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Editorial |

The Potential Value of a Negative Finding An Illustrative Example

Kenneth Silverman, PhD; Anthony DeFulio, PhD; Jeannie-Marie Leoutsakos, PhD
JAMA Psychiatry. 2013;70(6):571-572. doi:10.1001/jamapsychiatry.2013.1116.
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Clinical trials with positive findings are more likely to be submitted and published than those with negative findings,1 but negative findings can provide invaluable information, particularly when based on sound methodology. The study by Somoza and colleagues2 in this issue provides a powerful illustration of the potential value of a negative finding.

Somoza et al2 report the results of a clinical trial that evaluated the safety and efficacy of vigabatrin for treating cocaine dependence. The quality and rigor of this study2 is outstanding. In addition to using the standard features of clinical trials, several features deserve recognition, including the use of a baseline period prior to randomization during which participants had to show evidence of cocaine use, thereby ensuring that participants were current cocaine users; the provision of vouchers contingent on the submission of valid urine samples for both groups, to promote retention and consistent submission of urine samples; and the use of outcome measures that were based partly on urinalysis results and thus provided objective evidence of abstinence or use. An important feature of this study2 is that participants in both groups were retained at high and virtually identical rates. Specifically, 77% and 75% of participants in the vigabatrin and placebo groups, respectively, completed the treatment phase of the study, and participants in the 2 groups provided 74% and 75% of the urine samples, respectively. The high retention and collection rates were probably a function of the voucher reinforcement used in the study, and allow for a rigorous and valid assessment of the efficacy of vigabatrin in treating cocaine dependence. In this study,2 vigabatrin did not have a significant effect on the primary outcome measure of cocaine use.

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