Longitudinal relationships between anxiety, depression, and pain: results from a two-year cohort study of lower extremity trauma patients.

Previous studies have shown that pain, depression, and anxiety are common after trauma. A longitudinal relationship between depression, anxiety, and chronic pain has been hypothesized. Severe lower extremity trauma patients (n = 545) were followed at 3, 6, 12, and 24 months after injury using a visual analog "present pain intensity" scale and the depression and anxiety scales of the Brief Symptom Inventory. Structural model results are presented as Standardized Regression Weights (SRW). Multiple imputation was used to account for missing data. A single structural model including all longitudinal pain intensity, anxiety symptoms, and depression symptoms time-points yielded excellent fit measures. Pain weakly predicted depression (3-6 months SRW = 0.07, P = .05; 6-12 months SRW = 0.06, P = .10) and anxiety (3-6 months SRW = 0.05, P = .21; 6-12 months SRW = 0.08, P = .03) during the first year after injury, and did not predict either construct beyond 1 year. Depression did not predict pain over any time period. In contrast, anxiety predicted pain over all time periods (3-6 months SRW = 0.11, P = .012; 6-12 months SRW = 0.14, P = .0065; 12-24 months SRW = 0.18, P < .0001). The results suggest that in the early phase after trauma, pain predicts anxiety and depression, but the magnitude of these relationships are smaller than the longitudinal relationship from anxiety to pain over this period. In the late (or chronic) phase after injury, the longitudinal relationship from anxiety on pain nearly doubles and is the only significant relationship. Despite missing data and a single item measure of pain intensity, these results provide evidence that negative mood, specifically anxiety, has an important role in the persistence of acute pain.