The issue focused on individual uses of medical marijuana. The study found that while 14 percent of California residents use medical marijuana, only 5 percent are currently registered with the state.

As medical marijuana research continues to expand in California, researchers say they're learning more about how medical marijuana works and what side effects it can cause. They also want to better understand how medical marijuana affects different types of cancer patients.

In particular, researchers want to know if medical marijuana users get worse when using it for medical reasons or