If you want your kids to stay away from drugs, then you might want to keep teenagers off alcohol because a new study says that long term drug abuse is likely to occur due to alcohol, not marijuana, use.

The present study included data on more than 14,500 high-school students from 120 schools across U.S. The data was obtained from Monitoring the Future study.

Researchers analyzed the data to find out what substances were being tried by students. They checked for use of marijuana, cocaine, heroin, LSD, amphetamines, tranquilizers and other narcotics. Alcohol was the first substance to be tried by students, the results showed.

“By recognizing the important predictive role of alcohol and delaying initiation of alcohol use, school officials and public health leaders can positively impact the progression of substance use. I am confident in our findings and the clear implications they have for school-based prevention programs. By delaying and/or preventing the use of alcohol, these programs can indirectly reduce the rate of use of other substances," Adam Barry, an assistant professor and researcher in the College of Health and Human Performance at the University of Florida.

“These findings add further credence to the literature identifying alcohol as the gateway drug to other substance use,” Barry said.

Estimates from major surveys in U.S say that by age 17 most teenagers, between 59 percent and 71 percent, had consumed alcohol, 31 percent to 44 percent had tried cannabis, and 4 percent to 6 percent had tried cocaine, in a study published in the Archives of General Psychiatry.

Researchers say that parents should prevent teenagers from drinking. Alcohol is commonly available and isn't considered as taboo as other substances but many studies have shown that alcohol abuse in early years can make teenagers more likely to abuse other drugs.

The study doesn't clearly define how drug abuse actually starts but it does provide some idea about a good intervention program to keep children from becoming long-term drug abusers.

“Parents should know that a strict, zero-tolerance policy at home is best. Increasing alcohol-specific rules and decreasing availability will help prevent an adolescent’s alcohol use. The longer that alcohol initiation is delayed, the more likely that other drug or substance use will be delayed or prevented as well," he said.

The study was published in the Journal of School Health.