Among health experts, the jury is still out on THC, CBD and the use of marijuana in general, as those in medical and research fields weigh the benefits and risks. "This is the big challenge with cannabis: How do we facilitate the beneficial medical applications, allow for what society has determined is acceptable recreational use and also guard against the very real harms?" Gregory Tung, Ph.D., an associate professor at the Colorado School of Public Health, tells USA TODAY. "This is difficult and will likely require a mix of policy, rules, regulations and education."