Somatic symptoms in pediatric patients with chronic pain: Proposed clinical reference points for the Children’s Somatic Symptoms Inventory (formerly Children’s Somatization Inventory)

Abstract

Among youth with chroic pain, elevated somatic symptoms across multiple body systems have been associated with greater emotional distress and functional disability and could represent poor adaptation to pain. The Children’s Somatic Symptoms Inventory (formerly the Children’s Somatization Inventory) is commonly used to assess somatic symptoms in children. However, no studies have evaluated the clinical utility of the measure in the assessment of pediatric patients with chronic pain. This study evaluated the factor structure and clinical relevance of the 24-item Children’s Somatic Symptoms Inventory (CSSI-24) in youth (n = 1150) with mixed chronic pain complaints presenting to a tertiary pain clinic. CSSI-24 total scores were equal or superior to factor scores as indicators of patients’ clinical characteristics (functional disability, pain catastrophizing, fear of pain, anxiety and depressive symptoms) and parental catastrophizing and protective responses. Tertile-derived clinical reference points for the CSSI-24 total score (<18: low, 19 – 31: moderate, ≥ 32: high) significantly differed on measures of clinical characteristics and parent factors. Controlling for age, sex, pain intensity and primary pain complaint, the high somatic symptoms group exhibited significantly greater health care utilization compared to the moderate and low groups. Assessment of somatic symptoms in pediatric patients with chronic pain may provide useful information regarding patients’ psychosocial risk and tendency to access health services.

Perspective:

Clinical reference points based on the CSSI-24 total scores meaningfully differentiated youth with chronic pain on measures of emotional distress, functioning, parent catastrophizing and protective responses, and health care utilization. Assessing somatic symptoms could provide useful information regarding a pediatric patient’s psychosocial risk, tendency to access health services, and need for enhanced care coordination.

Introduction

Somatic symptoms across multiple body systems frequently co-occur with chronic pain in both pediatric and adult populations^{1, 9} In youth with chronic pain, elevated somatic symptoms have been associated with greater pain severity and pain-related functional disability, negative pain cognitions, emotional distress, and the persistence of chronic pain into adulthood.^{6, 19, 23, 26, 35} Thus, it is possible that elevated somatic symptoms in pediatric patients with chronic pain could be useful information for their health care provider, serving as a red flag for poor adaptation to pain and poor prognosis.

Empirical research on pain includes many studies assessing somatic symptoms in pediatric patients with chronic pain^{3, 6, 19, 23, 26, 35} and in non-clinical populations.^{8, 11, 13, 17, 18, 20, 21, 27, 29} The most commonly used assessment tool is the Children’s Somatic Symptoms Inventory (CSSI) [formerly known as the Children’s Somatization Inventory (CSI)], a 35-item self-report and parent-report questionnaire developed in 1991,³² and reduced to 24 items in 2009 based on extensive psychometric evaluation.³⁰ The CSSI is a dimensional measure of the severity of bothersome nonspecific somatic symptoms experienced by children and adolescents.³¹

A number of research groups have conducted factor analyses to determine whether the measure is best characterized as a single, underlying dimension representing the overall severity of nonspecific somatic symptoms versus multiple dimensions representing the severity of unique clusters of somatic symptoms. Results of these analyses have been highly variable, identifying from 1 to 4 factors.^{8, 11, 13, 17, 18, 20, 21, 29, 30} Factors identified have included pseudoneurological symptoms, pain/weakness, cardiovascular symptoms, and gastrointestinal symptoms.^{8, 11, 13, 17, 18, 20, 21, 29} None of these studies has evaluated the clinical utility of factor scores in the assessment of a pediatric pain population and it is unclear whether the factors contribute more information than total scores alone in the assessment of pediatric patients with chronic pain. For example, it is not known whether factors representing clusters of somatic symptoms would differentially predict functional disability, emotional comorbidity, or mechanisms underlying pain persistence and disability.

