Antidepressants only benefit some

A new study published in PLoS Medicine suggests that antidepressants only benefit some, very severely depressed patients.

“New generation” antidepressants, such as fluoxetine (Prozac) are widely prescribed for the treatment of clinical depression. However some studies have suggested that these drugs do not help the majority of depressed people get better by very much. Irving Kirsch, from the University of Hull, and his colleagues, studied this question in closer detail, looking at whether a patient's response to antidepressant therapy depends on how badly depressed they are to start out with.

Kirsch and colleagues used a technique called “meta-analysis”, where they put together data on clinical benefit from all the trials submitted to the US Food and Drug Administration for four drugs: fluoxetine (Prozac), venlafaxine (Effexor), nefazodone (Serzone), and paroxetine (Seroxat / Paxil). (The researchers also wanted to include sertraline and citalopram, but couldn't find all the relevant data for those two drugs). By including data from unpublished as well as published trials, the researchers set out to avoid bias that might come from non-publication of disappointing findings.

When the data from all of these trials had been put together, the improvement in depression amongst patients receiving the trial drug, as compared to those receiving placebo (dummy tablets), was not clinically significant in mildly depressed patients or even in most patients who suffer from very severe depression. The benefit only seemed to be clinically meaningful for a small group of patients who were the most extremely depressed to start out with. This improvement seemed to come about because these patients did not respond as well as less depressed patients to placebo, rather than responding better to the drug.

Irving Kirsch, summarising the paper, says: “Although patients get better when they take antidepressants, they also get better when they take a placebo, and the difference in improvement is not very great. This means that depressed people can improve without chemical treatments.”

Given these results, the researchers conclude that there is little reason to prescribe new-generation antidepressant medications to any but the most severely depressed patients unless alternative treatments have been ineffective.