The Physical Symptom Scale-8: Psychometric Characteristics of a Short- Form Version of the PHQ-15 and its Use in TMD-Related Assessment and Research

Aims: To describe the development of the Physical Symptom Scale-8 (PSS-8) and to examine its psychometric properties and use in temporomandibular disorder (TMD)-related assessment and research. Methods: An online survey comprising demographic variables, the DC/TMD pain screener (TPS), Short-Form Fonseca Anamnestic Index (SFAI), PSS-8, PHQ-15, and Depression, Anxiety, and Stress Scale-21 (DASS-21) was administered to young adults attending a technical college. The PSS-8 adopted the Somatic Symptom Scale-8 (SSS-8) items but maintained the 3-point response scale and 4-week time frame of the PHQ-15. Internal consistency and reliability of the PSS- 8 were determined by its Cronbach alpha value. Known-groups and concurrent/convergent validity were examined using Mann-Whitney U test and Spearman correlation (alpha =.05), respectively. Results: Responses from 400 participants (mean age 18.8 +/- 1.5 years; 52.3% women) were evaluated. Pain-related (WPT) and all (WAT) TMDs were present in 8.5% and 17.3% of the sample, respectively. The PSS- 8 exhibited good internal consistency (alpha = 0.82) and sound known-groups validity, with the WPT/WAT groups having significantly higher PSS-8 scores than those without TMDs. Good concurrent and convergent validity were also observed, with moderate to strong correlations with the PHQ-15 (rs = 0.97) and DASS-21 scores (rs = 0.48 to 0.60). Correlations with the TPS and SFAI scores were weaker (rs = 0.28 to 0.34). Conclusion: The PSS-8 presented good psychometric properties and performed similarly to the PHQ-15. It holds promise as the "de facto" shortened version of the PHQ-15 for TMDs and related work.