Antidepressant medications likely provide little or no benefit to people with mild or moderate depression, a new study has found. Rather, the mere act of seeing a doctor, discussing symptoms and learning about depression probably triggers the improvements many patients experience while on medication.
Only people with severe depression receive additional benefits from drugs, said the senior author of the study, Robert J. DeRubeis, a University of Pennsylvania psychology professor. The research was released online Tuesday and will be published today in the Journal of the American Medical Association.
Hundreds of studies have attested to the benefits of antidepressants over placebos (taking a sham pill without knowing that the pill has no active ingredient), DeRubeis said. But many studies involve only participants with severe levels of depression. Confusion arises, he said, “because there is a tendency to generalize the findings to mean that all depressed people benefit from medications.”
The current analysis attempted to quantify how much of the benefit of antidepressants is attributable to actual chemical effects on the brain and how much can be explained by other factors, such as visiting a doctor, taking action to feel better or the mere passage of time.
Researchers reviewed six randomized, placebo-controlled studies with a total of 718 patients who took either an antidepressant or a placebo. The patients were adults with levels of depression ranging from mild to very severe based on the Hamilton Depression Ratings Scale, a questionnaire widely used in depression research. Researchers then compared the patients’ depression scores at the beginning of treatment and after at least six weeks of treatment.
The study found that the magnitude of the drugs’ benefit increased with the baseline level of depression. The effect of treatment was similar in people with mild, moderate and severe symptoms, regardless of whether they took an antidepressant or placebo. Only the people who rated very severe on the depression measurement at the start of the study showed measurable improvements after taking antidepressants.
“There is no doubt that there are tremendous benefits from antidepressants, as our study showed,” DeRubeis said. “But this study helps us resolve, to some degree, the question of how much benefit people can expect from the medicines themselves when symptoms are not severe.”
Other research has also found that antidepressants are most effective for severe symptoms, said Dr. Philip Wang, deputy director of the National Institute of Mental Health.
Of the six studies in the current meta-analysis, three involved SSRI medications, the most commonly used antidepressants today, and three involved an older class of medications called tricyclics. Both classes are thought to be equally effective although SSRIs are associated with fewer side effects.
One exception to the study findings, DeRubeis said, was for people with dysthymia, or chronic, low-level depression. The current analysis assessed severity of symptoms, not chronicity, DeRubeis said. Other studies have established that people with chronic depression, no matter how severe, tend to respond well to antidepressants while other treatment may be ineffective.