Somatic symptoms in psychiatry include underlying depression, anxiety, or other psychiatric disorders. This study aimed to conduct a validation study of a Korean version of the Somatic Symptom Scale-8 (K-SSS-8), and to utilize the K-SSS-8 effectively in clinical settings.
For reliabilty, test-retest reliability and internal consistency were analyzed. For construct validity, exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) were conducted. Known-group validity was verified, Jonckheere-Terpstra test (J-T statistic) were used.
Maternal Cronbach’s alpha was 0.85 and r value of test-retest reliability was 0.777. In the EFA, 2-, 3- and 4-factor model showed cumulative percentile for variance of 60% or more. In the CFA, the 3-factor model was found to be the most appropriated and simplest (χ2=10.992, df=17, CFI=1.000, TLI=1.022, RMSEA=0.000). The verifying the difference in K-SSS-8 also showed significant difference. (J-T statistic=-2.510, p<0.05).
K-SSS-8 can be useful for exploring symptoms such as panic symptoms, physical pain, and physiological symptoms experienced by patients in a short time. In addition, the K-SSS-8 is expected to be very useful for determining the current severity by using the severity categories and for establish additionally required assessment plans for depression and anxiety symptoms.
Somatic symptoms commonly include cardiopulmonary, gastrointestinal, pain, and general symptoms [
The PHQ is a tool that can easily screen depression, anxiety, alcohol, eating, and somatic symptom-related mental disorders when diagnosing patients. The PHQ has been translated into over 20 languages, and is widely used worldwide [
The SSS-8 is composed of a total of 8 items excluding items regarding menstrual problems, sexual problems, and fainting contained in the PHQ-15. It was originally developed by Kroenke et al. [
This study aimed to conduct a validation study of a Korean version of the SSS-8 (K-SSS-8), and to utilize the K-SSS-8 effectively in clinical settings.
Before developing the K-SSS-8, we first obtained permission from the original authors of the SSS-8 for the validation study of the Korean version. Subsequently, 3 psychiatrists and 1 clinical psychologist translated the SSS-8 into Korean, and an individual with a doctorate degree in the US, who are fluent in both English and Korean, back-translated the Korean version. After 2 psychiatrists and a psychologist with a PhD in psychology conferred, the K-SSS-8 was finalized (
The study period was from March 2017 to March 2019. The participants consisted of healthy controls and patients. The healthy controls included 188 public officers working in small- and medium-sized cities in Jeollabuk-do, South Korea. Data from a total of 167 public officers, except for 11 with insufficient responses and 10 with serious medical conditions, were used for analysis. Among them, a total of 31 were retested for test-retest reliability testing after 3–4 weeks. In the case of the patient group, the participants were 32 patients who visited the Department of Psychiatry at our hospital and complained of somatic symptoms. Among them, data from a total of 23 patients, except for those with a high degree of psychosis and underlying serious and obvious medical conditions, were used for analysis. This study was approved by the Institutional Review Board of Wonkwang University Hospital (No. WKUH 2017-04-007-001), and all the participants provided written informed consent before starting the study.
The EuroQol 5 Dimension (EQ-5D), the PHQ-15, and the PHQ-2 scales were used to test the reliability and validity of the K-SSS-8.
The EQ-5D was developed to measure general health status [
The PHQ-15 is a scale that consists of 15 items only related to somatic symptoms among all the items contained in the PHQ. Each item is rated on a 0-2-point scale, and the total score ranges from 0 to 30 points. In this study, the Korean version of the PHO-15 translated by Han et al. [
The PHQ-2 consists of two items regarding depression among the items contained in the PHQ-9. The two items ask about depression and anhedonia respectively. As in a study regarding the Japanese version of the SSS-8, a binary response consisting of “yes” or “no” was used in this study. If anyone responds with “yes” to at least one item, he or she is considered to have depression. Using this, the participants were divided into three groups according to the degree of depression (group 1: depression-positive for two items; group 2: depression-positive for one item; and group 3: depression-negative for two items), and the degree of somatic symptoms according to the group was analyzed.
