When heterozygous Bdnf null (Bdnf+/−) mice were employed to assess BDNF’s role in the antidepressant response, a ~50% reduction in BDNF levels did not impact depression-related behavior per se, but the antidepressant imipramine was ineffective in the forced swim test [17]. The gene discussed is BDNF; the disease is major depressive disorder.