Haas et al. [56] found that there were no significant differences in BDNF levels between patients taking no antidepressant treatments, patients taking analgesic doses of antidepressants, and patients taking antidepressants at therapeutic doses for depression (in pg/mL: group 1 = 130.4 ± 106.2; group 2 = 146.6 ± 137.9; group 3 = 194.0 ± 210.3, p-value = 0.81). The gene discussed is BDNF; the disease is depressive disorder.