Mohamed Naguib at M.D. Anderson Cancer Center has a paper in Anesthesia and Analgesia about a synthetic cannabinoid that has some of the benefits (relief of neuropathic pain) without the other psychoactive properties we associate with marijuana.
It's not clear that any recent changes in the body of law or law enforcement allowed this instance medical progress, it's very difficult to argue that it was not slowed by our current illegal drug classification system. The absurdity that marijuana is a Schedule I substance while methamphetamine and cocaine are Schedule II cannot be overstated. The irrationality of the classification system, as well as selective enforcement and public perception that stems from inconsistent policy, must have chilling effects on legitimate medical research, including for basic pain relief like Dr. Naguib's research. Even if physicians, medicinal chemists and the actual medical research labor force are willing to take these risks, their institutions and funding sources are understandably more nervous when they're dealing with any chemical entity even in the "neighborhood" of ones that are of particular interest as contraband.
The question is, how do we assess the damage done, both in economics as well as lost utility, by neighborhood chilling effects? Regardless whether a moral argument is made about the laws surrounding psychoactive substances, it seems obvious that in this case Naguib's research would be easier to do in the absence of substances in the same chemical family being illegal. Economists must have some way of modeling whether there would have been an overall difference to the economy or the growth of an industry in the absence of criminalization of related goods.