While most people who smoke marijuana do not go on to use other drugs, long-term studies of high school students show that few young people use other illegal drugs without first trying marijuana. For example, the risk of using cocaine is much greater for those who have tried marijuana than for those who have never tried it. Using marijuana puts children and teens in contact with people who use and sell other drugs. So, a person who uses marijuana is more likely to be exposed to and urged to try other drugs. The effects of marijuana on the brain of adolescents—still a work in progress—may also affect their likelihood of using other drugs as they get older. Animal studies suggest this to be true, but it is not yet demonstrated in people.