Depression has been associated with sympathetic nervous system activation and release of neuropeptides (epinephrine, neuropeptide Y), which has a suppressive effect on NK cell activity (Irwin et al. 1991; Maes et al. 1994) by reducing levels of perforin and granzyme B (Dokur et al. 2004). This evidence concerns the gene GZMB and depressive symptom measurement.