ATLANTA - Cocaine, marijuana and cigarette use among high school students increased during the 1990s, according to a government survey that also says fewer teens are having sex and those who do are more likely to use condoms.
The Centers for Disease Control and Prevention report, issued Thursday, showed improvement in some risky behavior - more students wear seat belts and fewer are carrying weapons or contemplating suicide.
''There is reason to feel optimistic about many of the trends in risk behaviors among our young people,'' CDC Director Jeffrey Koplan said. ''However, we have much left to do. Too many of our children are still engaging in activities that put them at risk for health problems now and into adulthood.''
The increases in smoking and drug use came despite years of goverment-funded media campaigns urging teen-agers to stay clean and sober. The drop in sexual activity came during a period in which health officials urged everyone to practice safe sex to avoid AIDS.
Every two years since 1991, the CDC has distributed questionnaires to a scientific sampling of students to measure behavior that endangers their health. This year's survey involved 15,349 students in grades nine through 12.
In 1991, 14.7 percent of the students surveyed said they use marijuana. That number steadily increased to 26.7 percent in 1999. Students reporting they have tried marijuana at least once increased from 31.3 percent in 1991 to 47.2 percent in 1999.
In 1991, 1.7 percent of the students surveyed said they used cocaine at least once in the prior month. By 1999 that number rose to 4 percent. Those who had at least tried cocaine increased from 5.9 percent in 1991 to 9.5 percent in 1999.
Howard Simon, spokesman for the New York-based Partnership for a Drug-Free America, said the past decade brought increased drug use among teen-agers, but he expects new figures in the past year to show improvement.
''We have reversed those trends and started to edge back down just in the last year,'' he said. ''But don't get me wrong, we're still at the top of a very dangerous and disturbing mountain.''
Andy Meisner, a spokesman for the Community Anti-Drug Coalition of America, said the marijuana boom started to trail off in 1997. But he added that alcohol and tobacco use are also major concerns.
While alcohol use has remained steady since 1991, the student survey indicates more teens are smoking.
In 1991, 27.5 percent of the students surveyed reported they had smoked at least once in the previous month. That increased to a high of 36.4 percent in 1997 then dropped to 34.8 percent in 1999. However, frequent cigarette use gradually climbed from 12.7 percent in 1991 to 16.8 percent in 1999.
''I think 35 percent is alarmingly high, especially with all that we know about the devastating affects of tobacco use,'' said Cassandra Welch, spokeswoman for the American Lung Association.
She said the indication that tobacco use may have peaked in 1997 is a good sign that efforts to discourage smoking may be working.
In other trends, fewer high school students said they have had sex, a trend that gradually decreased from 54.1 percent in 1991 to 49.9 percent in 1999. The number of students who said they were currently sexually active remained fairly consistent since 1991 at around 36 percent. However, more reported using a condom - 58 percent in 1999 compared to 46.2 percent in 1991.
Fewer students also reported having had four or more sex partners and 90.6 percent reported having been taught about AIDS in school in 1999, an increase over the 83.3 percent in 1991.
In 1991, 29 percent of the high school students reported contemplating suicide, a trend that gradually declined to 19.3 percent in 1999.