To the Editor,
We have read the letter by Rus and Kooij [1] regarding our study of COVID-19-related mortality among selective serotonin reuptake inhibitor (SSRI) users with great interest and we thank Rus and Kooij for their interest in our study [1,2]. The main claim by Rus and Kooij [1] is that psychiatric comorbidity and lifestyle factors could contribute to residual confounding in our study. These limitations are already acknowledged and discussed in our article, but we appreciate the opportunity to explain our considerations in further detail [2]. It is difficult for us to go into detail with the long list of psychiatric conditions mentioned by Rus and Kooij, as the references citated by Rus and Kooij only cover a few and often severe degrees of the conditions [1]. When performing our study, we had thorough considerations regarding psychiatric comorbidity and identified psychotic disorders and mood disorders as relevant conditions with solid evidence in the literature. However, when keeping the indication and prescription practice of SSRI medications in mind, we found it best only to incorporate adjustment of psychotic disorders in our analysis.