First, frequency analysis was performed for descriptive statistics of the participants. Internal consistency and test-retest were used to validate reliability. Internal consistency was tested using Cronbach’s alpha. Pearson correlation analysis was performed to verify test-retest. Construct validity and concurrent validity verification were performed to test validity. Exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) were performed to verify construct validity, and correlation analysis was performed to verify concurrent validity. The Maximum Likelihood (ML) and Oblique rotation (Direct Oblimin) methods were used for the EFA, while Tucker-Lewis Index (TLI), Comparative Fit Index (CFI), and Root Mean Square Error of Approximation (RMSEA) among goodness-of-fit indices were used for the CFA. When TLI and CFI are 0.90 or higher, it is “acceptable,” [
Known-group validity was verified, and the participants were classified into three groups according to the responses to the PHQ-2 items (group 1: those who responded with “yes” to both of the two items; group 2: those who responded with “no” to any of the two items; and group 3: those who responded with “no” to the two items). Jonckheere-Terpstra test, a nonparametric test, was performed to verify the mean difference between the groups [
Meanwhile, the mean age of the patient group was 55.95 years old, and 39.1% were male and 60.9% were female. The age ranges from 21 to 73. The mean duration of education was 11.39 years. Among them, 8.7% were unmarried, and 73.9% were married. In terms of income level, the proportion of those with income of between KRW 1 million and KRW 2 million was the highest with 26.1%. The proportions of smokers and non-smokers were 52.2% and 47.8%, respectively.
The variables of age, years of education, gender, marital status, income level, and smoking status showed significant differences between the two groups [t (188)=6.55, p<0.001 for age; t (188)=13.25, p<0.001 for years of education; χ2=15.39, p<0.001 for marital status; χ2=15.39, p<0.001 for income level; χ2=15.39, p<0.001 for smoking]. Since the purpose of this study is not a study for verifying the mean difference between the two groups, it is considered to be a study on the reliability and validity of the scale, so it seems that the differences in the demographic data does not have a significant effect on the validation study for the scale.
The results of investigating internal consistency among reliability showed that the Cronbach’s alpha of the K-SSS-8 was 0.85. The verification of test-retest reliability was also found to be suitable (r=0.777, n=31, p<0.001).
First, it was found that factor analysis can be performed through Kaiser-Meyer-Olkin (KMO) values and Bartlett’s test of sphericity [KMO=0.863; χ2 (df=28, n=167)=476.348, p<0.001] [
The number of those who responded with “yes” to both items of the two of the PHQ-2 was 87, accounting for 52.10%. The number of those who responded with “no” to any item of the two was 22, accounting for 13.2%. In addition, the number of those who responded with “no” to both items was 58, accounting for 34.7%. The results of verifying the difference in the total score of K-SSS-8 between the three groups also showed significant difference (for Jonckheere-Terpstra test, J-T statistic=-2.510, p<0.05).
As in previous studies, severity categories were set (a total of 5 categories), and the percentiles according to severity categories are shown in
In this study, the SSS-8 was translated into Korean language for local adaption, the reliability and validity of its Korean version, the K-SSS-8 was verified, and its clinical utility was investigated. The implications of the results are as follows.
First, the reliability analysis revealed that internal consistency and test-retest reliability were reliable. The internal consistency reliability of the K-SSS-8 was slightly better compared to previous studies (Cronbach’s alpha=0.81 in a study by Gierk et al.) [
Next, the results of verifying the goodness-of-fit of the number of factors in the validity analysis showed that the 3-factor model was the most suitable. The explanatory variance explained by the three factors in the 3-factor model was also more than 70%, and the RMSEA value was less than 0.05, indicating “excellent.” [
The first factor was named as “Cardiopulmonary,” and included item #6: “Dizziness,” item #4: “Headaches,” and item #5: “Chest pain or shortness of breath.” In the study of Gierk et al. [
The second factor “Pain” included item #3: “Pain in your arm, legs, or joints,” and item #2: “Back pain.” The second factor literally means physical or body pain, and is thought to be common in patients with physical illness. In the study by Gierk et al. [
Finally, the third factor, “Gastrointestinal and Fatigue” included item #1: “Stomach or bowel problems,” item #7: “Feeling tired or having low energy,” and item #8: “Trouble sleeping.” The third factor is mainly related to physiological symptoms, which are often accompanied by complaints of somatic symptoms. This factor is thought to be closely related to digestive problems, sleep problems, and decreased vitality which are commonly observed in patients with depressive disorder, anxiety disorder, somatic symptoms, and related disorders. It is thought that the third factor enables us to quickly detect the presence or absence of physiological symptoms through the third factor. The third factor includes stomach and fatigue problems. From a psychiatric perspective, these problems are often accompanied by depression and anxiety. Therefore, there may be cognitive and emotional depression and anxiety at the basis of patients with gastrointestinal symptoms and fatigue, and in this case, it is recommended to conduct an additional scale related to depression and anxiety. Unlike Gierk et al. [
