Low-back-pain related disability: an integration of psychological risk factors into the stress process model.

The purpose of this study was to verify the usefulness of an adaptation of the stress process model in organizing the psychological variables associated with the development of low-back-pain related disability. French-speaking Canadian workers on compensated sick leave (N=439) due to recent occupational low back pain (LBP) were evaluated during the sub-acute stage of LBP (between 30 and 83 days after injury). They were assessed for the following factors: life events, injury-specific cognitive appraisal, emotional distress, avoidance coping, and functional disability. Confirmatory factor analyses were used to test and modify the measurement model. An important modification in the measurement model was the association of catastrophizing with the emotional distress factor. During the sub-acute stage, path analyses revealed a satisfactory fit of the following model (the following coefficients are standardized): (a) life events (.30) and cognitive appraisal (.42) explained emotional distress (r(2)=.30); (b) emotional distress (.42) and cognitive appraisal (.36) explained the use of avoidance coping (r(2)=.45); and (c) emotional distress (.24) and avoidance coping (.56) explained functional disability (r(2)=.53). The stress model tested here reaffirms the importance of life events in the development of disability through the more established emotional distress factor. Also, cognitive appraisal appears to have an indirect effect on disability through activity avoidance and distress. This adaptation of the stress model makes it possible to integrate risk factors into a reduced set of meaningful factors and proposes a more general adaptation explanation of disability than the specific fear-avoidance model.