HCRTR2 and major depressive disorder: The selective OX1Rantagonist was chosen to treat the animals and was unexpectedly found to cause depressive symptoms in control animals[49]; The expression of OX2R in their hypothalamus was found to be lower in mice with depressive symptoms.[50] A study evaluating the level of OXA in cerebrospinal fluid found a significant decrease of OXA in cerebrospinal fluid of patients with major depressive disorder as well as some patients who attempted suicide due to major depression compared to healthy individuals (P < .01).[51]