐term consequences, including negative future experiences with painful procedures [3], altered neurodevelopment [4, 5, 6], increased internalizing behaviors in the future [7], and the development of chronic pain [8]. To date, numerous pain measures have been developed and validated for use in pediatric populations [9, 10, 11]. However, a subset of this population—infants and children with and at risk for intellectual disabilities—has not received an equal representation in the literature to guide pain measurements [12].

Intellectual disabilities are defined as neurodevelopmental disorders beginning at birth or developing throughout childhood (before the age of 18 years) and are characterized by intellectual adversity, reduced adaptive skills and functioning, and difficulties with conceptual, social, and practical tasks of living [13]. Infants and children at risk for intellectual disabilities include those with chromosomal abnormalities, asphyxia, birth trauma, acquired illnesses involving the central nervous system, and those born extremely preterm [14, 15]. This population is at high risk for ubiquitous pain exposure, including the need for invasive diagnostic tests and procedures, higher rates of falls and accidental injuries, limited ability to comprehensively understand the implications of an injury or adequately communicate it to their caregiver, and lower levels of physical activity [16, 17].

The unequal representation in the literature of a population at high risk for pain exposure, who have been historically excluded from health and pain research, leads to numerous challenges related to pain measurement for healthcare providers [18].

2. Objectives

The objectives of this paper include: (1) reviewing and discussing the current literature surrounding pain measurement in infants and children with and at risk for intellectual disabilities, including (a) self‐report, (b) behavioral, (c) physiological, and (d) neurophysiological, (2) defining pain assessment tools, scales, and measures that are being used in infants and children with and at risk for intellectual disabilities, (3) discussing the strengths and limitations of the pain assessment tools, scales, and measures, and (4) making recommendations for future pain research focused on this population.

3. Methods

A narrative review of current literature regarding pain measures in infants and children with and at risk for intellectual disabilities was conducted in February 2025 using PubMed. As the literature pertaining to this subject area is limited, no date limiters were placed on the search. See Table 1 for the search strategy that was developed in consultation with a librarian. See Table 2 for the inclusion and exclusion criteria.

TABLE 1.

Search strategy.

#	Query	Results
1	Pediatric*[Title/Abstract] OR pediatric*[Title/Abstract] OR child*[Title/Abstract] OR infant*[Title/Abstract] OR adolescent*[Title/Abstract] OR “Young person”[Title/Abstract] OR youth*[Title/Abstract] OR teen*[Title/Abstract] OR preteen*[Title/Abstract] OR baby[Title/Abstract] OR babies[Title/Abstract] OR toddler*[Title/Abstract] OR boy*[Title/Abstract] OR girl*[Title/Abstract] OR “young people”[Title/Abstract] OR “young adult*”[Title/Abstract]	2 849 477
2	(MH “Child+”) OR (MH “Adolescence+”)	17 722
3	S1 OR S2	2 849 477
4	TI ((pain N2 (manag* OR mitigat* OR relief OR relieve* OR reduc* OR control OR treat* OR intervention or assess* or measure* or prevent*)) OR analges*) OR AB ((pain N2 (manag* OR mitigat* OR relief OR relieve* OR reduc* OR control OR treat* OR intervention or assess* or measure* or prevent*)) OR analges*)	241 849
5	(MH “Pain Management”) OR (MH “Patient‐Controlled Analgesia”) OR (MH “Analgesia”)	599
6	S4 OR S5	241 809
7	TI ((intellectual* OR learning OR cognit* OR development* OR neurologic*) N0 (disabil* OR disabl* OR impair* or disorder*)) OR AB ((intellectual* OR learning OR cognit* OR development* OR neurologic*) N0 (disabil* OR disabl* OR impair* or disorder*))	180 905
8	TI “down syndrome” OR “prader willi syndrome” OR “cerebral palsy” OR “fragile × syndrome” OR “autism” OR AB “down syndrome” OR “prader willi syndrome” OR “cerebral palsy” OR “fragile × syndrome” OR “autism”	125 154
9	(MH “Intellectual Disability+”)	1073
10	S7 OR S8 OR S9	288 307
11	S3 AND S6 AND S10	605

TABLE 2.

Inclusion and exclusion criteria.

