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Study of drug therapy for compulsive buying yields a puzzle, Stanford researcher says

March 14, 2007

STANFORD, Calif. — Researchers at the Stanford University School of Medicine say they are puzzled by findings from their new study indicating that an antidepressant, which previously showed promise in treating a behavioral disorder known as compulsive buying, did not result in a sustained benefit for the patients who took it.

The medication is escitalopram, a commonly prescribed antidepressant sold under the brand name Lexapro. In the study, researchers found no difference in the relapse rate of people with compulsive-buying disorder when they continued to take escitalopram compared with those who had been switched to a placebo. Those results are perplexing to lead author Lorrin Koran, MD, professor of psychiatry and behavioral sciences emeritus, because he had done a similar study in 2003 that found compulsive-buying patients improved stably after taking another antidepressant medication, citalopram, in which escitalopram is the active ingredient.

"It was a shock that, when we did the trial again with the active ingredient, it didn't work exactly the same way. It should have," said Koran, who also led the 2003 study. The results of the latest double-blind, placebo-controlled trial will be published in the April issue of the Journal of Clinical Psychopharmacology.

Koran said the unexpected result from the new study may in part be due to the small number of participants in the double-blind phase of the trial, which involved just 17 subjects whose buying behavior had markedly improved in the initial stage of the trial when they were all taking escitalopram. Of the nine randomly assigned to take a placebo in the later part of the trial, six relapsed, while five of eight continuing on escitalopram relapsed.

But the study size is likely not the only factor influencing the outcome of the trial.

"I don't think we're dealing with one pure biological disorder," said Koran. "We're dealing with a behavior that has different biological roots in different people and therefore we may have had very different groups of people in the two studies."

In the 2003 study, 24 patients were all initially given citalopram for the open-label portion of the study, during which they all knew they were taking citalopram. Fifteen of those patients reported marked improvements in their buying behaviors. For the second portion of that trial, these 15 patients were randomly assigned to take either citalopram or a placebo without knowing which one they were taking. Of seven patients who continued taking the medication, all seven maintained their improvement, while five of the eight patients receiving a placebo relapsed.

People suffering from compulsive buying disorder are preoccupied with shopping for unneeded items and are frequently unable to resist purchasing them. The problem is not a simple lack of willpower, said Koran, who described it as being as real a disorder as other impulsive behaviors such as alcoholism and pathological gambling. Sufferers of the disorder commonly wind up with closets or rooms filled with unwanted purchases, amassing thousands of dollars of debt in the process and often damaging their relationships by lying to loved ones about their purchases.

A recent nationwide, random-sample telephone survey conducted by Koran and his colleagues indicated that compulsive buying appeared to affect nearly 6 percent of the U.S. population, with nearly equal proportions of men and women affected.

Koran said a larger double-blind, placebo-controlled clinical trial is needed to reach a conclusive result regarding the effectiveness of escitalopram in treating patients with compulsive buying disorder.

He suggested future clinical trials might be able to yield more information if they were combined with imaging studies of the patients' brains. He cited recent work by Brian Knutson, PhD, assistant professor of psychology and neuroscience, whose recent imaging studies suggest that scientists might be able to directly visualize brain activity related to compulsive purchases.

"We would look for a difference in the brain activation patterns of those who respond to the drug vs. those who don't," said Koran.

The inconclusive nature of the results from the latest trial of escitalopram should not discourage anyone suffering from compulsive buying from seeking treatment, since several types of treatment seem to be helpful, Koran emphasized.

Stanford University Medical Center