Some opponents of legalization worry that lax regulation of medical marijuana foretells even looser laws concerning recreational marijuana. In states that have legalized medical pot, current laws do not guarantee the safety or quality of cannabis products or standardize levels of THC. In Oakland, Calif., people can fill a marijuana prescription at Harborside Health Center, a massive dispensary with a strict quality-control system. Elsewhere in the state, however, people get their medical marijuana at mom-and-pop outfits or on the street. The next big round of ballot initiatives to legalize cannabis in states other than Washington and Colorado could happen as soon as three years from now, in the 2016 presidential election. Until then, researchers have plenty of marijuana health risks to weed through.