Include	Exclude
Population
18 years and younger Any type of intellectual disability diagnosis Any infant diagnosed as “at risk” for intellectual disability	Older than 18 years Neurotypical population only Cerebral palsy diagnosis with no intellectual impairment Non‐human (mice)
Intervention/exposure
Studies reporting on pain measures (self‐report, behavioral, physiological, biobehavioural, neurophysiological) Studies evaluating pain measures (psychometric properties)	Studies evaluating pain management strategies
Comparator/context
Comparison to neurotypical populations, or no comparison	Only neurotypical population
Outcome
Pain scores Pain indicators Reliability, validity, and clinical utility	Responses to pain management interventions
Study characteristics
Quantitative Qualitative Observational Randomized controlled trials Reviews	Conference abstracts Case studies/reports Protocols

Following a systematic literature search of PubMed, studies were uploaded into Covidence (a web‐based platform that streamlines the production of systematic and other literature reviews). Titles and abstracts, followed by full texts, were screened by two independent reviewers against the inclusion criteria. A third reviewer was consulted if a disagreement occurred between the two independent reviewers.

4. Results

After reviewing the included studies, it was clear that pain measures can be categorized into one of the following: (1) self‐report, (2) physiological, (3) behavioral, (4) neurophysiological. Thus, the results are organized to reflect these categories.

4.1. Self‐Report Measures

Self‐report should always be trialed as a first step in pain measurement among children with intellectual disabilities, as it is considered of paramount importance [19, 20, 21]. It is critical that healthcare providers use a developmentally appropriate scale while assessing a child's pain, as using a scale that is too developmentally advanced for a child can result in the child's pain being under‐ or over‐treated [20, 22, 23]. When self‐report is not available, due to cognitive or linguistic limitations, a proxy report from parents is often recommended [24]. Overall, parents of children with intellectual disabilities have been shown to provide reasonable estimates of their pain [25].

Limited research has been undertaken to investigate the ability of children with intellectual disabilities to reliably self‐report their pain. Fanurik et al. [26] were the first to investigate the validity and reliability of self‐report in children (8–17 years) with varying degrees of intellectual disabilities (n = 47) in comparison to neurotypical children (n = 111). This was accomplished through the administration of tasks to evaluate their understanding of magnitude (i.e., ordering blocks according to size), ordinal position (i.e., ordering numbers), and using a numerical scale to rate pain levels in faces. Their study concluded that up to 50% of children with borderline cognitive impairment and 35% of children with mild cognitive impairment were able to correctly use the numerical pain‐rating scale. Limitations of this study include a relatively small sample size to represent the group of children with intellectual disabilities (n = 47), and reliance on the parents to state if their child had the intellectual capacity to partake in the study, as no formal cognitive assessments were completed due to time constraints. Benini et al. [27] investigated the self‐report ability of 16 children (7–18 years) with mild or moderate developmental delay during venipuncture using three conventional methods of self‐report (1. Visual Analogue Scale, 2. Eland Color Scale, 3. Faces Scale) in comparison to three modified self‐report measures (1. Cube Test, 2. Modified Eland Color Scale, 3. Modified Faces Scale). All children in this study were able to use the modified versions of the self‐report scales, with pain responses being consistent between the child, their parent, and the healthcare provider. The authors also found no difference in children's ability to use scales based on level of impairment (mild versus moderate) or etiology of intellectual disability (cerebral palsy versus Down syndrome). Limitations of this study include having a small sample size (n = 16) and that the modified self‐report measures have not been validated.

Due to the dearth in literature dedicated to validating self‐report measures of pain in children with intellectual disabilities, they cannot be recommended as a comprehensive measure of pain. However, the preliminary work by Benini et al. [27] and Fanurik et al. [26] provides a clear direction and need for future research focused on psychometrically evaluating both conventional and modified self‐report measures in children with intellectual disabilities and evaluating self‐report among different subgroups of intellectual disability.

4.2. Behavioral Measures

Behavioral measures, including facial expressions, body movements, and vocalizations, are often labeled as the most sensitive and reliable indicators of pain in nonverbal populations [15]. Of all the pain measures, behavioral measures have received the most attention in the literature among children with intellectual disabilities. See Table 3 for a list of behavioral pain assessment tools and measures that are used in infants and children with intellectual disabilities.

TABLE 3.