Our first aim was to identify the factor structure of the CSSI-24 in a large sample of pediatric patients with mixed chronic pain diagnoses. Following the identification of CSSI-24 factors, we planned to evaluate the extent to which factor scores, compared to total scores, were associated with patients’ pain intensity, functional disability, pain-related fear and catastrophizing, emotional distress, and health service utilization, as well as parental catastrophizing and protective responses to their children’s pain. If CSSI-24 factors contributed additional information beyond CSSI-24 total scores, then it would be important to consider both factor scores and total scores. Our second aim was to identify clinical reference points representing low, medium, and high levels of somatic symptoms on the CSSI-24. Such reference points may be useful for clinicians in understanding the extent of patients’ somatic distress.

Methods

Participants

The present study comprised 1150 children between the ages of 8 – 17 years (mean age = 13.8, SD = 2.4), who presented for evaluation at an outpatient multidisciplinary pain clinic in the north‐eastern region of the United States between September 2008 and April 2014. Of published studies derived from this large clinical database, two have reported data related to the CSSI-24.^{14, 25} Participants were primarily Caucasian (96.2%) and female (79.1%), which is consistent with the population of pediatric patients seen in this tertiary-care setting. Patients presented with a diverse set of pain complaints including localized musculoskeletal pain, diffuse musculoskeletal pain, neuropathic pain, abdominal pain, headache, and other (see Table 1). The majority of parents had completed a college or higher education degree (48.5% mothers, 42.7% fathers).

Table 1.

Sample demographics and characteristics

Variable	Frequency n (%)
Child Demographics
Gender
Male	240 (20.9)
Female	910 (79.1)
Race
White	1039 (90.3)
Black or African American	29 (2.5)
Asian	19 (1.7)
American Indian or Alaskan	1 (0.1)
Native
Multiracial	37 (3.2)
Not reported	25 (2.2)
Ethnicity
Non-Hispanic or Latino	1078 (93.7)
Hispanic or Latino	43 (3.7)
Not reported	29 (2.6)
Child Pain Characteristics
Neuropathic	294 (25.6)
Localized Musculoskeletal	511 (44.4)
Diffuse Musculoskeletal	80 (7.0)
Headache	54 (4.7)
Abdominal	170 (14.8)
Other	41 (3.5)

Procedures

Children and accompanying parent or caregiver who presented at a large tertiary pain clinic in the Northeast region of the United States completed a standard battery of measures as part of their multidisciplinary clinical evaluation. Questionnaires were mailed or sent electronically through email and completed prior to their appointment. This study was approved by the Institutional Review Board as a retrospective record review examining pain-related psychological factors in pediatric chronic pain.

Measures

Demographics and Medical Variables

Relevant demographic (i.e. age, sex, pain duration) and medical variables (i.e. diagnosis, pain rating) were extracted via medical chart review.

Somatic Symptoms.

The Children’s Somatic Symptoms Inventory-24 (CSSI-24) (formerly known as the Children’s Somatization Inventory-24) is a child self-report measure^{30, 31} adapted from an earlier 35-item version.^{32, 33} This questionnaire assesses somatic distress – the extent to which youth are bothered by various non-specific somatic symptoms. Youth report how much they were bothered by each symptom during the past two weeks on a 5-point scale from “0 = not at all” to “4 = a whole lot”. Examples of symptoms on the CSSI include heart beating too fast, difficulty breathing, headache, chest pain, nausea, and joint and limb pain. Total scores are calculated by computing the sum of item responses yielding total scores ranging from 0–96.

Functional Disability.

The Functional Disability Inventory (FDI)³⁴ is a 15-item child self-report measure assessing perceived difficulty in performing common activities in the domains of school, home, recreation, and social interactions. Participants rate the difficulty they had in carrying out each activity in the preceding 2 weeks (0 “no trouble”; 4 “impossible”). The FDI consists of 15 items and yields a total score that can range from 0–60, with higher scores indicating greater disability. Clinical reference points have been established such that total scores of 0–12 reflect low disability, 13–29 reflect moderate disability, and scores greater than or equal to 30 reflect severe disability.¹⁵

Pain Catastrophizing.

The Pain Catastrophizing Scale (PCS-C)⁴ is a 13-item child self-report measure assessing rumination, magnification, and helplessness within the context of pain. Participants rate 13 items on a 0–4 scale to create a total score from 0–52. Higher scores indicate more pain catastrophizing. A total score of 26 or greater reflects the clinical reference point for high catastrophizing.²² Parents also completed a parent-report version of this measure: the PCSC-P,¹² in which parents report on their own rumination, magnification, and helplessness regarding their child’s pain.

