A new report by the National Institute on Drug Abuse shows that the percentage of American high school students smoking marijuana is slowly increasing while the use of alcohol and almost every other drug is decreasing.
The use of marijuana is growing among teenagers due to the relaxation of restrictions on the drug — now it can be sold legally in 20 states and the District of Columbia. Health officials are worried about the use of marijuana by young students and say that adolescent brains, which are still in the development phase, are susceptible to subtle changes caused by marijuana, writes Anahad O'Connor of The New York Times.
According to study, more than 12% of eighth graders and 36% of senior students at public and private schools around the country said they had smoked marijuana in the past year. Also, around 60% of high school seniors said they did not see regular marijuana use as harmful, up from about 55% last year.
"The acceptance of medical marijuana in multiple states leads to the sense that if it's used for medicinal purposes, then it can't be harmful," said Dr. Nora D. Volkow, director of the National Institute on Drug Abuse. "This survey has shown very consistently that the greater the number of kids that perceive marijuana as risky, the less that smoke it."
Early next year, recreational marijuana use will become legal in Colorado and Washington. Heavy marijuana use may cause lasting detriment to the brain, and Dr. Volkow noted that marijuana might affect cognitive function in adolescents by disrupting the normal development of white matter through which cells in the brain communicate.
Not every substance is seeing increased use. According to the report, drinking was steadily declining with about 40% of high school seniors said they have used alcohol in the past month, down from 53% in 1997. The report also found that cocaine and heroin use decreased and was at historic lows in every grade.
Additionally, cigarette smoking also declined in recent years. For the first time since the survey began, the percentage of students who smoked a cigarette in the past month fell below 10%. About 8.5% of seniors smoke cigarettes on a daily basis compared with 6.5% who smoke marijuana daily, a slight increase from 2010.
According to analysis, the concentration of THC in marijuana has tripled since the early 1990s. Dr. Volkow said the rising use and increased potency could affect the likelihood of car accidents and could lower school performance.
"What is most worrisome is that we're seeing high levels of everyday use of marijuana among teenagers," Dr. Volkow said. "That is the type that's most likely to have negative effects on brain function and performance."
A new study by scientists at Northwestern University showed lasting brain alterations in people who smoked marijuana as adolescents. The scientists used brain imaging scans to compare young adults who had never smoked marijuana and those who used it daily for about three years as teenagers and found differences in the thalamus, globus pallidus and striatum.