TNF and depressive symptom measurement: TNF-α still had a positive correlation with depression (Beta = 0.23, p = 0.024) in the multivariate model after further adjusting for 6MWD, FEV1%, and pack/years, as shown in table 3 (Module 2); this model explained 15.6% of the variance in depression scores where TNF-α alone contributed with 5%.