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August 27, 2015
Depression Medication Studies Becoming More Selective,
Less Generalizable Providence, RI—Results of clinical studies on the efficacy of antidepressants might be less generalizable than in the past, according to a new study finding that inclusion/exclusion criteria have narrowed considerably over the last 5 years. The study was published recently in Mayo Clinic Proceedings. For the study, Mark Zimmerman, MD, a clinical researcher at Rhode Island Hospital, and colleagues analyzed the criteria used in antidepressant efficacy studies (AETs), finding that most patients seeking admission to the trials are excluded. “The inclusion/exclusion criteria for AETs have narrowed over the past five years, thereby suggesting that AETs may be even less generalizable than they were previously,” explained Zimmerman. “More than a decade ago, our clinical research group raised concerns about the generalizability of AETs and suggested that the majority of patients seen in routine clinical practice would not qualify for an AET,” he added in a press release from Lifespan health system. “These results were replicated multiple times. We therefore wondered if drug companies changed how they recruited patients into studies. In fact, they have, but in an unexpected way. The more recent AETs are even less generalizable than the prior studies, which themselves excluded most depressed patients from drug company-sponsored treatment studies.” For the study, researchers reviewed 170 placebo-controlled AETs published during the past 20 years, 56 of which were published during the past 5 years. They found that recent studies were significantly more likely to exclude patients for the following reasons: • They had comorbid Axis I disorders and personality disorders; • Their depressive episode duration was too long or too short; and • They met diagnostic criteria for major depression but did not score high enough on a rating scale. “For severely ill patients, such as those who express suicidal thoughts, it makes ethical sense to exclude them from a study where they may receive placebos,” Zimmerman suggested. “However, excluding patients with co-morbid psychiatric disorders has become more frequent, and patients with any comorbid Axis I disorder are twice as likely to be excluded in recent studies. This is important because the majority of depressed patients have another psychiatric diagnosis.” Even more concerning, he said, is the exclusion of depressed patients who score too low on rating scales, pointing out that would exclude about half of the patients seen in clinical practice. Zimmerman also posited that results could be skewed because “studies have shown that antidepressants do not work as well for less severely depressed patients. Thus, drug companies seem to be stacking the deck to demonstrate that their products work, even though they might work only for a narrow segment of depressed patients.”
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