Pain-Related Fear.

The Fear of Pain Questionnaire (FOPQ-C)²⁵ is a 24-item child self-report measure assessing pain related-fear and avoidance of activities. Higher total scores indicate greater fear and avoidance and, based on established clinical reference points, a total score of 51 or greater is considered high pain-related fear.²⁵

Depressive Symptoms.

The Children’s Depression Inventory (CDI-2)¹⁶ is a 28-item child self-report measure assessing depressive symptoms. Scores on the CDI were converted to T-scores with a mean of 50 and standard deviation of 10. Higher T-scores indicated greater levels of depressive symptoms. T-scores of 65 or greater are classified as clinically significant.¹⁶

General Anxiety.

The Revised Children’s Manifest Anxiety Scale (RCMAS)²⁴ is a 45-item child self-report measure assessing anxiety symptoms. Items, excluding the lie scale items, are summed to obtain a total anxiety score and then converted to T-scores. T-scores have a mean of 50 and a standard deviation of 10. T-scores of 60 or greater are classified as clinically significant.

Parent Protective Behaviors.

The Adult Response to Children’s Symptoms (ARCS)²⁸ is a 29-item self-report questionnaire completed by a parent or caregiver. The 13-item Protect subscale measures protective parental behaviors towards the child. The mean score on the Protect subscale was used in this study and ranged from 0 to 4.

Healthcare Utilization.

Items regarding the child’s healthcare use were completed by the parent or caregiver. Items prompt parents to report the number of doctor visits, number of times in the ER, and number of overnight stays in the hospital in the past 3 months because of the child’s pain.

Data Analysis

Data analyses were conducted with SPSS software, version 24.0 (SPSS, Chicago, IL). Maximum likelihood exploratory factor analysis (EFA) with oblique rotation was conducted initially to determine the factor structure of the CSSI-24 in a pediatric chronic pain sample. Factor analysis was repeated until a solution was generated in which all items loaded adequately on the empirically-derived factors. The final factor solution was determined by examining eigenvalues (>1 indicates good fit) and scree plot. Pearson r zero-order and partial correlations evaluated the association of CSSI-24 factor scores and CSSI-24 total scores to measures of physical and psychological functioning. Next, clinical reference points were derived for the CSSI-24 based on tertiles. Clinical reference groups were first compared on key demographic factors (age, sex, primary pain complaint, and typical pain intensity). ANCOVA analyses, controlling for age, sex, primary pain complaint, and pain intensity, evaluated the relation between the CSSI-24 clinical reference groups and measures of children’s functional disability, fear of pain, pain catastrophizing, anxiety, depression, parent protective responses, and parent catastrophizing about children’s pain. Logistic regression analyses, with age, sex, primary pain complaint, and typical pain intensity as covariates, evaluated the relation between CSSI-24 clinical reference groups and binary health service utilization variables (ED visit in past 3 months, hospitalization in past 3 months, consulted > 5 physicians for pain).

Because these data were collected in the context of questionnaires for clinical use, a small subset of patients occasionally skipped a questionnaire or did not complete a measure. However, data were available for over 94% of the sample for the majority of measures (pain intensity, disability, depression, anxiety, parent protective responses). A few measures had data available for only 70% of the sample (Fear of Pain Questionnaire and Pain Catastrophizing Scale-Child and Parent Report) due to a gap in administration of these measures between August 2010 and March 2012. Participants who completed versus did not complete these measures did not differ significantly on age, sex, or CSSI-24 total scores. Thus, missing data were considered to be missing at random and were handled with pairwise deletion.

Results

Exploratory Factor Analysis

The 24 items of the CSSI-24 were entered into a maximum likelihood factor analysis with oblique rotation. The criterion of eigenvalue > 1 resulted in an initial five factor solution. However, examination of the scree plot indicated a three-factor solution best characterized the data and provided potentially clinically meaningful symptom clusters. All but two items met the recommended 0.32 factor loading threshold on a given domain,⁵ but these two items were retained on the initial factor as no cross-loadings > 0.25 on another factor were observed. In fact, no cross-loading > 0.25 was observed for any item on the scale. Table 2 presents the item loadings for the three-factor solution.

