Two U.S. studies differ over effects of marijuana on drivers(This June 22 story has been refiled to correct study author’s name to “Aydelotte” instead of “Adedoyte” in third paragraph.) By Taylor Harris (Reuters) – Two U.S. studies on the effects of marijuana on drivers in states where it is allowed for recreational use came to different conclusions about whether it increases risks behind the wheel. A study by the American Journal of Public Health published on Thursday looked at motor vehicle fatalities and found no significant increase in Colorado and Washington State, where recreational marijuana use is legal, compared with eight states where it is not legal that have similar populations, vehicle ownership, and traffic laws. “Our study focused on deaths and actually found what we expected going into this,” Jason Aydelotte, lead author of the study said in a telephone interview.