As such, many medical conditions that are associated with an increase in pro-inflammatory cytokine or stress-induced dysregulation of the HPA axis will have increased IDO/kynurenine/AhR activation as an aspect of their pathophysiology, as evident in cancers [9], Alzheimer’s disease [10], depression [11], and arthritis [12], as well as in many other medical conditions. Here, AHR is linked to cancer.