Source: Fox News Pubdate: Fri, 17 Jul 1998


NEW YORK, Jul 17 -- Smoking marijuana may cause gene mutations that can trigger cancer, researchers report.

"Smoking marijuana is every bit as risky as smoking cigarettes,'' concludes study lead author Dr. Marinel Ammenheuser of the University of Texas Medical Branch at Galveston. The findings appear in the current issue of the journal Mutation Research.

And the effects of marijuana may be particularly severe in the unborn child, with a potential for causing birth defects or childhood cancer, according to the report.

Recent surveys have revealed that a growing percentage of teenagers believe marijuana is a relatively harmless substance, especially when compared with tobacco or alcohol. In a statement, Ammenheuser noted that many of the young women involved in her study "told us very proudly that they didn't smoke tobacco, that they only smoked marijuana.''

The Texas researchers conducted DNA tests on blood samples obtained from 17 of these young women (all clients of a local prenatal clinic), and compared the results to those of 17 healthy non-smoking women who did not use marijuana.

They focused their DNA research on mutations within the 'hprt' gene. They explained that mutations in this gene act as a kind of indicator of "DNA damage potentially occurring in other areas of the genome.''

The results? The authors discovered that regular marijuana users had three times as many hprt mutations as non-users. Furthermore, the users' mutation rates were actually slightly higher than those of light tobacco users (5 to 8 cigarettes per day), as assessed in a previous study. This finding did not surprise the investigators, since they say "tobacco smoke and marijuana smoke contain many of the same carcinogens and mutagens.''

DNA mutations can be a real cause for concern, the Texas team conclude, since they "have been identified as early events in the development of cancer.'' Previous research has already uncovered cases of tongue, lung, and head and neck cancers in long-time marijuana users who did not smoke tobacco. The researchers say another study reported "a 10-fold risk of leukemia in the offspring of mothers who smoked marijuana during pregnancy.''

Many experts believe the cancer risks of long-term marijuana use may become more apparent in coming decades. This is because many current, long-term "pot'' smokers began their habits in the 1960s and 1970s, and the associated genetic damage linked to their ongoing carcinogen intake could take a long time to reach "threshold'' levels where it triggers cancer.

Ammenheuser says she is concerned about today's first-time marijuana users as well. "Young people may be convinced that there's some risk, way in the distant future, from smoking tobacco,'' she says, "but they're not so cautious about marijuana. Hopefully, with this new information, teenagers who smoke marijuana will stop. Or better yet, they'll never start.''

SOURCE: Mutation Research 1998;403:55-64.