Table 2.

Factor structure of the CSSI-24 in youth with chronic pain

	Factor Loading
Item	Physiological Arousal	Myalgia	GI	Mean	SD
7. Trouble getting your breath (when not exercising)	.788			0.66	1.10
16. Heart beating too fast (when not exercising)	.759			0.58	1.07
3. Pain in the heart or chest	.725			0.81	1.21
17. Difficulty swallowing	.474			0.27	0.73
2. Faintness or dizziness	.466			1.17	1.26
19. Blurred vision (even with glasses on)	.427			0.49	0.93
8. Hot or cold spells	.408			1.20	1.42
18. Loss of voice	.323			0.22	0.65
1. Headaches	.287			1.78	1.37
10. Weakness in parts of body		.776		1.96	1.49
24. Pain in arms or legs		.758		2.13	1.62
23. Pain in knees, elbows, or other joints		.671		2.13	1.62
11. Heavy feelings in arms or legs		.653		1.08	1.35
6. Sore muscles		.628		2.06	1.42
9. Numbness or tingling		.485		1.52	1.48
4. Feel low in energy or slowed down		.375		2.18	1.39
5. Pain in lower back		.308		1.81	1.60
12. Nausea or upset stomach			.780	1.40	1.46
15. Pain in stomach or abdomen			.777	1.45	1.51
22. Food making you sick			.677	0.68	1.16
14. Loose bowel movements/diarrhea			.587	0.43	0.94
21. Bloating (gassy)			.586	0.76	1.17
13. Constipation			.551	0.73	1.22
20. Vomiting			.456	0.24	0.72

Factor 1, labeled Physiological Arousal, consisted of 9 somatic symptoms that may be heightened in response to sympathetic nervous system activation. Factor 2, labeled Myalgia, consisted of 8 somatic symptoms associated with widespread pain, fatigue, and weakness. Factor 3, labeled Gastrointestinal (GI), consisted of 7 somatic symptoms associated with the GI system. The Physiological Arousal factor exhibited large magnitude correlations with the Myalgia (r = 0.54, p < 0.01) and GI (r = 0.53, p < 0.01) factors. The GI and Myalgia factors were also significantly correlated (r = 0.24, p < 0.01), but the magnitude of the correlation was small. Alpha reliability for the Physiological Arousal, Myalgia, and GI factors were 0.82, 0.83, and 0.83, respectively.

Relation of CSSI-24 Factors and CSSI-24 Total Score to Clinical Characteristics

Table 3 presents zero-order correlations of CSSI-24 factor scores and the CSSI-24 total score to measures of children’s physical and emotional functioning as well as to parent responses to children’s pain. As expected, both CSSI-24 factor scores and the CSSI-24 total score exhibited small to medium zero-order correlations with children’s functional disability, fear of pain, pain catastrophizing, anxiety, and depressive symptoms. The CSSI-24 total score and scores on the Physiological Arousal and Myalgia factors, but not on the GI factor, exhibited small, but significant correlations with children’s typical pain intensity. All three factors and the total score also exhibited significant, but small, correlations with parent responses to children’s pain, i.e., protective responses and catastrophizing about their child’s pain.

Table 3.

Zero-order and partial correlations between CSSI-24 subscales and measures of children’s physical and emotional functioning and parent responses to children’s pain

	Sample Size	CSSI Total	CSSI Physiological Arousal		CSSI Myalgia		CSSI Gastrointestinal
Child-reported	n	Zero-order	Zero-order	Partial	Zero-order	Partial	Zero-order	Partial
Typical pain intensity	1086	0.15**	0.10	0.01	0.20**	0.17**	0.03	−0.02
Functional disability	1145	0.50**	0.38**	0.09	0.52**	0.41**	0.23**	0.07
Fear of pain	793	0.53**	0.46**	0.18**	0.42**	0.25**	0.38**	0.21**
Pain catastrophizing	794	0.34**	0.29**	0.10	0.31**	0.20**	0.20**	0.07
Depressive symptoms	1113	0.45**	0.39**	0.16**	0.37**	0.22**	0.29**	0.12**
Anxiety	1114	0.47**	0.41**	0.16**	0.37**	0.21**	0.33**	0.17**
Parent-reported
Protective responses	1096	0.26**	0.25**	0.12**	0.13**	0.01	0.26**	0.15**
Catastrophizing about child’s pain	782	0.20**	0.17**	0.07	0.19**	0.11	0.09	0.01
Child age	1150	0.13**	0.09	0.001	0.11**	0.08	0.10	0.06
Child sex	1150	0.04	0.03	0.01	0.07	0.06	−0.02	−0.03

Note. Partial correlations controlled for the other two CSSI subscales in order to assess unique relations between each subscale and other study measures.

