Patient Health Questionnaire Somatic Symptom Severity Scale (PHQ-15)

In the mid-1990s the Patient Health Questionnaire (PHQ), was developed and validated as a shorter self-administered version of the Primary Care Evaluation of Mental Disorders (PRIME-MD). The PHQ was developed by Robert Spitzer, Janet Williams and Kurt Kroenke and colleagues at Columbia University. A large study found the PHQ had diagnostic validity comparable to the original clinician-administered PRIME-MD and was more efficient in clinical practice (Spitzer et al., 1999). The Patient Health Questionnaire Somatic Symptom Severity Scale (PHQ-15) is a brief, self-administered questionnaire that was derived from the full PHQ and is increasingly used to assess somatic symptom severity and screen for the potential presence of somatisation and somatoform disorders (based on DSM-IV criteria) in adults (Kroenke et al., 2002). The scale consists of 15 items that ask whether somatic symptoms, such as stomach pain or dizziness are present within the last 4 weeks and the severity (response categories of “not bothered at all”, “bothered a little” and “bothered a lot”). The PHQ-15 scores of 5, 10, and 15 represent cut off points for low, medium, and high somatic symptom severity, respectively (Spritzer et al., 1994).

Psychometric Properties

The PHQ-15 has been validated in different clinical and occupational populations. (De Vroege et al., 2012; Kroenke et al., 2010). With a cut off score of 6 or more the sensitivity of the PHQ-15 was 78% (true positive) and specificity was 71% (false negative). The negative predictive value of 97% indicates that only 3% of individuals who have a score of less than 6 will have a somatoform disorder (Van Ravesteijn et al., 2009). Convergent validity with the Beck Depression Inventory (BDI) and the General Health Questionnaire-12 (GHQ-12) were positive. Increasing scores on the PHQ-15 are strongly associated with increased functional impairment, disability, health care use and symptom-related difficulty (Changsu et al., 2009; Kroenke et al., 2002).  The PHQ-15 demonstrates acceptable internal consistency (Cronbach coefficient alpha of .80) (Kroenke et al., 2002; Van Ravesteijn et al., 2009; Kroenke et al., 1998). The PHQ-15 has moderate test-retest reliability (intraclass correlation coefficient of 0.83) with a 2 week interval (Van Ravesteijn et al., 2009).

The reliability and validity of the PHQ-15 is unaffected by pertinent individual difference factors such as age, gender and education (Kroenke et al., 2010; Kocalevent et al., 2013; Changsu et al., 2009; Shih-Cheng et al., 2016). The PHQ-15 has been translated into over 20 languages (Spritzer et al., 1994). The scale has been validated in Korean and Chinese populations, however does not perform well in Hispanic populations which could be due to multiple factors within the cultural context that may affect how individuals identify and classify bodily sensations, perceive illness and seek medical attention (APA, 2013; Interian et al., 2006; Changsu et al., 2009; Shih-Cheng et al., 2016). East Asian populations often complain of somatic symptoms rather than reveal any depressive feelings, which is important for clinical practice as somatoform disorders have considerable comorbidity with anxiety and depressive disorders which the PHQ-15 does not screen for (Changsu et al., 2009).

Clinical utility

Overall, the PHQ-15 is a valid and reliable screening tool for presence of somatic symptoms and severity. The DSM-IV main criteria for somatoform disorder was medically unexplained symptoms, whereas, the DSM-5 emphasises distress (APA, 2013). Therefore, the PHQ-15 can be aligned with the DSM-5 criteria as the scale is a screening tool of severity and distress (Shih-Chen et al., 2016). More research is needed to support the PHQ-15 as a measure of responsiveness to changes throughout treatment of individuals with somatoform disorders (Kroenke et al., 2010). It is important to note the PHQ-15 is a self-report scale therefore susceptible to reporting biases. Elevated neuroticism or negative affectivity may lead to inflated symptom reporting (Watson et al., 1989). The main strengths of the scale are it is easy to use (for clinician and client), free and has been validated in different clinical and occupational populations. It has shown good sensitivity and specificity for screening for somatoform disorders, however it is not a diagnostic tool rather an indication of an individual at risk (Kroenke et al., 2010). Further, the scale addresses current rather than previous symptoms to gain more valid and reliable data (Kroenke et al., 2010).