In this study, Known-group validity was also verified using a Jonckheere-Terpstra test. According to the participants’ responses (depression) to the PHQ-2, the participants were divided into three groups (group 1: depression-positive for both items; group 2: depression-positive for one item; and group 3: depression-negative for both items). The verification showed that there was a significant difference in the total K-SSS-8 score according to the degree of depression. Similarly, in terms of PHQ-15 and EQ-5D, there was a significance difference in the total scores between the groups. These results suggest that depression may be closely related to the complaint of somatic symptoms [
In addition, frequency analysis according to the severity of the K-SSS-8 was performed for healthy control and patient groups in this study. In the case of the healthy control participants, the proportion of those who had higher than “medium” severity was 43.2%, which is twice as high as in Japan (20.6%) [
In the case of the patient group, the proportion of those who had higher than “medium” severity was 65.1%, unlike the control group, and about 2/3 of the participants in the patient group complained of at least 2–3 somatic symptoms. Diagnostically, more than 90% of them had been diagnosed with depression or anxiety-related disorders, and had no medical abnormalities. It is known that a significant number of patients who complained of somatic symptoms without a medical condition initially visited the internal medicine departments [
Taken together, in terms of clinical utility, the K-SSS-8 can be useful for exploring symptoms such as panic symptoms, physical pain, and physiological symptoms experienced by patients in a short time. In addition, the K-SSS-8 is expected to be very useful for determining the current severity by using the severity categories and for establish additionally required assessment plans for depression and anxiety symptoms. In particular, a K-SSS-8 score of 12 or higher is common in the patient group, but not common in the healthy control group. Therefore, “severe complaints of somatic symptoms” should be considered when establishing treatment plans.
The K-SSS-8 is also thought to be useful in therapeutic aspects. Since the K-SSS-9 was divided into three factors (Cardiopulmonary, Pain, Gastrointestinal and Fatigue), it is thought that it will help to establish a pharmacotherapy or psychotherapy plan based on main symptoms. For example, it is known that the effect size of combined therapy (pharmacotherapy plus cognitive behavior therapy) is high for panic symptoms, and that when physiological symptoms are dominant, it is appropriate to consider pharmacotherapy first [
Lastly, the limitations and future research directions of this study are as follows: First, the factor analysis revealed that the number (n=167) of the participant of this study was within an appropriate range, but it is recommended that the number (n) of participants is more than 200 participants to improve the power of a test [
The online-only Data Supplement is available with this article at
This study was supported by Wonkwang University in 2020.
The authors have no potential conflicts of interest to disclose.
Conceptualization: Sang-Yeol Lee, Jeong Seok Seo, Seung-Ho Jang. Data curation: Sang-Yeol Lee, Kyu-Sic Hwang, Seung-Ho Jang. Formal analysis: Kyu-Sic Hwang, Seung-Ho Jang. Investigation: Chan-Mo Yang, Kyu-Sic Hwang, Seung-Ho Jang. Methodology: Jeong Seok Seo, Seung-Ho Jang. Project administration: Sang-Yeol Lee, Jeong Seok Seo, Seung-Ho Jang. Resources: Jeong Seok Seo, Seung-Ho Jang. Software: Kyu-Sic Hwang, Seung-Ho Jang. Supervision: Jeong Seok Seo, Seung-Ho Jang. Validation: Chan-Mo Yang, Sang-Yeol Lee, Seung-Ho Jang. Visualization: Kyu-Sic Hwang. Writing—original draft: Sang-Yeol Lee, Jeong Seok Seo, Seung-Ho Jang. Writing—review & editing: Sang-Yeol Lee, Jeong Seok Seo, Seung-Ho Jang.
K-SSS-8 items by 3-factor model. K-SSS-8: Korean Version of Somatic Symptom Scale-8.
Participants’ demographic and clinical characteristics
Variable | Group |
Statistic |
|
---|---|---|---|
Normal adults (N=167) | Patient (N=23) | t, χ2 | |
Age, years: mean±SD | 41.67±9.22 | 55.95±13.37 | 6.55 |
Gender, male: N (%) | 39 (23.4%) | 9 (39.1%) | 2.67 |
Education, years: mean±SD | 15.83±0.80 | 11.39 (3.81) | 13.25 |
Marital status, N (%) | 15.39 |
||
Unmarried | 47 (28.1) | 2 (8.7) | |
Married | 116 (69.5) | 17 (73.9) | |
Separated | 1 (0.6) | 1 (4.3) | |
Divorced | 2 (1.2) | 1 (4.3) | |
Lost | 1 (0.6) | 2 (8.7) | |
Income level (₩) | 43.14 |
||
Less than 1.0 million | 1 (0.6) | 6 (26.1) | |
1.0–2.0 million | 56 (33.5) | 6 (26.1) | |
2.0–3.0 million | 61 (36.5) | 3 (13.0) | |
3.0–4.0 million | 23 (13.8) | 5 (21.7) | |
4.0–5.0 million | 21 (12.6) | 1 (4.3) | |
More than 5.0 million | 5 (3.0) | 2 (8.7) | |
Smoking/non-smoking, N (%) | 151 (90.4)/16 (9.6) | 12 (52.2)/11 (47.8) | 24.26 |
p<0.01,
p<0.001.
