Individual variability in treatment response to antidepressants in major depression: comparing trial-level and patient-level analyses.

In treatment trials, as well as in clinical practice, a number of individuals with depression fail to respond to medications with established antidepressant properties. The presence of such non-responders has been considered as indicative of inter-individual variability in treatment responsiveness, but disparate outcomes between individuals could also be due to other factors, such as inter-individual differences in disease severity and spontaneous improvement (1). To address this issue, recent studies (1,2) have compared variability (specifically standard deviations, SDs) between groups administered active treatment and placebo across trials. When no differences in variability have been found, this has been quoted as an argument against antidepressants being effective or against the value of precision medicine in depression (1).