It cannot be assumed that an antidepressant has lost its effectiveness if a patient relapses while continuing on the medication, because the medication may never have been effective in the first place, according to study findings reported in the Journal of Clinical Psychiatry.

In the study, the majority of relapses occurred in patients who had never been true responders, Dr. Mark Zimmerman, director of outpatient psychiatry at Rhode Island Hospital, told Reuters Health.

Some patients with major depressive disorder, similar to other medical disorders, respond to placebo, Zimmerman explained. In clinical practice, everyone is given an active drug, so it’s not clear if a patient who responds has improve because of the drug or because of “nonspecific” effects, such as the placebo effect.

The placebo effect is a sort of “power of suggestion” response in which a patient begins to feel better because he thinks he has received treatment (and doesn’t know he has been given a placebo). These responses are usually short-term.

Similarly, relapses that occur during a continuation phase of treatment could be because of a true loss of response or they could be because an initial placebo response has worn off.

To investigate, Zimmerman collaborated with Dr. Tavi Thongy on a review of four studies involving 750 patients. These were continuation studies of new generation antidepressants.

Using two different methods of estimating relapse, the researchers found that the majority of relapses occurred because the patients were never true responsers to the drugs.

This suggests, Zimmerman told Reuters Health, “that a message can be conveyed to patients who have repeatedly improved on medication and then lost its benefit that perhaps they are more capable than they think in bringing their own resources to bear to improve their depression.”

SOURCE: Journal of Clinical Psychiatry, August 2007.