Assessment of chronic back pain patient characteristics using factor analysis of the MMPI-2: which dimensions are...

Guided by the study of Deardorff et al. (Pain, 54 (1993) 153-158), the MMPI-2 data from 240 chronic back pain patients were factor-analyzed in an attempt to discern the most important dimensions for this patient population. Principal components analysis with an oblique rotation revealed four underlying factors: Psychological disturbances, Extraversion-introversion, Passivity, and Somatic complaints. The factor structure reported by Deardorff et al. was thus successfully replicated. The stability of the factors was also supported using random split subsamples. External measures relevant to pain were used to investigate the external validity of Somatic complaints in a subsample of patients (n=93). Relations were found to number of painful sites, Waddell signs, fear of movement (maximal isometric flexion and extension performance by dynamometry, and cardiovascular fitness (VO2-max). Substantial differences emerged across genders. The derived MMPI-2 dimensions appear to constitute important characteristics associated with chronic pain. It is concluded that MMPI-2 research into chronic pain may become more productive when the instrument and its clinical correlates are examined within a clear conceptual framework of distress and personality relevant for chronic pain and its treatment.