According to the National Center on Addiction and Substance Abuse, teens who start smoking at a young age are three times more likely to binge drink, 13 times more likely to smoke marijuana and seven times more likely to use cocaine or heroin.

Animal experiments suggest that drugs - - including nicotine - - may alter the teenage brain.

Dr. Frances Leslie is a Professor of Pharmacology who says, "Our experiment would suggest that just one exposure to nicotine, the active component of tobacco, can produce a long-term change in the behavior of the animal that probably results from a change in the brain."

In fact, in studies on rats, nicotine exposure changes brain receptors, increasing the desire for other addictive drugs.

Dr. Leslie says, "It's hard at the moment to know how that translates into human behavior, but I think it's unquestionable that, um, there will be changes in behavior as a result of early smoking. And it's quite logical to believe that one of those changes in behavior might be increased drug use … of drugs like cocaine and amphetamine and heroin."