Handling clinical comorbidity in randomized clinical trials in psychiatry.

The purpose of this paper is to a) outline the importance of including patients with clinical comorbidities in Randomized Clinical Trials (RCTs) of psychiatric treatments; and b) to propose a specific approach for best handling, analyzing and interpreting the data on clinical comorbidities in terms of their impact on treatment outcomes. To do this we first define and describe clinical comorbidity and differentiate it from other forms of comorbidity. We then describe the methodological and analytical problems associated with excluding patients with clinically comorbid conditions from RCTs, including the impact on the outcomes of RCTs in psychiatry and the impact on evidence-based clinical decision-making. We then address the challenges inherent to including patients with clinical comorbidities in RCTs. Finally, we propose a methodological and analytic approach to deal with these issues in RCTs which aims to significantly improve the information yielded from RCTs in psychiatry, and thus improve clinical decision-making.