A landmark study by the Mental Health Council of Australia, "Where There's Smoke," shows that even casual marijuana use increases the risk of psychosis and worsens almost any mental illness, especially depression and bipolar disorder. As reported by Australian television over the weekend, cannabis use is associated with other adverse outcomes, including poor employment and education outcomes. The study adds new importance to a recent Minneapolis Star-Tribune article on a U.S. government survey that found illegal drug use, notably marijuana, by Americans in their 50s rose a stunning 63 percent from 2002-05. (Over the same period, it fell by 15...