Positive Sobriety Institute Dr. Fran Langdon: “If 100 people are exposed to marijuana once, nine will develop dependence on it”

FILE - In this Sept. 15, 2015 file photo, lead grower Dave Wilson cares for marijuana plants in the "Flower Room" at the Ataraxia medical marijuana cultivation center in Albion, Ill. Illinois officials posted new forms this week for doctors and patients in the state's medical marijuana program to reflect changes in the law, and announced Wednesday, Aug. 3, 2016, that July retail sales reached a new high at $2.9 million. (AP Photo/Seth Perlman, File)

TV travel guide Rick Steves recommends that the state of Illinois legalize marijuana. Positive Sobriety Institute addiction medicine specialist Fran Langdon argues why she thinks this would be a terrible idea, including stopping at a green light.