Researchers at the University of Maryland's Center for Substance Abuse Research recently developed a set of warning signs to spot teenage use of marijuana, a popular recreational drug that often leads to experimentation with other illegal substances, officials said.

The study, released in late July, based its findings on a statewide survey conducted two years ago. The warning signs and recommendations were applauded by state educators and juvenile services officials, who said the findings validate their long-held ideas about ways to detect drug use among teenage students.

According to the four-page report, early marijuana users have the "highest risk of using other illegal drugs and developing serious drug- and alcohol-related problems." A system of nine "warning signs" was created to identify marijuana consumption among students, and one conclusion was that parents, educators and law enforcement authorities play an important role in identifying and preventing teens from using drugs.

"This is important because it's the first time we've been able to scientifically determine the signs and what can result from marijuana use," said Erin Artigiani, a spokeswoman for the center, also known as CESAR.

"We found that teenagers really do rely on their parents to shape their attitudes on drugs. We encourage parents to talk to their kids about drugs, to understand that drug use is a mistake and to be prepared for their responses."

The study was based on data collected in the 2002 Maryland Adolescent Survey, a biennial survey that questioned nearly 34,000 sixth-, eighth-, 10th- and 12th-graders about their experiences with drugs and alcohol. The CESAR study focused on marijuana because, according to the report, early use of that drug is "most strongly associated with other drug use and problems."

Warning signs include the use of cigarettes and alcohol before age 15, arrests for alcohol or drugs, 20 or more unexcused absences, and the attitude that smoking cigarettes and marijuana is safe.

"A lot of this is, yes, common sense, but there's the perpetual denial factor. Parents never want to believe that it's their kid," said Milt McKenna, the state Department of Education's specialist on safe and drug-free schools.

"What this report does is it tells us that these are no longer the things that we think and believe. Now we can say: 'Here are the facts. This comes from what your kids are telling us.'"

The report says that about 43 percent of high school seniors reported in 2002 that they used marijuana, and 20 percent had used the drug before they were 15. CESAR's Maryland Drug Early Warning System studied the relationship between the age a student first smoked marijuana and later drug and behavioral problems. By age 15, according to the report, 36 percent of the 12th-graders had used alcohol, 27 percent had smoked cigarettes, and 20 percent had smoked marijuana.

About 70 percent of the high school seniors had drunk alcohol at least once, and about one-fourth had used any of the 14 drugs they were asked about in the survey, including PCP, cocaine, crack cocaine and heroin.

"The aim of the warning signs is to help educators, parents and the state's juvenile system intervene sooner and, hopefully, avert those problems associated with drug use," Artigiani said.

The study recommended that the state's Department of Juvenile Services staff members work closely with schools and parents to encourage post-release intervention, such as special counseling sessions, for youths arrested and detained for alcohol- or drug-related offenses. It also suggested that state educators implement policies to ensure that students with warning signs receive help and that all students are taught the dangers of drug use.

"This report essentially tells us that students who hang out with their parents, students who receive direction from their parents, are at a lower risk of using drugs," McKenna said. "These are things we've always told parents, but now we have the data to back up our message. Without data, you're just another person with an opinion."

McKenna said the report and an accompanying brochure were made available to teachers across the state. He said a statewide Parent-Teacher Association meeting, to be held next month, will address the findings.