A national study, led by researchers at Queen's University, also found wealth and peer relationships have both positive and negative influences on youth health.

The report, released by the Public Health Agency of Canada in Ottawa, examines smoking, alcohol and drug use, physical activity and body image, eating patterns, emotional health and injuries in children ages 11 to 15. More than 9,500 students from grades 6 through10 participated in the survey in 2006.

The report, which compared teen data from 2002 and 2006, found:

-- Daily smoking among both boys and girls has declined significantly, from 15 percent to 4 percent of boys, and from 11 percent to 6 percent among girls.

-- In 2006, the proportion of 10th grade boys who reported ever trying marijuana dropped to 38 percent from 50 percent in 2002; girls remained about the same at about two-fifths.

-- Almost half of students are physically inactive. Fewer than half report daily consumption of fruits or vegetables, and only half report daily consumption of low-fat/skim milk.

A report summary is at: http://phac-aspc.gc.ca/dca-dea/yjc/index-eng.php.