The jury is still out on the effects of legalised cannabis in North America

Recent decades have seen a sea change in cannabis regulation in North America beginning with the legalisation of the drug for medicinal use in the 1990s in some US states and then referendums which legalised marijuana for recreational use in many states after 2014. But has cannabis legalisation been a good thing? Wayne Hall writes that despite growing support from the public and some state governments, there is simply not enough evidence yet to answer that question definitively.