Prof. Dr. Michael Maes is a highly cited international scientist and author (H-index>137) who has published more than 900 scientific papers in international journals. Dr. Maes is mentioned by the Bibliometric Website Expertscape (objective ranking of medical expertise) as worldwide: #1 in CFS; #1 in oxidative stress; #1 in encephalomyelitis; #1 in nitrosative stress; #1 in nitrosation; #1 in tryptophan; #2 in bacterial translocation; #3 in stress, physiological; #3 in inflammation; #2 in neuroimmune; #5 in depression; #4 in fatigue; #5 in psychiatry; #6 in depressive disorder; #7 in melancholia; #8 in affective disorders; and #8 in mood disorders. The work of Dr. Maes covers phenomenological aspects of mood disorders and the supra-multi-disciplinary field of “pathway and drug discovery processes” in depression, bipolar disorder, schizophrenia, ME/CFS, and more particularly the immune–inflammatory pathways and its connections and sequels. Dr. Maes discovered that “clinical depression” is a systemic illness characterized by peripheral a) increases in proinflammatory cytokine levels, an acute phase response; b) cell-mediated immune (CMI) activation; c) lowered omega-3 PUFA levels; d) lower plasma tryptophan in depression, which determines brain serotonin contents, as an inflammatory sequel, and that IFNα-induced depression is associated with IDO activation, which is accompanied by increased synthesis of neurotoxic tryptophan catabolites.