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Imagine conducting a clinical trial and then being unable to publish the results. For cannabis researchers in the United States, that is often the sad reality. Although the US Food and Drug Administration (FDA) has approved several single-agent drug preparations that comprise purified or synthetic cannabinoids, medical-cannabis products are prohibited by federal law. Under this regime, it is impossible to get approval for a phase II trial or beyond, and there are tight limitations on publishing cannabis-related clinical data. About one-quarter of the US population live in parts of the country where cannabis can be purchased legally as easily as beer, yet research on what they are consuming is highly restricted. Adding to the frustration is a growing body of evidence that points to potential medical benefits of cannabis.