Behavioral pain measures in children with intellectual disabilities.

Name	Age	Information and indicators	Pain type
Non‐Communicating Children's Pain Checklist (NCCPC) [28] [42 items, six subscales] Non‐Communicating Children's Pain Checklist Revised (NCCPC‐R) [29] [30 items, 7 subscales] Non‐Communicating Children's Pain Checklist Postoperative Version (NCCPC‐PV) [30] [27 items, six subscales]	3–18 years	Designed specifically for nonverbal children with cognitive impairment 1. Vocal (moaning, whining, whimpering, crying, screaming, specific sound/word), 2. Eating/Sleeping (eating less, increased sleep, decreased sleep) a 3. Social (uncooperative, cranky, irritable, unhappy, withdrawn, seeking comfort/physical closeness, difficult to distract) 4. Facial (brow furrow, eye squeeze/wide eyes, turning down of mouth, lips puckered/quivering, teeth clenching/grinding/chewing tongue) 5. Activity (less active, agitated, fidgety) 6. Body/Limbs (floppy, spastic, gesturing to part of body, guarding, flinching, specific movements) 7. Physiological (shivering, change in color, sweating, tears, sharp intake of breath, holding breath)	Acute, chronic, post‐op
Pediatric Pain Profile (PPP) [31, 32]	1–18 years	Designed specifically for children with severe physical and learning impairments 1. Cheerful, sociable, responsive 2. Withdrawn, depressed 3. Hard to console 4. Crying, moaning, groaning, screaming, whimpering 5. Touching or rubbing certain body part 6. Restless, agitated 7. Flinching 8. Involuntary movements 9. Self‐injury 10. Flexed inwards, knees to chest 11. Tense, stiff 12. Twisted, tossed head, arched back 13. Resisted movement 14. Reluctant to eat 15. Disturbed sleep 16. Grimaced 17. Frowned, furrowed brow 18. Frightened 19. Grinding teeth 20. Hot and sweaty	Acute, chronic, post‐op
Faces, Legs, Activity, Cry, Consolability (FLACC) [19 items, five subscales] Revised Faces, Legs, Activity, Cry, Consolability (r‐FLACC) [33, 34] [42 items, five subscales]	2 months–7 years (FLACC) 4–19 years (r‐FLACC)	Original version designed for neurotypical children. Revised version designed for children with intellectual disabilities. 1. Face (no expression/smile, grimace/frown, withdrawn, quivering chin, clenched jaw, disinterested, sad b , appears worried b , distressed look b , fright/panic b ) 2. Legs (relaxed, usual tone and motion to limbs b , uneasy/restless, occasional tremors b , kicking/legs drawn upward, increased spasticity b , tremors b , jerking b ) 3. Activity (lying quietly, normal position, moves easily, regular respirations b , squirming, shifting back/forth, tense/guarded b , mildly agitated b , shallow/splinting respirations b , intermittent sighs b , arched/rigid, severe agitation b , head banging b , shivering b , breath holding b , gasping b , severe splinting b ) 4. Cry (no cry, moaning/whimpering, occasional complaint, occasional verbal outbursts b , steady crying, screams or sobs, constant grunting b , repeated outbursts b ) 5. Consolability (content/relaxed, reassured by touching/hugging, difficult to console and comfort, resisting care b )	Post‐op
COMFORT‐Behavior [35]	0–3 years	Not specifically designed for children with intellectual disabilities. Validated in infants with Down syndrome. 1. Alertness 2. Calmness 3. Physical movement 4. Facial tension 5. Muscle tone 6. Respiratory response/crying	Post‐op
Premature Infant Pain Profile Revised (PIPP‐R) [36, 37]	25–40 weeks	Designed for neurotypical infants. Appropriate for use among infants at risk for neurologic impairment. 1. Oxygen saturation 2. Brow bulge 3. Eye squeeze 4. Nasolabial furrow 5. Baseline behavioral state	Acute
Individualized Numeric Rating System (INRS) [38, 39]	3–17 years	Designed for nonverbal individuals and those with cognitive impairment. Indicators of pain are based on individual parent and healthcare provider assessment, rated from 0 (no pain, baseline) to 10 (severe pain). Parents are provided with a blank INRS with a list of various prompts to help them characterize their child's specific pain behavior, based on their history of painful events.	Post‐op

^a Not included in the NCCPC‐PV.

