Not sad enough for a depression trial? A systematic review of depression measures and cut points in clinical trial registrations.

Introduction: Patient reported outcomes are central to the evaluation of behavioral, drug, or somatic interventions focusing depression. Continuous measures are mostly interpreted with cut points that serve as inclusion criteria and define remission. The present review provides an overview of measures (BDI; BDI-II; CESD; HADS; HAMD-17; MADRS; PHQ-9; QIDS) and cut points in clinical trials on depression and tests for systematic differences concerning varying types of interventions.

Methods: We analyzed 2632 trials registered via clinicaltrials.gov registered between 2000/01/01 - 2019/12/31 that used one or more pre-specified measures of depression of which 1600 reported cut points for either inclusion of participants or the definition of clinical remission.

Results: The included studies more often used clinician-administered scales than self-report questionnaires as criterion for the inclusion of study participants and for the definition of clinical remission. Clinician administered scales are dominating in drug trials, while self-report questionnaires are primarily used in behavioral trials. This trend accelerated during the last 20 years. Compared to studies on behavioral therapies, studies with drug or other interventions used higher cut points to include patients. Comparisons between the interventions revealed highly significant differences in the used cut points of MADRS, HAMD-17 and PHQ-9.

Conclusions: Choice of measure and cut points is an important aspect of trial design and should be homogenized in order to make trials of different types of interventions more readily comparable. Similarly, systematic differences between treatment types in how patients are included and how remission is defined also hamper the comparisons between different treatment modalities.