^**p < 0.001

Because all three factors were significantly correlated, partial correlations further evaluated the utility of the separate factors by examining associations between each factor and study measures, controlling for the other two factors (Table 3). With few exceptions, the CSSI-24 total score was more strongly associated with the clinical characteristics than the CSSI-24 factor scores. Moreover, no clinically meaningful pattern emerged between factor scores and particular clinical characteristics. Thus, CSSI-24 factor scores did not contribute additional information beyond CSSI-24 total scores in understanding the association between somatic symptoms and clinical characteristics.

Clinical Reference Points for CSSI-24 Total Scores

To facilitate a clinician’s ability to quickly interpret the CSSI-24 scores of individual patients at the time of their clinical evaluation, we identified reference points that defined CSSI-24 total scores as low, moderate, or high. To validate the reference points, we evaluated whether patients scoring in the low, moderate, and high clinical reference groups differed significantly on other clinical characteristics (e.g., functional disability, depressive symptoms, and anxiety). Clinical reference points for CSSI-24 total scores were based on tertiles, similar to reference points generated for the Pain Catastrophizing Scale for Children²² and the Functional Disability Inventory.¹⁵ Specifically, CSSI-24 total scores between 0 and 18 were in the lowest tertile and represented low somatic symptoms, scores between 19 and 31 represented moderate somatic symptoms, and scores ≥ 32 represented high somatic symptoms.

CSSI-24 clinical reference groups significantly differed by age, F(2,1149) = 10.39, p < 0.001, η_p² = 0.02, primary pain complaint, Χ²(10) = 53.53, p < 0.001, and typical pain intensity, F(2,1083) = 14.31, p < 0.001, η_p² = 0.03, but not sex, Χ²(2) = 2.46, p = 0.29. Specifically, children in the high somatic symptom group were significantly older (mean age = 14.18, SD = 2.30) and reported higher pain intensity (mean = 6.37, SD = 1.94) than children in the moderate (mean age = 13.88, SD = 2.38, mean pain = 5.90, SD = 2.19) and low (mean age = 13.41, SD = 2.48, mean pain = 5.59, SD = 2.22) somatic symptom groups. A greater proportion of children with diffuse musculoskeletal pain (60%, n = 48) reported symptoms in the high somatic symptom group compared to other diagnostic groups (neuropathic: 32.3%, n = 95, local musculoskeletal: 28.4%, n = 145, abdominal: 37.1%, n = 63). A substantial proportion of children with headaches also reported symptoms in the high clinical range (55.6%, n = 30). Given that this institution has a separate headache clinic (Pediatric Headache Program) where the majority of headache patients are seen, those who present to the chronic pain clinic are typically more complex and likely do not represent children with headaches more broadly.

One-way ANCOVA analyses, controlling for child age, sex, primary pain complaint, and typical pain intensity, evaluated differences between CSSI-24 clinical reference groups on measures of children’s clinical characteristics (Table 4). Results indicated that CSSI-24 clinical reference groups significantly differed on functional disability, fear of pain, pain catastrophizing, depressive symptoms, and anxiety. The largest effect sizes were observed for differences on functional disability, fear of pain, and anxiety. Pairwise comparisons indicated that youth with low, moderate, and high somatic symptoms reported the lowest, moderate, and highest levels respectively of pain catastrophizing, fear of pain, anxiety, depressive symptoms, and functional disability.

Table 4.

