Outcome switching in research

Vox points to another issue in the evidence-base.

For years, the drug company GlaxoSmithKline illegally marketed paroxetine, sold under the brand name Paxil, as an antidepressant for children and teenagers. It did so by citing what’s known as Study 329 — research that was funded by the drug company and published in 2001, claiming to show that Paxil is “well tolerated and effective” for kids.

That marketing effort worked. In 2002 alone, doctors wrote 2 million Paxil prescriptions for children and adolescents.

Years later, after researchers reanalyzed the raw data behind Study 329, it became clear that the study’s original conclusions were wildly wrong. Not only is Paxil ineffective, working no better than placebo, but it can actually have serious side effects, including self-injury and suicide.

So how did the researchers behind the trial manage to dupe doctors and the public for so long? In part, the study was a notorious example of what’s called “outcome switching” in medical research.

Before researchers start clinical trials, they’re supposed to pre-specify which health outcomes they’re most interested in. For an antidepressant, these might include people’s self-reports on their mood, how the drug affects sleep, sexual desire, and even suicidal thoughts.

The idea is that researchers won’t just publish positive or more favorable outcomes that turn up during the study, while ignoring or hiding important results that don’t quite turn out as they were hoping.

How widespread is the issue?

Well, Dr. Ben Goldacre has a group of medical students reviewing recently published studies in major medical journals.

It’s pretty bad.

Of course, there’s nothing wrong with reporting on unexpected outcomes. I imagine that a lot of hugely important innovations  have come from sharing unexpected findings.

However, I cannot see a reason to not report on the specified outcomes. Withholding “specified” outcomes while sharing new outcomes, for whatever reason, seems like a half-truth and anti-science.

Why would researchers do this, and why would a journal publish it?