Link to free version of PHQ-15


American Psychiatric Association (APA). (2013). Diagnostic and statistical manual of mental disorders: DSM-5. Washington, D.C: American Psychiatric Association.

Spitzer, R., Williams, J., & Kroenke, K. (1994). Instructions for Patient Health Questionnaire (PHQ) and GAD-7 Measures (pp. 1-9). Retrieved from

Spitzer, R., Kroenke, K., & Williams, J. (1999). Validation and Utility of a Self-report Version of PRIME-MD. The Patient Health Questionnaire Primary Care Study Group. JAMA, 282(18), 1737–1744. doi:10.1001/jama.282.18.1737

Kroenke, K., Spitzer, R., & Williams, J. (2002). The PHQ-15: Validity of a New Measure for Evaluating the Severity of Somatic Symptoms. Psychosomatic Medicine64(2), 258-266.

Kroenke, K., Spitzer, R., Williams, J., & Löwe, B. (2010). The Patient Health Questionnaire Somatic, Anxiety, and Depressive Symptom Scales: a systematic review. General Hospital Psychiatry, 32(4), 345-359.

Han, C., Pae, C., Patkar, A., Masand, P., Woong Kim, K., Joe, S., & Jung, I. (2009). Psychometric Properties of the Patient Health Questionnaire–15 (PHQ–15) for Measuring the Somatic Symptoms of Psychiatric Outpatients. Psychosomatics, 50(6), 580-585.

Liao, S., Huang, W., Ma, H., Lee, M., Chen, T., Chen, I., & Gau, S. (2016). The relation between the patient health questionnaire-15 and DSM somatic diagnoses. BMC Psychiatry, 16(1).

Van Ravesteijn, H., Wittkampf, K., Lucassen, P., van de Lisdonk, E., van den Hoogen, H., & van Weert, H. et al. (2009). Detecting Somatoform Disorders in Primary Care With the PHQ-15. The Annals Of Family Medicine, 7(3), 232-238.

Interian, A., Allen, L., Gara, M., Escobar, J., & Díaz-Martínez, A. (2006). Somatic Complaints in Primary Care: Further Examining the Validity of the Patient Health Questionnaire (PHQ-15). Psychosomatics, 47(5), 392-398.

Kocalevent, R., Hinz, A., & Brähler, E. (2013). Standardization of a screening instrument (PHQ-15) for somatization syndromes in the general population. BMC Psychiatry, 13(1).

De Vroege, L., Hoedeman, R., Nuyen, J., Sijtsma, K., & van der Feltz-Cornelis, C. (2012). Erratum to: Validation of the PHQ-15 for Somatoform Disorder in the Occupational Health Care Setting. Journal Of Occupational Rehabilitation, 22(4), 590-590.

Watson, D., & Pennebaker, J. W. (1989). Health complaints, stress, and distress: Exploring the central role of negative affectivity. Psychological Review, 96, 234–254


Somatic Symptom Scale – 8 (SSS-8)

The eight item Somatic Symptom Scale (SSS-8) was recently developed as a brief, patient-reported outcome measure of somatic symptom burden.  The scale assesses common somatic symptoms and is a shortened version of the PHQ-15 questionnaire scale, it was first developed for the DSM 5 field trials that investigated the newly established somatic symptom disorder (Zijlema, 2013). The SSS-8 has a five point response option instead of the three point options for the PHQ-15, and a seven day time frame instead of the four week time-frame for the PHQ-15 Initially called the PHQ-SSS in the DSM 5 field trials it was renamed to shorten it and reflect the number of items (Gierk et al., 2015).

Psychometric properties

Research found the SSS-8 was a reliable and valid measure of somatic symptoms and cut-off scores identify individuals with low, medium, high, and very high somatic symptom burden.

One survey study (n = 2510), identified the SSS-8 to have excellent item characteristics and good reliability (Cronbach α = 0.81). Somatic symptom burden as measured by the SSS-8 was significantly associated with depression (r = 0.57 [95% CI, 0.54 to 0.60]), anxiety (r = 0.55 [95% CI, 0.52 to 0.58]), general health status (r = -0.24 [95% CI, -0.28 to -0.20]), and health care use (incidence rate ratio, 1.12 [95% CI, 1.10 to 1.14]). The SSS-8 severity categories were calculated in accordance with percentile ranks: no to minimal (0-3 points), low (4-7 points), medium (8-11 points), high (12-15 points), and very high (16-32 points) somatic symptom burden. For every SSS-8 severity category increase, there was a 53% (95% CI, 44% to 63%) increase in health care visits (Gierk et al., 2014).

