Somatic Symptom Scale – 8 (SSS-8)

Abstract

The Somatic Symptom Scale – 8 (SSS-8) is a brief, 8-item, patient-reported outcome measure (PROM) designed to quickly and efficiently assess the burden of common somatic symptoms. Developed primarily by Gierk, Löwe, and colleagues, the SSS-8 serves as a shortened version of the established Patient Health Questionnaire – 15 (PHQ-15). Its initial development was crucial for the DSM-5 field trials, specifically aiding the investigation and classification of the newly established diagnostic category, Somatic Symptom Disorder (SSD). The SSS-8 utilizes a five-point response option and employs a seven-day recall timeframe, differentiating it significantly from the PHQ-15, which uses a three-point option and a four-week timeframe. Initially designated as the PHQ-SSS during the field trials, the instrument was formally renamed SSS-8 to accurately reflect its concise structure and item count (Gierk et al., 2015).

Keywords

Somatic Symptom Scale – 8, SSS-8, Somatic symptom disorder, SSD, PHQ-15, Patient-reported outcome, Somatic symptom burden, Psychometrics, Health care utilization.

Authors

Bernd Gierk, Stefan Kohlmann, Kurt Kroenke, Liane Spangenberg, Martina Zenger, Elmar Brähler, and Bernd Löwe.

Purpose

The primary purpose of the Somatic Symptom Scale – 8 (SSS-8) is to provide a standardized, brief, and reliable measure of somatic symptom burden across diverse populations, including both general community samples and clinical settings.

The instrument is specifically designed to facilitate screening, epidemiological research, and monitoring of symptom severity, particularly in the context of persistent and distressing somatic complaints that may indicate Somatic Symptom Disorder. By offering a concise alternative to longer instruments like the PHQ-15, the SSS-8 improves efficiency in primary care and large-scale survey studies, allowing clinicians and researchers to quickly categorize individuals based on their level of symptom burden (low, medium, high, or very high) and predict associated outcomes, such as health care utilization.

Construct

The SSS-8 measures the psychological construct of Somatic Symptom Burden, defined as the overall severity and frequency of common, medically unexplained physical symptoms experienced by an individual over the past week.

This construct is central to the diagnosis of Somatic Symptom Disorder (SSD) as defined in the DSM-5. The scale focuses on assessing common symptoms (such as pain, fatigue, and gastrointestinal issues) rather than specific disease states. The resulting score is interpreted as a measure of distress and functional impairment related to these physical sensations, which often correlates highly with psychological distress, including measures of depression and anxiety.

Validity

Research has consistently demonstrated that the SSS-8 is a valid measure of somatic symptoms, showing strong evidence of convergent and criterion validity.

In a large survey study (n = 2510), somatic symptom burden as measured by the SSS-8 was significantly associated with several key mental health variables: depression (r = 0.57) and anxiety (r = 0.55). The scale also demonstrated significant inverse correlation with general health status (r = -0.24). Furthermore, the SSS-8 exhibited strong criterion validity regarding health care utilization, with an incidence rate ratio of 1.12, indicating that higher symptom burden reliably predicts increased health service use. A comparison study confirmed that the SSS-8 maintained a comparable pattern of correlations with measures of depression, anxiety, health anxiety, and health-related quality of life (ranging from r=0.32 to 0.61) when compared against the PHQ-15 (Gierk et al., 2015).

Reliability

The SSS-8 possesses good to excellent internal consistency, supporting its reliability as a measure of a single, coherent construct.

In a large-scale population survey (n = 2510), the SSS-8 demonstrated good reliability with a Cronbach’s alpha (α) of 0.81. A subsequent comparison study involving psychosomatic outpatients (n=131) found the reliability of the SSS-8 to be α=0.76. Importantly, the SSS-8 demonstrated high concurrent reliability with its longer predecessor, the PHQ-15, showing a strong correlation between the two scales (r=0.83). These findings confirm that the shortened SSS-8 maintains the psychometric rigor necessary for clinical and research applications.

