The authors regret an omission from the published study methodology. As described in the published manuscript, current treatment with antidepressant medication was an exclusion criterion for the clinical trial whose data were analyzed. We wish to clarify that while current treatment with antidepressant medication was an exclusion criterion, otherwise eligible individuals who were taking ineffective antidepressant medication were allowed to sign consent and participate in the study so long as they completed a study-supervised taper and discontinuation of the medication prior to beginning the study medication. Of the 108 randomized participants in this publication, 30 individuals completed a study-supervised taper and discontinuation of ineffective antidepressant medication prior to randomization.
Our judgment is that this additional methodological information does not affect the validity of the results presented. It was always our intention, as described in the original grant application, to offer study participation to individuals taking an ineffective antidepressant medication so long as they underwent a study-supervised medication taper. It was not the case that we wished to avoid enrolling such individuals or that we expected such past treatment to impact the study results. To the contrary, the exclusion criterion stemmed from the research design consideration that we wished for all participants to be assigned to the same new study medication (or placebo) as they began the study. Moreover, we note that the internal validity of the study is protected by randomization and the quality of the measurements performed in the study at baseline and across time, not by the specific characteristics of the enrolled participants. In this case participants who had a study-supervised taper and discontinuation of medication were evenly assorted across the two study arms (16/30 tapered participants assigned to the Open Group; 14/30 tapered participants assigned to the Hidden Group).
In addition, we note that we never planned to analyze individuals receiving a study-supervised taper differently or to conduct subgroup analyses regarding tapered vs. non-tapered individuals. We do not have specific hypotheses regarding such an analysis and are unclear what the results would indicate. Since the nature of the study population influences the external validity of study results, our primary motivation here is to ensure AJGP readers have a comprehensive knowledge of our study population to facilitate their accurate understanding of to whom the results generalize.
The authors would like to apologise for any inconvenience caused.
Footnotes
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