Depression and anxiety can have very significant effects too, way beyond what people would assume. I spent years thinking I had a serious health disorder, but in the end? Just anxiety causing all the symptoms.
That's not all. We also have "T cell alterations, including exhausted T cells, reduced CD4+ and CD8+ effector memory cell numbers and elevated PD1 expression on central memory cells" which might help narrow it down for the non-believers. I didn't want to post a laundry list, but can post more if necessary.