^b Specific to the r‐FLACC.

Dubois et al. [40] examined the relationship between 44 behavioral expressions of pain extracted from three validated scales (1. Non‐Communicating Children's Pain Checklist—Postoperative Version, 2. Face, Legs, Activity, Cry, Consolability—Revised, 3. Douleur Enfant San Salvadour) and demographic characteristics (i.e., chronological age, developmental age, socio‐adaptive skills) in children with intellectual disabilities (n = 30) and neurotypical children (n = 30) during the preoperative and postoperative period. They found significant differences in behavioral pain expression among children with intellectual disabilities who were verbal (mild to moderate intellectual disability) versus non‐verbal (severe to profound intellectual disability), where verbal children exhibited behaviors like those exhibited by neurotypical children of the same developmental age. Nonverbal children with intellectual disabilities lacked facial expressions (i.e., absence of pain‐specific facial expressions), body movements, vocalizations, and exhibited more atypical pain behaviors, significantly different from neurotypical children matched by both developmental and chronological age. Nader et al. [41] examined pain responses (1. Child Facial Coding System, 2. Observational Scale of Behavioral Distress, 3. Faces Pain Scale) during intravenous injection in 21 children with autism in comparison to 22 neurotypical children. In contrast to findings from Dubois et al. [40] they found that children with autism displayed significantly greater facial activity during the injection than neurotypical children. Likewise, Rattaz et al. [42] found that children with autism (n = 35) exhibited prolonged facial activity (Child Facial Coding System) in response to venipuncture in comparison to neurotypical children (n = 36).

Among infants with intellectual disabilities (n = 8), Mercer and Glenn [43] found they showed significantly less discrete pain expressions during vaccination than neurotypical infants (n = 30), as coded with the Maximally Discriminative Facial Movement Coding System (MAX). However, results must be interpreted with caution due to the small sample size. Similarly, Stevens et al. [15] found infants at moderate and high risk for neurological impairment exhibited significantly fewer total facial expressions following a heel lance than infants at low risk for neurological impairment, as coded with the Neonatal Facial Coding System. In an early study, infants with Down syndrome required more stimulation than neurotypical infants to produce a crying reaction and had an overall diminished visible response to pain [44]. A study by Aguilar Cordero et al. [45] yielded similar results, where infants with Down syndrome (n = 20) demonstrated diminished behavioral responses as measured with the VADONE (Assessment Pain Newborn) Scale in response to heel lance in comparison to neurotypical infants (n = 20). However, this study also found that when pain was perceived among the infants with Down syndrome, their pain responses persisted for a longer period than neurotypical infants, suggesting that reaction times are slowed among infants with Down syndrome. In contrast, Oberlander et al. [46] found no significant differences in heart rate variability or facial expressions during heel lance between infants with parenchymal brain injury (n = 12) and healthy infants (n = 12). Comparably, Valkenburg et al. [35] found that while infants with Down syndrome (n = 76) demonstrated higher pain scores during the preoperative and postoperative period than neurotypical infants (n = 466), the scores did not vary significantly between the two groups.

The evident variation in behavioral pain measures suggests that confounding factors may influence behavioral pain responses. While most studies examining behavioral pain responses in children with intellectual disabilities found that their facial expressions were more pronounced or prolonged than those of neurotypical children [41, 42], Dubois et al. [40] found that pain responses in children with intellectual disabilities were influenced by the child's level of socio‐adaptive abilities. Further, age may have a considerable influence on behavioral measures of pain in children with intellectual disabilities, as in contrast to the studies involving children with intellectual disabilities, studies examining behavioral measures in infants with intellectual disabilities found they exhibited fewer facial expressions during pain exposure [15, 43, 44, 45]. Thus, behavioral measures alone may only be appropriate for use beyond a certain chronological age.

4.3. Physiological Measures

Physiological measures are objective measures that are often used in clinical practice to monitor pain responses. Examples of these measures include heart rate, oxygen saturation, skin conductance, blood pressure, respiratory rate, and cortisol levels. A 2020 systematic review on the physiological measures of pain in different subject groups, including persons with severe or profound intellectual disabilities, concluded that research on physiological pain measures used in persons with intellectual disabilities is scarce, with a focus on infants and children with intellectual disabilities even more so [47].

