Table 2.
Pattern of factors after rotation in explanatory factor analysis using the baseline data.
| Items (QIDS-SR16 and SSI pain-related items) | Factors | |||
|---|---|---|---|---|
| Factor I | Factor II | Factor III | Factor IV | |
| 1. Sleep onset insomnia | 0.04 | 0.72 | 0.10 | -0.01 |
| 2. Mid-nocturnal insomnia | -0.01 | 0.72 | 0.004 | 0.08 |
| 3. Early morning awakening | 0.06 | 0.67 | -0.14 | 0.03 |
| 4. Hypersomnia | 0.38 | -0.34 | -0.20 | 0.07 |
| 5. Feeling sad | 0.68 | -0.01 | 0.13 | -0.01 |
| 6+7. Appetite disturbance | 0.17 | 0.01 | 0.71 | 0.000 |
| 8+9. Weight disturbance | 0.04 | -0.02 | 0.77 | 0.06 |
| 10. Concentration/decision-making | 0.74 | 0.06 | 0.01 | -0.03 |
| 11. Self-criticism and blame | 0.49 | 0.03 | 0.17 | 0.02 |
| 12. Suicidal thoughts | 0.26 | 0.09 | 0.34 | 0.07 |
| 13. Interest in people/activities | 0.69 | -0.01 | 0.12 | -0.04 |
| 14. Energy/fatigability | 0.76 | 0.03 | 0.04 | 0.004 |
| 15. Psychomotor retardation | 0.61 | 0.12 | -0.08 | 0.07 |
| 16. Psychomotor agitation | 0.29† | 0.19 | 0.07 | 0.01 |
| 17. Muscle soreness | 0.03 | 0.01 | -0.05 | 0.80 |
| 18. Abdominal pain | -0.21 | 0.02 | 0.20 | 0.64 |
| 19. Lower back pain | 0.09 | -0.06 | 0.02 | 0.70 |
| 20. Heart/chest pain | -0.05 | 0.06 | 0.23 | 0.54 |
| 21. Joints pain | -0.06 | 0.03 | 0.01 | 0.74 |
| 22. Neck pain | 0.23 | -0.11 | 0.01 | 0.70 |
| 23. Headache | 0.15 | 0.08 | -0.11 | 0.55 |
| Interpretation | Mood/ cognitive |
Sleep disturbance | Appetite/ weight disturbance |
Pain |
Note 1: Bolded items indicate major loadings for each item, which were finally loaded onto the factors based on their loading values (i.e., an absolute value of >0.3) and clinical judgement.
Note 2: Item 1-16 are the items included in the 16-item Quick Inventory of Depressive Symptomatology Self-Report (QIDS-SR16), and Item 17-23 are the seven pain-related items of the Somatic Symptom Inventory (SSI). Factor analysis was performed with a total of 21 items (item 6 and 7 as well as item 8 and 9 were combined into one item, respectively).