Depressive symptoms ( Beck Depression Inventory version II : BDI-II ) , perceived stress ( Perceived Stress Scale : PSS ) , salivary diurnal cortisol rhythms ; inflammatory cytokines ( IL-6 and Tumor necrosis factor - ) , leukocyte phenotype counts , natural killer ( NK ) cell cytotoxicity and lymphocyte proliferation following mitogenic stimulation were assessed at baseline and 6-month follow up .