Cardiac indices (i.e., minimum and maximum heart rate, heart rate variability) have been the most extensively studied in pediatric pain research, with inconsistent findings being reported [47, 48]. Rattaz et al. [42] measured heart rate and facial expression changes in children across three groups (1. Children with autism (n = 35), 2. Children with intellectual disability (n = 32), 3. Neurotypical children (n = 36)) during venipuncture. They found a mean increase in heart rate among all participants during the procedure, with no significant difference in heart rate between groups. Similarly, Stevens et al. [15] found a mean increase in heart rate and decrease in oxygen saturation during the most painful phases of a heel lance procedure among infant cohorts at low (n = 50), moderate (n = 45), or high risk (n = 54) for neurological impairment, with no significant differences between groups. In a small sample (n = 5) study by O'Leary et al. [49] investigating heart rate and skin conductance (electrodermal activity) changes in children with Rett syndrome during noxious (venipuncture) and non‐noxious (vital signs measurement) stimulation, they found significant increases in heart rate and skin conductance during venipuncture only. Interpretation of the study findings must be done with great consideration, due to the small sample size.

In contrast to the findings supporting changes in heart rate in response to a painful event, a small study by Oberlander et al. [50] found no significant increase in heart rate from baseline during both non‐noxious and noxious stimulation among adolescents with cerebral palsy and severe neurological impairment (n = 8). However, adolescents in this study did demonstrate a difference in their facial expressions during needle insertion, with significantly higher scores on the Visual Analogue Scale, speaking to an incongruence between heart rate and behavioral indicators of pain. This incongruence in physiological pain measures is further supported by preliminary findings from O'Leary et al. [49], as they found no significant correlation between physiological (heart rate and skin conductance) and behavioral (Faces, Legs, Activity, Cry, Consolability (FLACC) measurement) indicators during venipuncture among five children with Rett syndrome.

Biomarker collection and analysis may show promise in assessing pain in pediatric populations with intellectual disability. A variety of biomarkers, including neuropeptides, cytokines, and hormones (i.e., salivary cortisol), were analyzed among 10 nonverbal children with cerebral palsy during the preoperative period [51]. Using the Dalhousie Pain Interview, parents reported their child had no pain (n = 6) or mild to severe pain (n = 4). Biomarker levels in the pain group were found to be significantly higher compared to levels in the no pain group. Hunt et al. [32] analyzed the relationship between salivary cortisol and pain behaviors on the Pediatric Pain Profile among 29 children with cognitive impairment. They found that cortisol concentrations tended to be lower on average than those published for neurotypical children, and that there was a weak correlation between cortisol levels and behavioral indicators on the Pediatric Pain Profile; again, speaking to an incongruence between behavioral and physiologic indicators of pain. Spratt et al. [52] compared cortisol levels between 20 children with autism and 28 neurotypical children during a blood draw. They found a significant difference in serum cortisol obtained during the blood draw, with the children with autism displaying higher levels than neurotypical children. Furthermore, they found that while both groups displayed increased levels of salivary cortisol collected 20 min after the blood draw, the children with autism had sustained levels above their baseline 40 min after the blood draw, suggesting a prolonged response to pain, while neurotypical children dropped below their baseline level.

The current evidence suggests that there are considerable variations in pain responses captured by physiological measures [15, 32, 42, 49, 50, 52, 53]. While physiological measures are valuable objective measures that are not impeded by a child's age or level of intellectual functioning, they may be particularly susceptible to influence from confounding factors (e.g., opioid administration, previous pain exposure, stress, anxiety) that can change the pattern and interpretation of pain responses [20, 48, 54]. Further, it is important to note that these measures cannot measure pain directly; they measure physiologic activity that may be correlated with the subjective experience of pain but cannot be distinguished from changes due to stress or other forms of arousal. Therefore, the interpretation of these measures must be done with caution. Importantly, the use of physiological measures should be used in conjunction with other pain measures (e.g., self‐report, behavioral, neurophysiological) to obtain a comprehensive picture of the child's pain experience.

