It is absolutely with the stigma, people get defensive, because they think CFS is a serious physical illness and not a "mental" one like depression. Like "It's not all in my head, I'm seriously ill, bla bla" well that's the misunderstanding right there, endogenous depression is just as physical as CFS and has many similar biomarkers, genetic, immune, neurological, mitochondrial.
CFS patients can benefit from advance in research of depresion and vice versa as it is a multisystemic illness and absolutely not homogenous. so interdisciplinary research is always beneficial. (Yes also MS, cancer, thyroid etc.) Prof.Dr. de meirleir said that there are as many different cases as there are patients.
Professionals themself admit that the disease is poorly understood still to this date. Heck one doc even said in his book "if you understand ME/CFS, you can understand every disease"
I remain at my standpoint that the two diseases seem to have more in common than some might think.