The high-potency marijuana now widely available in cities and some small towns is causing an increasing number of teenagers -- and some preteens -- to land in drug treatment centers or emergency rooms, recent government statistics suggest.
The numbers are not conclusive, experts say, but have renewed scientific interest in and debate about the risks of marijuana use.
"The stereotypes of marijuana smoking are way out of date," said Michael Dennis, a research psychologist in Bloomington, Ill. "The kids we see are not only smoking stronger stuff at a younger age but their pattern of use might be three to six blunts -- the equivalent of three or four joints each -- just for themselves, in a day. That's got nothing to do with what Mom or Dad did in high school. It might as well be a different drug."
Though overall marijuana use in minors has declined slightly since the mid-1990s, recently released statistics from hospitals and treatment centers suggest that the drug is causing many young users serious problems. Late last year, federal health officials reported that the number of marijuana-related emergency room visits for children age 12 to 17 had more than tripled since 1994, to 7,535 in 2001, the latest year for which figures were available. The most common reason for the visit was an "unexpected reaction" to the drug. "Overdose" was cited in 10% of these cases, "chronic effects" in 6% and "accident or injury" in 4%.
The latest U.S. Health and Human Services Department data show that marijuana or hashish use is, by far, the most common reason why children age 12 to 17 were placed in licensed public or private treatment centers, accounting for more than 60% of reported cases in 2001.
In an analysis published last week, researchers at Columbia University's National Center on Addiction and Substance Abuse calculated that the treatment rate for cannabis dependence or habitual use in youngsters had jumped 142% in the last decade.
It is too early to tell whether these statistics truly represent a surge in habitual use, experts said. Admission figures could be skewed by changes in the way some states collect data and report it to the federal government. Forced drug treatment is also a way many teens avoid juvenile detention after a drug arrest.
Most children who smoke marijuana are occasional users, experts said. And there is little evidence that a heavy marijuana user who quits the habit will experience the kind of physical withdrawal symptoms reported by heroin or cocaine users.
Because marijuana seized by federal authorities today is about twice as potent as it was in the 1980s, health officials are taking the drug more seriously.
Although some scientists doubt that marijuana induces real physical dependence, many top drug researchers have concluded otherwise. "There is no question marijuana can be addictive; that argument is over," said Dr. Nora Volkow, director of the National Institute on Drug Abuse. "The most important thing right now is to understand the vulnerability of young, developing brains to these increased concentrations of cannabis."
More than 50 government-funded studies of cannabis are underway, and Volkow has pledged agency funds to investigate areas related to regular marijuana use. These include:
* Effect of cannabis on the young brain. Doctors have little understanding of how regular marijuana use alters the biological development of the brain. Clinicians who treat heavy users say that the earlier a person starts taking the drug, the more quickly a habit takes hold. "The risk of becoming addicted is far higher for a child in junior high than it is for someone who tries it in high school," said Dennis, a researcher at Chestnut Health Systems, a large behavioral care provider in Bloomington. Regular use can also exacerbate symptoms of attention deficit hyperactivity disorder and trigger latent mental disorders, some doctors believe.
* Medications to help break the habit. In recent years, doctors have had some success treating narcotic addiction with drugs such as buprenorphine, which is used for heroin dependence. They have done very little testing of drugs to ease marijuana craving.
* Genetic susceptibility. In a recent study of 198 young people, doctors in New Zealand found that those who reported enjoying their first-time use of marijuana were more likely to develop a habit later on. The researchers said their findings suggested that some people might be genetically vulnerable to addiction. Volkow is encouraging researchers to isolate genes that may contribute to the vulnerability.