In the past ten days, a few different blog entries have been written calling our attention to a meta-analysis that suggests perhaps Cymbalta (duloxotine) — a newer antidepressant — isn’t as good as the company claims it is for the physical symptoms of pain associated with depression.

But, as regular readers of World of Psychology know, a single study does not a conclusion make. Not even a meta-analysis.

The new meta-analysis, conducted by Glen Spielmans, included only five of the published studies that have examined the question of pain, depression and duloxetine (Cymbalta). Why only five, when there have been dozens of studies that have been published examining depression and duloxetine with a pain measure in them?

One key to a good meta-analysis is how is it constructed. An author can choose any set of criteria to include a study in her or his meta-analysis. The criteria can be biased to include only a certain subset of studies that will produce the desired result in the meta-analysis. So a “meta analysis” in and of itself isn’t an indicator of any better science (or quality) than a single study, especially a poorly constructed meta analysis.

I’m not saying this is the case in this particular study. But the new meta-analysis does contradict another meta analysis, which found that some people who took Cymbalta did have reduced pain.

So who’s meta-analysis are we supposed to believe?

Well, until questions like the above are answered, both. Clearly there is a fair amount of evidence that Cymbalta has a positive effect in helping reduce people’s physical pain symptoms (we readily found over a dozen articles in Medline supporting this conclusion). Perhaps that effect isn’t as robust as initially thought (which seems to be so often the case with clinical effects of pharmaceutical drugs), but it seems to be an effect nonetheless (which even the current meta analysis acknowledges).

In the meantime, we’ll let one of the previous meta-analysis findings’ speak for itself:

Improvements in quality of life were significantly greater for both men (p = .006) and women (p = .001) receiving duloxetine than placebo and showed no significant difference by gender.

At the end of the day, isn’t this what’s important about an antidepressant prescribed for depression? That it helps a person relieve their depressive symptoms and improve their quality of life?

Dr. John Grohol is the CEO and founder of Psych Central. He is an author, researcher and expert in mental health online, and has been writing about online behavior, mental health and psychology issues -- as well as the intersection of technology and human behavior -- since 1992. Dr. Grohol sits on the editorial board of the journal Cyberpsychology, Behavior and Social Networking and is a founding board member and treasurer of the Society for Participatory Medicine.

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    Last reviewed: By John M. Grohol, Psy.D. on 2 Jan 2008
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