Effect of antidepressants exaggerated due to buried data

The New England Journal of Medicine has just published a study that found the effectiveness of 12 of the most popular antidepressants has been exaggerated because pharmaceutical companies have been ‘hiding’ data from negative drug trials.

Known as the ‘file drawer effect‘, it involves submitting only positive results to be published in scientific journals.

This type of selective publishing was recognised as a pervasive problem in medicine, and to try and combat this, a rule was introduced that required all clinical trials to be registered before they began.

This means no-one could claim that a negative study didn’t occur and others could try and track down the data if needed.

The researchers in this new study decide to do exactly this. They examined the American Food and Drug Admistration (FDA) register and requested data from all 74 trials of the most commonly used antidepressant drugs.

They then compared the results from all the trials, to just the trials that had been published in the medical literature.

The findings are quite shocking:

A total of 37 studies viewed by the FDA as having positive results were published; 1 study viewed as positive was not published.

Studies viewed by the FDA as having negative or questionable results were, with 3 exceptions, either not published (22 studies) or published in a way that, in our opinion, conveyed a positive outcome (11 studies).

According to the published literature, it appeared that 94% of the trials conducted were positive. By contrast, the FDA analysis showed that 51% were positive.

In other words, when all the studies are examined, there’s only about 50-50 chance that a scientific study of an antidepressant drug will find it more effective than placebo in treating depression.

The Wall Street Journal has a good write-up of the study, from which I’ve also taken the graph below. It describes which antidepressant drugs have their apparent effect most boosted by the hiding of negative findings.

As we live in the age of ‘evidence based medicine’, doctors will used the available evidence to decide which drugs to prescribe.

Needless to say, distortions in the published results can affect individual patients owing to the effect on doctors decision-making.

Link to abstract of study.
Link to good write-up from the Wall Street Journal.