We cannot conclude whether the treatment‐resistant MDD patients classified in our study are matching with the low‐grade systemic inflammation as reflected by elevated CRP.35 We do not know how much serum sIL‐6R penetrates the blood‐brain barrier, whether sIL‐6R concentrations in the brain and periphery are correlated, or whether they are regulated through the same or similar mechanisms. Here, CRP is linked to major depressive disorder.