Pot is not just legal in many states; it’s also becoming big business. More than 30 states have made the product available for medical use, with ten letting adults buy or otherwise procure it for recreational purposes too. But the pot on the market today is more potent than it was 30 years ago, and the number of people with a self-described cannabis use disorder is rising. Academics and doctors think that legalization might have positive health effects overall. But they are worried that very potent, easily available pot might lead to some public health problems too. Marijuana prohibition has a tremendous fiscal cost and a far worse human cost. Researchers have convincingly argued that cannabis is far less dangerous than substances like alcohol. A solid majority of Americans support legalization. But a few decades ago, about one in ten cannabis users reported daily or near-daily use. Now, even more people are using it, and the share of monthly users who use it nearly every day is 40 percent by some estimates. That means that people who use cannabis are nearly three times as likely as drinkers to consume daily. And cannabis does have health effects, among them impairing cognitive function and inculcating dependence. About 9 percent of people who use marijuana develop that dependence, meaning they can have withdrawal symptoms, mood and sleep difficulties, cravings, and restlessness. For some small number of users, marijuana seriously impairs their quality of life. Lax regulatory standards and aggressive commercialization in some states might be compounding some of the public-health risks associated with cannabis, even as legalization reduces other public-health risks. The lack of federal involvement in legalization has meant that marijuana products are not being safety-tested like pharmaceuticals; measured and dosed like food products; subjected to agricultural-safety and pesticide standards like crops; or held to labeling standards like alcohol. This is not to say that prohibition is a more attractive policy, or that legalization has proven to be a public-health disaster. That’s not true either. “The big-picture view is that the vast majority of people who use cannabis are not going to be problematic users,” Jolene Forman, an attorney at the Drug Policy Alliance, told me. But there might be better ways for states to maximize the benefits of legalization while also minimizing the risks. The government could run marijuana stores, rather than leaving it to private businesses. States could bar budtenders – the people who sell you pot – from making medical claims. They could also cap the amount of THC in products, and bar producers from making edibles that are attractive to kids, like candies. Taxes on legal weed products could probably help curb consumption among the heaviest users. Such policies would help get rid of the financial and human costs of prohibition. They would also help make sure that cannabis use disorders do not become a bigger problem in the future.