This might relate to the fact that NAC may also increase exploratory drive in models of depression (Mahmoodzadeh et al., 2021); since the CD2-KO mouse shows features associated with depression, e.g., a lack of neurogenesis (Jaholkowski et al., 2009), the anti-depressant and the hyperactivity-reducing effects of NAC may cancel each other out in this model. This evidence concerns the gene CD2 and major depressive disorder.