Moderate cannabis use appears to cause no long-term damage to the lungs, according to a new study by the University of California at San Francisco and the University of Alabama at Birmingham, released Jan. 10 in the Journal of the American Medical Association. Results of the 20-year study, funded by the National Institute on Drug Abuse, indicate that cannabis doesn't do the kind of damage tobacco does.
The study randomly enrolled 5,115 men and women aged 18 through 30 in four cities: Birmingham, Chicago, Oakland and Minneapolis. Roughly equal numbers of Blacks and whites took part, although no other ethnic groups. About 37% reported at least occasional cannabis use, and most users also reported having smoked cigarettes; 17% said they'd smoked cigarettes but not cannabis. Those figures are in line with national estimates. On average, cigarette users smoked about nine cigarettes daily, while average cannabis use was only a joint or two a few times a month—also a figure typical for US cannabis users, study co-author Stefan Kertesz said.
The results are less clear for heavy users—those who smoke two or more joints daily for several years. The data did suggest that using cannabis that often might cause a decline in lung function—but there weren't enough heavy users among the 5,000 young adults in the study to draw firm conclusions. Still, the authors recommended "caution and moderation when marijuana use is considered." (USA Today, San Francisco Chronicle, Jan. 10)
Graphic by Americans for Safe Access