Gierk et al., 2015 did a comparison study between the SSS-8 and the PHQ-15 with psychosomatic outpatients (n=131) and found the reliabilities of the PHQ-15 and SSS-8 were α=0.80 and α=0.76, respectively and both scales were highly correlated (r=0.83). The item characteristics were comparable. There was the same pattern of correlations with measures of depression, anxiety, health anxiety and health-related quality of life (r=0.32 to 0.61). On both scales a 1-point increase was associated with a 3% increase in health care use. The percentile distributions of both scales were similar.



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.



Children’s Somatization Inventory (CSI-24)

The Children’s Somatization Inventory (CSI-24; Walker, Garber, & Greene., 1991) is a revised version from the original Children’s Somatization Inventory conceptualized by Walker and Colleagues in 1991. The original version of the CSI consisted of 35 items corresponding with symptoms consistent with the DSM-III-R criteria for Somatization Disorder. In 2009 the CSI was reviewed and a shorter version, consisting of 24 items, was created. The revised version was the result of eliminating 11 items that were rarely endorsed and had low item-total correlations.
There has been some controversy over the factorial structure of the instrument. Factorial Analysis of the CSI-24 found it not to be considered a strictly uni-dimentional instrument as although its items load onto one factor, with positive standardized factor loadings, the fit was found to be poor (Walker, Garber, & Greene., 1991). Further research has suggested that a 6-item one factor instrument demonstrates a better fit and adequate psychometric properties (Orgiles & Espada, 2013).
The inventory was conceptualized using a predominantly Caucasian clinical sample with a primary complaint of chronic abdominal pain, but this instrument has since been found a valid measure in community populations (Lavigne, Saps, & Bryant., 2012) and other cultures (Orgiles & Espada, 2013)
Psychometric properties
The CSI-24 has been found to correlate highly with the CSI-35 (– r=.99, p<.001; Walker et al., 2009) and hence has been considered a refined version of the original measure. The CSI-35 has been examined in numerous studies and has evidence of high concurrent and convergent validity (r>.4) with other measures of somatization, and good support from a number of studies for it’s construct validity.

  • Internal Consistency alpha .84-.92 (Cerutti et al., 2017; Lavigne, Saps, & Bryant., 2012)
  • Validity for the CSI-24 has been demonstrated in its correlation as expected with measures of anxiety, depression, functional impairment and quality of life (Lavigne, Saps, & Bryant., 2012)
  • Scores for older children and females tend to be higher with a low to medium effect size (d=0.52) (Walker et al., 2009).
  • Parent report has been shown to be lower in school samples and higher in clinical samples than the associated child report (Cerutti et al., 2017).


Cerutti R., Spensieri V., Valastro C., Presaghi F., & Guidetti V. (2017). A comprehensive approach to understand somatic symptoms and their Impact on emotional and psychosocial functioning in children. PLoS ONE, 12(2).

Laird K., Sherman A., Smith C., & Walker L. (2015). Validation of the abdominal pain index using a revised scoring method. Journal Pediatric Psychology, 40(5). Doi:10.1093/jpepsy/jsu118

Lavigne, S.L., Saps, M., & Bryant, F.B. (2012). Reexamining the factor structure of somatization using the children’s somatization inventory (CSI-24) in a community sample. Journal of Pediatric Psychology, 37, 914-924. Doi:10.1093/jpepsy/jss060

Orgiles, M. & Espada, J. P. (2014). Spanish version of the children’s somatization inventory: factorial structure and psychometric properties in a community sample. International Journal of Behavioural Medicine, 21, 556-560. Doi:10.1007/s12529-013-9335-9

Walker, L. S., Beck, J. E., Garber, J., & Lambert, W. (2009). Children’s somatization inventory: Properties of the revised form (CSI-24). Journal of Pediatric Psychology, 34, 430-440.