Orexin OX2 receptor agonists have demonstrated the ability to enhance wakefulness in rodent models, as well as in nonhuman primates and patients with narcolepsy and idiopathic hypersomnia. Based on recent findings, it has been hypothesized that they may also regulate cognition, mood and other neuropsychiatric functions. Furthermore, dysregulated orexin signaling has been reported in patients with major depressive disorder (MDD) with suicide attempts.