AHR and major depressive disorder: Nonetheless, in light of evidence for a role the AHRR in atherosclerosis36,37 and PTSD31,32 in human studies, in conjunction with evidence from animal studies implicating dysfunction of the AHRR’s target—the aryl hydrocarbon receptor—in aging (notably, brain aging)38 and neuroinflammation39, the AHRR remains an interesting and worthwhile target for further research in depression and other psychiatric diseases.