One-way ANCOVAs evaluating differences between CSSI-24 clinical reference groups on common measures of pediatric pain, emotional symptoms, and functioning

Variable	Low Mean (SD)	Moderate Mean (SD)	High Mean (SD)	f	ηp2
Child-reported
Functional disability	15.82 (10.29)a	22.69 (10.82)b	29.05 (9.91)c	142.25	0.21
Fear of pain	32.94 (16.95)a	42.27 (17.56)b	57.37 (16.45)c	115.19	0.24
Pain catastrophizing	23.92 (10.55)a	27.90 (11.45)b	33.23 (11.42)c	33.10	0.08
Depressive symptoms	45.81 (9.59)a	50.92 (10.87)b	58.41 (12.48)c	97.24	0.16
Anxiety	42.03 (9.86)a	48.16 (10.30)b	55.35 (10.69)c	134.55	0.21
Parent-reported
Protective responses	1.27 (0.65)a	1.40 (0.59)b	1.63 (0.63)c	32.66	0.06
Catastrophizing about child’s pain	24.57 (9.75)a	25.35 (9.44)a	29.63 (10.26)b	15.52	0.04

Note. ANCOVAs controlled for child age, sex, primary pain complaint, and typical pain intensity. All f values statistically significant at p < 0.001 level. Means presented in table are raw means, but group comparisons were tested on estimated marginal means adjusted for covariates. Group comparisons indicate Bonferroni post hoc pairwise comparison significant at p < 0.05 level with different superscripts denoting differences among groups; a < b < c

Regarding parent responses to children’s pain, levels of parent protective responses mirrored the clinical reference point groups such that parents of youth with low, moderate, and high somatic symptoms reported the lowest, moderate, and highest levels, respectively, of protective responses. For catastrophizing about children’s pain, parents of youth in the high somatic symptoms group reported the highest levels; parents of youth in the low and moderate somatic symptoms groups did not differ significantly on catastrophizing about children’s pain.

Finally, health care utilization differed significantly for the CSSI-24 clinical reference groups. Binary logistic regressions controlling for child age, sex, typical pain intensity, and primary pain complaint indicated that patients in the high CSSI-24 clinical reference group, compared to the moderate CSSI-24 clinical reference group, had 1.51 (95% CI: 1.06, 2.14) times higher odds of visiting the emergency room, 1.92 (95% CI: 1.21, 3.06) times higher odds of overnight hospitalization, and 1.80 (95% CI: 1.25, 2.59) times higher odds of consulting more than 5 medical providers regarding pain (Figure 1). Compared to the low CSSI-24 clinical reference group, the high CSSI-24 clinical reference group had 1.94 (95% CI: 1.35, 2.79) times higher odds of visiting the emergency room in the past 3 months, 2.35 (95% CI: 1.44, 3.83) times higher odds of overnight hospitalization in the past 3 months, and 2.00 (95% CI: 1.37, 2.92) times higher odds of consulting more than 5 medical providers regarding pain. Patients in the low and moderate CSSI-24 clinical reference groups did not differ significantly with regard to healthcare utilization.

Figure 1.

Health care utilization by CSSI-24 clinical reference group

*Proportion of youth in high somatic symptoms group significantly differed from proportion of youth in moderate and low somatic symptoms groups at p < 0.05 level.

Discussion

This study makes two important contributions to the literature on somatic symptoms in pediatric patients with chronic pain. First, we conducted a factor analysis of the CSSI-24 in the largest clinical sample of pediatric pain patients to date and identified factors representing clusters of somatic symptoms associated with (1) physiological arousal (e.g., heart palpitations, shortness of breath), (2) myalgia (e.g., weakness, limb and joint pain), and (3) the gastrointestinal tract (e.g., nausea, abdominal pain). By comparing the relation of CSSI-24 factor scores versus CSSI-24 total scores to various clinical characteristics of the patients, we showed that CSSI-24 total scores were equal or superior to factor scores as indicators of patients’ clinical characteristics. Therefore, we recommend that clinical assessment of somatic symptoms in pediatric patients with chronic pain focus on CSSI-24 total scores.

