In the U.S., antidepressants are used by nearly 15 million adults every year. Many of these patients fall into the mild or moderately depressed category, yet few studies have been conducted on the effectiveness of antidepressants on such patients. Most studies – including those used to assess a drug’s safety and effectiveness prior to approval – focus on severely depressed patients.
According to the JAMA study, in many cases, antidepressants were no more effective in treating people with mild depression than placebos. The study combined the results of six studies, comparing a total of 718 patients assigned an antidepressant or a placebo. Three of the studies looked at Paxil and the others looked at imipramine, an older antidepressants.
According to the Hamilton Depression Rating Scale, which doctors use to diagnose depression, severity of the depression suffered by patients in the study ranged from mildly depressed to very severely depressed. On that scale, severely depressed patients score over 23.
The study found that patients taking Paxil or imipramine who had scored under 23 on the Hamilton scale improved by just one point more than those given a placebo. In patients with scores of 18 or less, indicating mild or moderate depression, the difference between both groups was less than one point.
Patients with severe depression did do better, improving an average of four points more on the rating scale than similar patients taking a placebo. This difference was deemed significant.