Course of TNF-α serum level, pain intensity and depression score during six months' follow-up. The two patient groups showed no differences in TNF-α serum level or pain intensity at any time point. Patients with depression showed significantly higher CES-D values than those without depression at t0 (P < 0.001) and t2 (P < 0.001), but not at t3 (P > 0.05). All three parameters were significantly lower at t2 and t3 than at t0, with the exception of CES-D at t3 in patients with isolated cLBP. n.c. = not collected. *: differences between patient groups (*** = P < 0.001); #: comparison of T1, T2 and T3 each vs T0 (### = P < 0.001, ## = P < 0.01; # = P < 0.05).