Worse off by waiting for treatment? The impact of waiting time on clinical course and treatment outcome for depression in routine care

Long-term untreated major depressive disorder (MDD) is associated with a less favorable clinical course. Waiting time, defined as the interval between diagnostic workup and treatment initiation, may be clinically relevant given the prolongation of the pre-existing duration of untreated MDD. However, it is currently unknown whether and to what extent waiting time affects treatment course in routine outpatient care. Retrospectively extracted data from 715 outpatients with MDD who received naturalistic outpatient MDD treatment were examined. Treatment outcome was defined as the difference in depression severity at the start of treatment and six months thereafter. Clinical course during waiting time was defined by the difference in severity at diagnostic workup and at treatment initiation. We analyzed the association between waiting time and treatment outcome and between waiting time and clinical course during this waiting time using multivariable regression analyses. We adjusted for severity and suicidality as potential confounders. An increased duration of the waiting time was associated with a less favorable treatment outcome (B = 0.049, SE = 0.019, p = 0.01). This association persisted after adjustment for potential confounders (B = 0.053, SE = 0.02, p = 0.01). No association was found between length of waiting time and clinical course during waiting time. Strict definitions resulted in smaller sample sizes for the final analyses. The uncontrolled design may be questionable to definitively establish the impact of waiting time on treatment outcome. A prolonged waiting time is significantly associated with less favorable treatment outcome. Reduction of waiting time deserves priority in depression treatment planning to improve clinical outcomes. •A longer waiting time was significantly associated with a worse treatment outcome.•This association persisted after adjustment for potential confounders.•Clinical course during waiting time was not associated with duration of waiting time.•Minimizing waiting times should be a priority to improve MDD treatment outcomes.