## Factor Structure

### AEQ - Affective responses

Out of 12 affective items of the original KPI, which are related to FAR or ER, one item was excluded as it focused more on somatic complaints than on affective (“tired/exhausted”) one other item due to double factor loading. A PCA of 10 items with oblique rotation revealed a clear 2-factor solution with eigenvalues exceeding one. Together, these factors accounted for 71.8 % of the total variance. Factor I (Anxiety/Depression ADS) accounted for 60.7% of the variance and factor II (Positive Mood despite pain PMS) for 11.1%.

### AEQ - Cognitive responses

A PCA of 16 items revealed a clear 3-factor solution with eigenvalues exceeding one. Together, these factors accounted for 62.9 % of the total variance. Factor I accounted for 37.6% of the variance, factor II for 14.6%, and factor III for 10.7% (see table 3). The resulting scales were labeled as Help-Hopelessnes Scale (HHS), Catastrophizing Thoughts Scale (CTS) and Thought Suppression Scale (TSS).

### AEQ - Behavioral responses

A PCA of 23 items revealed 4 factors that accounted for 61.9% of the total variance. Factor I accounted for 36.2% of the variance, factor II for 11.2%, factor III for 7.9% and factor IV for 6.6%. Factor I comprised items regarding avoidance of social activities and factor II avoidance of physical activities . The assigning of items to these both factors was identical with the original scales of the KPI. Factor III was created by items referring to humor in spite of pain and distraction as responses to pain, whereas factor IV comprised items representing the trial of pain persistence (e.g. “I take care not to let myself go”). This result was different compared to the original KPI Behavioral Endurance Scale, which covered both sets of items. The resulting AEQ scales were labeled as Avoidance of Social Activities Scale (ASAS), Avoidance of Physical Activities Scales (APAS) and Behavioral Endurance Scale (BES) with the two sub-scales Humor/Distraction Scale (HDS) and Pain Persistence Scale (PPS).