In the current issue of P&P there is a report on the role of mood instability as a predictor of outcome in depression. Initial treatment for depression may not result in remission in up to two thirds of patients; therefore, pretreatment predictors of outcomes are important in determining the optimal treatment for each patient.
Previous studies were unsuccessful in predicting under what circumstances distinct treatments have the most optimal effects using patients’ baseline characteristics as moderators. Thus, the present study examined whether changes in the severity of depression during intake may predict treatment outcome.
Patients diagnosed with MDD (n = 156) were randomized to one of three treatment conditions: supportive-expressive therapy (SET; n = 51), antidepressant medication (MED; n = 55) or pill placebo (PBO; n = 50). Depressive symptoms were assessed with the HRSD. The difference between the first and second pretreatment evaluations served as an operationalization of pretreatment changes in depressive symptoms. Treatments were provided for a total of 16 weeks. HRSD assessments throughout active treatment were conducted at weeks 2, 4, 6, 8, 12, 15 and 16 and served as continuous measures of outcomes.
When evaluating whether PT-HRSD instability predicted symptomatic change throughout treatment, Authors found that pretreatment changes in depressive symptoms significantly predicted symptomatic change throughout the course of treatment even after controlling for pretreatment severity of depression. Notably, significant differences in the response to the two active treatments (psychotherapy and medication) versus control were apparent if using pretreatment depression stability as a moderator. Interestingly, the largest effect of pretreatment depressive severity stability on outcomes was in the placebo condition. This suggests that instability of depression at intake is a highly sensitive predictor of the placebo versus medication and psychotherapy responses, and may help determine the magnitude of the placebo effect throughout treatment. Further studies are required in order to validate these findings and examine the underlying mechanism of this association.