New research links laws legalizing recreational marijuana with an increase in traffic deaths. But the findings in two studies published Monday don’t answer how these laws might influence driving habits. Previous research has had mixed results and the new studies can’t prove that the increases they found were caused by marijuana use. One of the studies looked at four states that allow recreational pot sales. It says if every state legalized recreational marijuana sales, an extra 6,800 people would die each year in traffic accidents. Recreational pot is legal in 11 states. The studies appear in JAMA Internal Medicine.