The dominant role of psychosocial risk factors in the development of chronic low back pain disability.

STUDY DESIGN: An inception cohort design was used in which 421 patients were evaluated systematically with a standard battery of psychosocial assessment tests (Structured Interview for DSM-III-R Diagnosis, Minnesota Multiphasic Personality Inventory, and Million Visual Pain Analog Scale) within 6 weeks of acute back pain onset.

OBJECTIVES: The present study evaluated the predictive power of a comprehensive assessment of psychosocial and personality factors in identifying acute low back pain patients who subsequently develop chronic pain disability problems (as measured by job-work status at 1-year follow-up evaluation).

SUMMARY OF BACKGROUND DATA: There has been a relative paucity of prospective research in the United States comprehensively evaluating potential psychosocial risk factors that are associated with those injured workers who subsequently fail to return to work and productivity after 1 year because of low back pain disability. Such research has been quite limited because of the time and cost involved in conducting prospective studies.

METHODS: All study patients were symptomatic with lumbar pain syndrome for no more than 6 weeks. These acute patients were tracked every 3 months, culminating in a structured telephone interview being conducted 1 year after the initial evaluation to document return-to-work status.

RESULTS: Logistic regression analyses, conducted to differentiate between patients who were back at work after 1 year versus patients who were not because of the original back injury, revealed the importance of three psychosocial measures: self-reported pain and disability, scores on Scale 3 of the Minnesota Multiphasic Personality Inventory, and workers' compensation and personal injury insurance status. The model generated correctly classified 90.7% of the cases. Results revealed that major psychopathology, such as depression and substance abuse, did not precede or cause the development chronic pain disability.

CONCLUSIONS: These results show the presence of a robust "psychosocial disability factor" that is associated with those injured workers who are likely to develop chronic low back pain disability problems. Based on these data, a statistical algorithm has been generated that can identify those acute patients who will require early intervention to prevent the development of chronic disability. The second major result is that preinjury or concomitant psychopathology does not appear to predispose patients to chronic pain disability, although high rates of psychopathology have been shown in chronic low back pain. Future research should be directed at emotional vulnerability and psychosocial events in the period after the injury that may lead to chronicity.