CHICAGO -- Habitual marijuana use increased among U.S. adults over the past decade, particularly among young minorities and baby boomers, government figures show. The prevalence of marijuana abuse or dependence climbed from 1.2 percent of adults in 1991-92 to 1.5 percent in 2001-02, or an estimated 3 million adults 18 and over. That represents an increase of 800,000 people, according to data from two nationally representative surveys that each queried more than 40,000 adults. Among 18- to 29-year-olds, the rate of abuse or dependence remained stable among whites but surged by about 220 percent among black men and women, to...