4.4. Neurophysiological Measures

Because most pain measures used in clinical practice are based on behavioral measures, which may not be pronounced in infants and persons with intellectual disabilities, this can lead to pain being mismanaged. Thus, neurophysiological measures, which encompass a new and emerging field for infants and children with intellectual disabilities, may provide a more comprehensive picture of pain processing in this vulnerable group. It is important to note that the following neurophysiological measures are not standard practice, but significant emerging areas worthy of discussion.

Electroencephalography (EEG) and event‐related potential (ERP) analysis have shown promise in discriminating pain from no pain in neurotypical children [55, 56, 57, 58]. Other studies have investigated sensory responses in children with intellectual disabilities more generally (i.e., not pain‐specific), and their findings can inform us as to how painful stimuli are processed. Chen and Fang [59] studied three sensory evoked potentials (1. Brainstem auditory evoked potentials, 2. Visual evoked potentials, 3. Short‐latency somatosensory evoked potentials) in 30 infants with Down syndrome and 25 neurotypical infants. They found that, overall, infants with Down syndrome demonstrated a variety of sensory deficits, including peripheral and central components of the nervous system. Findings from this study raise the question as to whether sensory impairments related to pain response exist in infants and children with Down syndrome, which has yet to be studied with EEG/ERP. Benromano et al. [60] likewise demonstrated that adults with intellectual disabilities (n = 16) display increased pain‐related ERPs when exposed to noxious stimuli in comparison to neurotypical controls (n = 25).

A study using functional magnetic resonance imaging (fMRI) to examine pain responses in adults with autism (n = 15) and neurotypical adults (n = 16) revealed that both neurotypical participants and those with autism had increased blood oxygenation level‐dependent (BOLD) during the early phase of pain stimulation [61]. However, during sustained pain stimulation, the participants with autism demonstrated significantly less BOLD signal, while neurotypical participants demonstrated increased BOLD signal. Another study investigated BOLD response using near infrared spectroscopy (NIRS) in children with intellectual disability and found increased activation in the primary motor cortex and somatosensory cortex during venipuncture in comparison to neurotypical children [62].

Structural imaging studies have revealed alterations in brain anatomy among children with varying forms of intellectual disability. Englander et al. [63] found a diffuse reduction of white matter in regions of the brain associated with the sensorimotor system in children with cerebral palsy and intellectual disability (n = 17). Similarly, neuronal loss in the cerebellum, brain stem, parietal and frontal cortices, and limbic system has been observed in children with autism [64]. While anatomical studies cannot in and of themselves reveal acute responses to painful stimuli, their findings reveal significant alterations in areas of the brain involved with sensory processing, which may be associated with alterations in the processing of pain [65].

Quantitative sensory testing (QST) is a primary method of identifying neuropathic pain syndromes in the clinical setting. Further, QST has been used to quantify pain sensitivity thresholds among children with intellectual disabilities. While traditional QST testing, which is reaction time dependent, may not be suitable for use among persons with intellectual disabilities due to their slowed sensory conduction, modified QST measurements may show promise. While QST measures are not currently sufficiently adapted for use in the clinical setting for children with intellectual disability or an inability to communicate their pain, QST in general is a main component of neurophysiological pain assessment.

Riquelme and Montoya [66] studied somatosensory processing, including pain sensitivity, among children (n = 15) and adults (n = 14) with cerebral palsy compared to neurotypical children (n = 15) and adults (n = 15). This study found that only children with cerebral palsy (i.e., not the adults with cerebral palsy) demonstrated an enhanced sensitivity for painful stimuli and reduced touch sensitivity in comparison to the matched neurotypical participants. Valkenburg et al. [67] compared pain sensitivity of 42 children with Down syndrome to their neurotypical siblings (n = 24) using QST. Specifically, they studied the children's abilities to discriminate between the perception of touch and sharpness, using both the method of limits (reaction time dependent) and the method of levels (reaction time independent). They found that children with Down syndrome had longer reaction times when exposed to heat and cold stimuli. Further, the children with Down syndrome were more sensitive to heat pain than their neurotypical siblings and displayed a trend towards being more sensitive to cold pain. Barney et al. [68] further modified traditional QST measurement in a case‐controlled study to suit the abilities of children with global developmental delay, by recording behavioral reactivity to the various sensory stimuli. This modification may make QST more feasible for use among persons who are non‐verbal or those with complex communication needs, as it removes the need for the child to respond verbally to the sensory stimuli (e.g., “I feel that,” “it hurts,” etc.). Using the Pain and Discomfort Scale (PADS), they recorded and subsequently coded behavioral reactivity (i.e., facial, vocal, gross motor) that occurred among 20 children with global developmental delay and 20 neurotypical children during modified QST testing. They found that children with global developmental delay were, on average, significantly more reactive than neurotypical controls to light touch, pin prick, cold, pressure, and repeated von Frey stimulation. In a study by Symons et al. [69], 16 children with global developmental delay completed a modified QST (mQST) protocol, a skin biopsy, and parent‐endorsed measures of pain. This novel study found that the children with global developmental delay displayed more behavioral reactivity in comparison to neurotypical children. Further, they found that children with more chronic pain had significantly greater epidermal nerve fiber density in comparison with children who did not have chronic pain.

