Examining Pain Subgroups One and Five Years After Spinal Cord Injury: The Importance of Depression in Chronic Pain.

OBJECTIVE

This study aimed to (1) replicate pain/depression clusters among individuals with spinal cord injury (SCI) as found by Wilson et al. (Rehabil Psychol. 2005; 50(4): 381-8, doi:10.1037/0090-5550.50.4.381); (2) examine demographic differences among pain/depression clusters 1 (Y1) and 5 (Y5) years postinjury; and (3) predict evolution to Chronic Pain Syndrome (CPS) subgroup at Y5.

DESIGN

Observational; longitudinal.

SETTING

Data from the Spinal Cord Injury Model Systems National Database.

PARTICIPANTS

Persons with traumatic SCI Y1 (n=5924) and Y5 (n=3349) postinjury.

INTERVENTIONS: None.

MAIN OUTCOME MEASURES: Pain/depression clusters based on pain intensity (0-10 Numeric Rating Scale), pain interference (Medical Outcomes Survey-Short Form-12 item), and depression (Patient Health Questionnaire-9 item).

RESULTS

A 4-subgroup solution consistent with prior literature was retained at Y1 and Y5 given its clinical relevance: Low Pain (low pain intensity, interference, and depression), Positive Adaptation to Pain (high pain intensity, low pain interference and depression), Minimal Distress (high pain intensity and interference, low depression), and CPS (high pain intensity, interference, and depression). The proportion in the CPS cluster increased from Y1 (11%) to Y5 (16%). Those with Black/African American race, less than high school education, or violent injury etiology were overrepresented in the CPS subgroup at Y5. Higher Y1 depression (odds ratio [OR], 1.69; 95% confidence interval [CI], 1.36-2.08) and incomplete injury (OR, 2.07; 95% CI, 1.46-2.96) were associated with increased odds of evolving to CPS at Y5; Y1 pain intensity and interference were not associated with odds of evolving to CPS at Y5 (P>.1).

CONCLUSIONS

The pain/depression subgroups identified by Wilson et al. (2005) remain clinically relevant in a contemporary SCI sample. Depression, even at subclinical levels, is a stronger predictor of future development of CPS than pain intensity or interference. Findings highlight the importance of early depression screening among individuals with SCI.