Introduction: While the short-term response rates to antidepressant medication and placebo are well established, very little is known about the short-term course of untreated depression. Knowledge of the course of untreated depression can serve as a benchmark for assessing the true benefits of active treatment.
Method: A meta-analysis was performed analyzing the outcomes of all psychotherapy studies that randomized adult outpatients with major depressive disorder to a wait-list control group.
Results: Nineteen studies involving 221 subjects were reviewed. The mean decrease in Hamilton Rating Scale for Depression scores over 2-20 weeks was 11.9%, while the mean decrease in Beck Depression Inventory scores was 15.7%. Using a subsample of studies that reported individual outcomes, we estimated that 15 of 76 subjects (19.7%) improved to a degree comparable to what would be considered a positive response in antidepressant trials.
Conclusions: In the short-term, depressive symptomatology can be expected to decrease by about 10-15% on average without treatment. As many as 20% of subjects who participate in a short-term antidepressant trial may experience a spontaneous remission.