In contrast to the previously observed less-depression-like behavior of the ClockΔ19 mutant mice (Roybal et al. 2007), the CLOCK knock-down mice exhibited increased depression-like behavior in the forced swim and learned helplessness test and thereby express a mixed state of mania- and depression-like behavior (Mukherjee et al. 2010). The gene discussed is CLOCK; the disease is depressive disorder.