In males, a significant increase in plasma hypocretin-1 levels was found in MDD 60.51 (35.79–80.12) pg/ml) and BD [65.40 (58.76–74.14) pg/ml] patients compared to controls [45.63 (28.51–62.05) pg/ml], and BD patients had higher hypocretin-1 levels than MDD patients (all P < 0.016, Figure 2A). Here, HCRT is linked to major depressive disorder.