“Checklist” with potential reasons for an only alleged resistance to the initial antidepressant medication (“pseudo-resistance”) based on Dold and Kasper (2017)

Is the administered dose of the antidepressant adequate according to the recommendations of the guidelines of the psychiatric societies?
Is the duration of the treatment sufficiently long (at least 2 to 3 wk in the target dose)?
Are the compliance and adherence of the patient concerning the medication intake sufficient? Can noncompliance be ruled out (e.g., by applying plasma level determinations)?
Are adequate drug plasma levels achieved and verified by therapeutic drug monitoring (TDM)? Can metabolic abnormalities in the cytochrome P450 enzyme system probably causing insufficient plasma levels below the therapeutic threshold (e.g., in case of “ultra-rapid metabolizers”) be ruled out?
Is a clinical response maybe masked by the occurrence of adverse effects of the antidepressant medication?
Are relevant psychiatric and somatic comorbidities sufficiently considered, and is it ensured that the depressive disorder is the primary diagnosis?
Are psychosocial stressors probably associated with the depressive symptoms adequately taken into account?