The only marijuana available for research in the U.S. is locked down by federal regulators who are more focused on studies to keep people off the drug than helping researchers learn how it might be beneficial.

Marijuana is a trend that "will peak like tobacco, then people will see their error," said Nora Volkow, director of the National Institute on Drug Abuse (NIDA), which serves as the gatekeeper for U.S. marijuana research through its oversight of a pot farm that grows the only plants that can be used in clinical trials.

Marijuana advocates say NIDA's control over research has restricted their ability to test the drug against ailments such as pain, cancer-related nausea and epilepsy.