We analysed data from MINocycline in DEPression, a 4-week, randomized, placebo controlled (1:1) trial of minocycline added to antidepressant treatment in 39 TRD patients (n = 18 minocycline; n = 21 placebo) with C-reactive protein (CRP) ⩾1 mg/L. Here, CRP is linked to treatment resistant depression.