Factor Analysis

While the source content does not provide specific details on the execution of factor analysis (e.g., Principal Components Analysis or Confirmatory Factor Analysis), the SSS-8 is designed and utilized as a unidimensional measure of overall somatic symptom burden.

The scale’s structure, derived from the 15 items of the PHQ-15, is intended to capture the general severity of physical distress. Its strong internal consistency (Cronbach’s alpha > 0.75) across various samples supports the interpretation that the eight items cohere effectively to measure a single, underlying construct of somatic distress.

Instrument

Test Type: Patient-Reported Outcome Measure (PROM)

Format: Eight self-report items utilizing a 5-point Likert-type response scale.

Language Available: Information not provided in source, but typically developed in German and English, and subsequently translated for international use.

Population Group: General population and clinical samples (e.g., psychosomatic outpatients).

Age Group: Adults.

Population Details: Demonstrated validity in large-scale community surveys (n=2510) and specialized clinical populations (n=131).

Test Methodology: Respondents rate the frequency of experiencing 8 common somatic symptoms over the past seven days. Response options typically range from 0 (“Not bothered at all”) to 4 (“Bothered a lot”). Total scores range from 0 to 32.

The severity categories, calculated based on percentile ranks, are defined as follows:

• No to minimal burden: 0–3 points
• Low burden: 4–7 points
• Medium burden: 8–11 points
• High burden: 12–15 points
• Very high burden: 16–32 points

Keywords

Psychometrics, Somatic symptom burden, SSD, PHQ-SSS, PHQ-15, Health care utilization, Internal consistency, Cronbach’s alpha, Severity categories.

Authors

Author ORCID Identifier: Information not provided in source.

Affiliation Email addresses: Information not provided in source (Affiliations typically include University Medical Center Hamburg-Eppendorf).

Correspondence Address: Information not provided in source.

Permissions & Fee and Test Year

Test Year: 2014 (Based on the publication of the initial validation study in JAMA Internal Medicine by Gierk et al.).

Permissions and Fees: Information regarding specific licensing fees or permissions for clinical use is not provided in the source content. Given the scale’s origin as a tool for the DSM-5 field trials and its relation to the PHQ measures, it may be available for non-commercial research use, but users should consult the primary authors or copyright holders (Löwe, Kroenke, et al.) for commercial application details.

Reference’s

• Gierk, B., Kohlmann, S., Kroenke, K., Spangenberg, L., Zenger, M., Brähler, E., & Löwe, B. (2014). The somatic symptom scale–8 (SSS-8): a brief measure of somatic symptom burden. JAMA internal medicine, 174(3), 399-407.
• Gierk, B., Kohlmann, S., Toussaint, A., Wahl, I., Brünahl, C. A., Murray, A. M., & Löwe, B. (2015). Assessing somatic symptom burden: A psychometric comparison of the Patient Health Questionnaire—15 (PHQ-15) and the Somatic Symptom Scale—8 (SSS-8). Journal of psychosomatic research, 78(4), 352-355.
• Zijlema, W. L., Stolk, R. P., Löwe, B., Rief, W., White, P. D., & Rosmalen, J. G. (2013). How to assess common somatic symptoms in large-scale studies: a systematic review of questionnaires. Journal of psychosomatic research, 74(6), 459-468.

Items of the Somatic Symptom Scale – 8 (SSS-8)

IMPORTANT: The following scale items must be preserved in their original language and must not be changed in any way.

The actual items comprising the Somatic Symptom Scale – 8 were not provided in the source content. The SSS-8 consists of 8 items covering common somatic symptoms, selected from the 15 items of the PHQ-15. These items generally cover pain (e.g., back pain, headache), gastrointestinal symptoms (e.g., stomach pain, constipation), and cardiopulmonary and general symptoms (e.g., trouble sleeping, feeling tired).