The expensive and technically sophisticated nature of neurophysiological tools (i.e., timing, equipment, personnel training, burden, accuracy of data collection) acts as a significant barrier to using them to assess pain in a clinical setting in comparison to a controlled research setting [70, 71]. Worthy of discussion are the limitations associated with QST when reaction time is not considered, as persons with certain diagnoses (e.g., Down syndrome, Prader Willi syndrome) have been shown to have slowed reaction times to sensory stimuli. However, this limitation is primarily of concern in earlier studies using QST; the most recent QST studies have developed an approach that does not rely on reaction time, making this method more appropriate for persons with slowed reaction times. Moreover, it is important to mention that neurophysiologic measures analyze neurologic activity that may be correlated with the objective experience of pain. The highly objective nature of these measures, if validated by gold standard measures of pain (i.e., self‐report) in neurotypical children, could make them useful as a pain measurement tool for understanding how pain responses may be altered in children with intellectual disability at the neurophysiological level. Further, future investigations using neurophysiological measures could assist in characterizing the extent to which neurophysiological measures and other measures (i.e., self‐report, behavioral, bio‐behavioral) deviate from one another in children with intellectual disability.

5. Conclusion

This paper discussed pain measures that are used among infants and children with intellectual disability. Significant variations in pain indicators and the use of pain measures were evident across studies. These variations are likely attributed to the overall lack of literature available on pain measures and indicators in children with intellectual disabilities, small sample sizes used among studies that are conducted with this population, and a lack of comparative studies (e.g., comparing pain responses in children with intellectual disability to neurotypical children when exposed to the same painful stimulus). The use of neurophysiological pain measures in conjunction with other validated measures among children with intellectual disabilities has the potential to bridge a major gap in the literature surrounding how this population perceives and processes pain in comparison to neurotypical children. Importantly, findings from neurophysiological studies could also inform the effectiveness of pain treatment interventions in children with intellectual disabilities, which is another under‐studied area.

Though there is growing evidence in the literature to support that parental engagement in pain care yields positive outcomes for both the child and the parent [72, 73, 74, 75], there is a significant dearth highlighting the importance of the parent's role in pain care for children with intellectual disabilities.

While this paper discussed pain measures in the broad population of children with intellectual disability, significantly more research is needed to determine to what extent different subgroups of intellectual disabilities (e.g., Down syndrome in comparison to autism) and age groups (e.g., infants in comparison to children) may be associated with different pain responses, relative to neurotypical peers. This must be considered as a potential limitation of this review, as children with intellectual disabilities are discussed under one umbrella.

To date, there is ample research available to support that this population of infants and children perceives pain. Therefore, it is imperative that we consistently assess their pain and provide pain‐relieving strategies, just as we would to neurotypical infants and children, to achieve optimal and equitable care. Finally, in order to adequately advance pain care in this population, we must conduct primary research studies to ensure the consistent and appropriate application and use of evidence‐based pain measures, and refine the measures as needed.

Conflicts of Interest

The authors declare no conflicts of interest.

MacNeil M., Benoit B., Disher T., Newman A. J., and Campbell‐Yeo M., “Pain Measurement in Infants and Children With and at Risk for Intellectual Disabilities,” Paediatric and Neonatal Pain 7, no. 4 (2025): e70015, 10.1002/pne2.70015.

Data Availability Statement

Data sharing not applicable to this article as no datasets were generated or analyzed during the current study.