N: number, SD: standard deviation
Correlation analysis of K-SSS-8 with other somatic symptom scales for the concurrent validity (N=167)
K-SSS-8 | PHQ-15 | EQ-5D | PHQ-2 | |
---|---|---|---|---|
K-SSS-8 | 1.00 | |||
PHQ-15 | 0.857 |
1.00 | ||
EQ-5D | 0.493 |
0.502 |
1.00 | |
PHQ-2 | -0.226 |
-0.171 |
-0.219 |
1.00 |
p<0.05,
p<0.01,
p<0.001.
K-SSS-8: Korean version of Somatic Symptom Scale-8, PHQ-15: Patient Health Questionnaire-15, EQ-5D: EuroQol 5 Dimension, PHQ-2: Patient Health Questionnaire-2
The goodness-of-fit for the 2-, 3-, and 4-factor model by factor analysis solutions
FAS | Model | Cumulative % of variance explained | χ2 | df | TLI | CFI | RMSEA |
---|---|---|---|---|---|---|---|
EFA | 2-factor | 61.67 | 30.348 | 13 | N/A | N/A | 0.0896 |
3-factor | 71.59 | 4.863 | 7 | N/A | N/A | 0.0000 | |
4-factor | 79.52 | 2.317 | 2 | N/A | N/A | 0.0309 | |
CFA | 2-factor | N/A | 35.104 | 19 | 0.948 | 0.965 | 0.0710 |
3-factor | N/A | 10.992 | 17 | 1.022 | 1.000 | 0.0000 | |
4-factor | N/A | N/A | N/A | N/A | N/A | N/A |
FAS: factor analysis solutions, EFA: exploratory factor analysis, CFA: confirmatory factor analysis, TLI: Tucker-Lewis index, CFI: comparative fit index, RMSEA: root mean square error of approximation
EFA pattern matrix of the K-SSS-8 items for the 3-factor model
Item no. | Factor 1: cardiopulmonary | Factor 2: pain | Factor 3: gastrointestinal and fatigue |
---|---|---|---|
06. Dizziness | 0.879 | ||
04. Headaches | 0.681 | ||
05. Chest pain or shortness of breath | 0.514 | ||
03. Pain in your arm, legs, or joints | -0.814 | ||
02. Back pain | -0.744 | ||
01. Stomach or bowel problems | 0.834 | ||
07. Feeling tired or having low energy | 0.585 | ||
08. Trouble sleeping | 0.464 |
EFA: exploratory factor analysis, K-SSS-8: Korean version of Somatic Symptom Scale-8, Factor 1: “Cardiopulmonary,” Factor 2: “Pain,” Factor 3: “Gastrointestinal and Fatigue”
Testing result of known-group validity
Sum of K-SSS-8 | Sum of PHQ-15 | Sum of EQ-5D | |
---|---|---|---|
Group | Group 1, 2, 3 | Group 1, 2, 3 | Group 1, 2, 3 |
J-T statistic | -2.510 | -1.670 | -2.729 |
p | 0.012 | 0.095 | 0.006 |
K-SSS-8: Korean version of Somatic Symptom Scale-8, PHQ-15: Patient Health Questionnaire-15, EQ-5D: EuroQol 5 Dimension, J-T: Jonckheere-Terpstra test
The ratios according to K-SSS-8 severity in each group
K-SSS-8 severity category (range) | Normal adults (N=167) | Patient (N=23) |
---|---|---|
No to minimal (0–3) | 48 (28.7%) | 3 (13.0%) |
Low (4–7) | 47 (28.1%) | 5 (21.7%) |
Medium (8–11) | 38 (22.8%) | 5 (21.7%) |
High (12–15) | 16 (9.6%) | 3 (13.0%) |
Very high (≥16) | 18 (10.8%) | 7 (30.4%) |
K-SSS-8: Korean version of Somatic Symptom Scale-8