Many professional athletes are no strangers to accusations of using performance-enhancing drugs. Barry Bonds, Floyd Landis and Jason Giambi are just some of the big names that have recently faced accusations of steroid use.

A little less known is the use of doping substances on the junior high school circuit.

While studies have already shown that 3 to 5 percent of adolescents may be involved in doping, a new study in Wednesday's online edition of the British Journal of Sports Medicine found more than 1 percent of preadolescents are using performance-enhancing drugs.

The study followed 2,199 French sixth graders for four years, using self-reported questionnaires every six months.

The questionnaires asked about banned doping agents included on the World Anti-Doping Agency's international prohibited list of drugs, as well as alcohol, tobacco and cannabis. The students were also questioned about their involvement in sports, and their levels of self-esteem and anxiety.

Click here to see the WADA's 2007 Prohibited List.

In the beginning of the study, researchers found 1.2 percent of the preteens had taken a doping agent at least once in the previous six months. That number jumped to 3 percent four years later.

And while 15 percent of the 11-year-olds polled were using doping agents once a week, that figure more than doubles to 38 percent amongst the 15-year-olds.

The most popular doping agents among the young athletes were corticosteroids, salbutamol, anabolic agents, and other stimulants.

Overall, almost half of the children who used a banned substance reported they had won at least one sporting event as a result.

Although 4 percent of the users reported health problems, such as becoming violent and loss of consciousness, the authors noted it was difficult to quantify these findings because they "may be impressions rather than facts."

Not surprisingly, the researchers confirmed earlier studies that boys were more likely to take the drugs than girls. The authors of the study encourage coaches, parents and teachers that there are warning signs.

The amount of time spent training, self-esteem, and a young athlete's intention to try performance-enhancing drugs are all red flags to watch out for.

"Young athletes who are tempted to use doing agents are more likely to be boys, invest much more time in training, are ready users of psychoactive substances, and, importantly, they appear to be in some distress," the authors concluded in the study. "Furthermore at least six months previously, they have said that they had been tempted to try a prohibited drug. Adults responsible for young people should be alerted by these signs."