The second important contribution of this study is the identification of reference points for interpretation of the CSSI-24 total score for somatic symptoms as an indicator of a potential relation to other clinical characteristics (e.g., functional disability, emotional distress). Patients in the low, moderate, and high clinical reference groups for CSSI-24 total scores differed significantly on measures of pain intensity as well as psychological well-being and daily functioning. The strongest differences among the clinical reference groups, controlling for patient age, sex, and primary pain complaint, were for functional disability, fear of pain, and anxiety. Higher scores on measures of these variables significantly differentiated patients in the high CSSI-24 group from those in the moderate and low CSSI-24 groups. Regarding parent-report measures, parents of youth in the high CSSI-24 reference group, compared to parents of youth in the moderate and low CSSI-24 reference groups, reported significantly greater protective responses and catastrophizing about their children’s pain. The relation between parent behavior and children’s somatic symptoms is likely bidirectional such that higher levels of children’s somatic symptoms elicit greater parental concern and greater parental concern may, in turn, increase the severity of children’s somatic symptoms by directing children’s attention to their somatic sensations and eliciting fear. Finally, based on parent report, youth in the high CSSI-24 reference group had significantly higher levels of recent health care utilization than youth in the moderate and low CSSI-24 reference groups. This finding is consistent with other studies showing that high levels of somatic symptoms drive health care seeking across multiple specialties (Campo, Jansen-McWilliams et al, 1999; Escobar, Cook et al, 2010).^{2, 7}

Study results suggest important directions for clinical practice and research on pediatric chronic pain. Specifically, identifying patients in a pediatric pain clinic who present with high levels of somatic symptoms could prompt more intensive care coordination across multiple pediatric subspecialties where the patient may present for evaluation and treatment of their symptoms. In primary care and other subspecialty settings the CSSI-24 could be useful in clinical assessment as a red flag for psychosocial risk factors including anxiety, depression, and pain catastrophizing that have been associated with poor pain prognosis. Those patients with high scores on the CSSI-24 (Total ≥ 32) could receive additional, more in-depth psychological evaluation or referral for intensive interdisciplinary treatment. Further, higher levels of somatic symptoms were associated with greater disability and poorer psychological adjustment even when taking into account pain intensity and primary pain complaint. This emerged as stair-step effect where youth with moderate somatic symptoms experienced greater disability and poorer psychological adjustment compared to those with low somatic symptoms, but lower disability and better psychological adjustment compared to the high somatic symptom group. Thus, targeting nonspecific somatic symptoms in treatments for youth with chronic pain, particularly when elevated in the moderate or high reference groups, could prove important for improving treatment efficacy and outcomes.

Because of the cross-sectional design of this study, the nature of temporal relations between somatic symptoms and other clinical characteristics cannot be inferred. For example, it is plausible that the experience of chronic pain precipitates or exacerbates anxiety and depression that manifest as somatic symptoms. Alternatively, chronic pain and emotional distress may both arise from a third unmeasured variable. Longitudinal studies are needed to evaluate mechanisms underlying the association between somatic symptoms and measures of psychosocial risk. Another useful direction for clinical research would be in randomized controlled trials of behavioral interventions for pediatric chronic pain. For example, the effectiveness of cognitive behavioral therapy in reducing chronic pain has been demonstrated¹⁰ but whether treatment effects extend to somatic symptoms is unknown. The homogeneity and nature of the present sample (recruited from a single, tertiary care pediatric chronic pain clinic) limit the generalizability of our findings. CSSI-24 scores and reference points should be further evaluated in a more diverse sample as well as in other settings (e.g., primary care, a school-based population, non-pain specific tertiary care settings). Further research is needed in these types of settings to determine whether the CSSI-24 could inform referral for psychological assessment and treatment.

In sum, the CSSI-24 represents a clinically useful measure of somatic symptoms in pediatric patients with chronic pain. CSSI-24 total scores provide a comprehensive picture of bothersome somatic symptoms in youth and correspond with other clinical measures of pain catastrophizing, fear of pain, anxiety, and functional disability. Routine assessment of somatic symptoms in pediatric chronic pain clinics may provide useful information regarding a patient’s psychosocial risk and the need to be alert for increased health service utilization requiring enhanced coordination of care among providers representing various subspecialties.

Highlights.

• CSSI total scores were superior to factor scores as indicators of clinical features

• Clinical reference groups were derived based on CSSI-24 total score tertiles

• The high somatic symptom group had greatest disability and psychological distress

• High somatic symptoms corresponded with significantly greater health service use