BACKGROUND: Depression and inflammation are intertwined, which is particularly relevant for patients with lung cancer who have an abundance of inflammation and experience depression. Acute phase reactants (APRs), albumin and C-reactive protein (CRP), are easily interpretable indirect markers of inflammation that have never been concomitantly compared with depression. Inflammation increases CRP (positive APR) and decreases albumin (negative APR). We hypothesize that albumin will be similarly associated with depression, thereby helping to inform the diagnosis of inflammatory depression.
OBJECTIVE: Compares the relationship between depression and representative positive and negative acute phase reactants in patients with metastatic lung cancer.
METHODS: Patients (n = 109) with metastatic lung cancer were evaluated for depression using the Hospital Anxiety and Depression Scale. Inflammation as measured by positive (CRP) and negative (albumin) APRs along with demographic and treatment variables were analyzed for associations with depression.
RESULTS: Depression was associated with lower albumin (r = -0.35, P < 0.001), higher CRP (r = 0.47, P < 0.001), and the CRP/albumin ratio (r = 0.45, P < 0.001). Hierarchical linear regression modeling found that albumin was associated with depression when controlling for demographics, disease, and treatment types (β = -0.28, P = 0.01). When both APRs were in the model, only CRP predicted depression (β = 0.31, P = 0.01), and albumin did not moderate CRP and depression. CRP/albumin ratio did not add to understanding depression variability, but patients with both low albumin and high CRP had particularly severe depression.
CONCLUSION: Albumin is associated with depression but not to a greater extent than CRP. The coupling of lower albumin and higher CRP describes more severe depression. Positive and negative APRs may form a distinct biologic signature to help identify patients with inflammatory depression in the lung cancer setting.
