A new study discovered trials for new antidepressant medications may not be applicable to the population at large. Drug companies allegedly do not evaluate the efficacy of the medications on the general population but imply that the results of the trials work at large, even though they might work only for a narrow segment of depressed patients.
The finding, published in the Mayo Clinic Proceedings, shows recent trials are less generalizable than the prior studies, as researchers excluded most depressed patients from drug company-sponsored treatment studies. Patients with co-morbid psychiatric disorders have become frequently excluded together with patients with any co-morbid Axis I disorder, which were twice as likely to be excluded in recent studies.
Mark Zimmerman, M.D., a clinical researcher at Rhode Island Hospital, said the excluded patients are important in the trials as the majority of depressed patients have another psychiatric diagnosis. The patients under the inclusion or exclusion criteria for the clinical trials have been reduced over the past five years, most of excluded were with co-morbid psychiatric disorders and with any co-morbid Axis I disorder.
“More than a decade ago, our clinical research group raised concerns about the generalizability of the drug trials and suggested that the majority of patients seen in routine clinical practice would not qualify for a trial,” Zimmerman said. The previous study by Zimmerman also suggests, as the criteria for the clinical trials has narrowed down, the drug company-sponsored studies may be even less generalizable than they were previously.
Zimmerman analysed 170 placebo-controlled studies published within the past 20 years, including 56 published during the past five years. The analysis showed more recent studies were significantly done to exclude patients with co-morbid Axis I disorders and personality disorders, patients who met diagnostic criteria for major depression but did not score high enough on a rating scale, because the episode duration was too long or too short.
However, it is ethically sensible that severely ill patients with suicidal thoughts should be excluded from the trials because they may harm themselves or others, according to Zimmerman. But approximately half of the patients in clinical practice exclusion are covered by depressed patients, which Zimmerman noted as the most concerning issue. In addition, previous studies also found antidepressants do not work as well for less severely depressed patients.
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