Still, what do we know about the effects of, say, 15 to 20 years of antidepressant drug treatment that begins in adolescence or childhood? Not enough.

Image Credit... Courtney Wotherspoon

The reason has to do with the way drugs are tested and approved. To get F.D.A. approval, a drug has to beat a placebo in two randomized clinical trials that typically involve a few hundred subjects who are treated for relatively short periods, usually 4 to 12 weeks.

So drugs are approved based on short-term studies for what turns out to be long-term  often lifelong  use in the world of clinical practice. The longest maintenance study to date of one of the newer antidepressants, Effexor, lasted only two years and showed the drug to be superior to a placebo in preventing relapses of depression.

What do I say to a depressed patient who is doing well after five years on such a drug but can’t stop without a depressive relapse and who wants reassurance that the drug has no long-term adverse effects?

I usually say that we have no evidence that the drug poses a risk with long-term use; and since the risk of untreated depression is much greater than the hypothetical risk of the drug, it makes sense to stay on it.

This large gap in our clinical knowledge is compounded by the public’s growing and well-founded skepticism about research sponsored by drug makers. A study in the January 2008 issue of The New England Journal of Medicine, involving 74 clinical trials with 12 antidepressants, found that 97 percent of positive studies were published, versus 12 percent of negative studies.

Clearly, physicians and the public need much better data on the safety and efficacy of drugs after they hit the market, which at present consists mainly of anecdotes and case reports.