WASHINGTON (Reuters) - Teenagers who smoke are five times more likely to drink and 13 times more likely to use marijuana than those who are not smokers, according to a report issued on Tuesday.
The report by Columbia University's National Center on Addiction and Substance Abuse presented further evidence linking youth smoking to other substance abuse and spotlighted research on how nicotine affects the adolescent brain.
"Teenage smoking can signal the fire of alcohol and drug abuse or mental illness like depression and anxiety," Joseph Califano, who heads the center and is a former U.S. health secretary, said in a telephone interview.
The report analyzed surveys conducted by the U.S. Substance Abuse and Mental Health Services Administration and other data on youth smokers. Most smokers begin smoking before age 18.
Smokers ages 12 to 17 are more likely drink alcohol than nonsmokers -- 59 percent compared to 11 percent, the report found. Those who become regular smokers by age 12 are more than three times more likely to report binge drinking than those who never smoked -- 31 percent compared to 9 percent.
Binge drinking was defined as having five drinks or more in a row.
Asked whether smoking is causing these other behaviors or is just another risky behavior occurring alongside the others, Califano said, "There's no question that early teenage smoking is linked to these other things. Now whether it's causing it or not, I think the jury is probably still out on that."
Smokers ages 12 to 17 are more apt to meet the diagnostic definition for drug abuse or dependence in the previous year -- 26 percent compared to 2 percent, the researchers said.
The report noted that marijuana is the most widely used illicit drug among teenagers, with government data from 2005 showing 7 percent of those ages 12 to 17 used marijuana.
Of these, current cigarette smokers are 13 times more likely to use marijuana than those who do not smoke.
The younger a child is when he or she starts smoking, the greater the risk, the Columbia team said.
Children who start smoking by age 12 are more than three times more likely to binge on alcohol, nearly 15 times more likely to smoke marijuana and almost seven times more likely to use other drugs such as heroin and cocaine.
Teenagers who smoke also have a higher risk of depression and anxiety disorders, the study found.
The report cited scientific studies showing the nicotine in tobacco products can produce structural and chemical changes in the developing brain that make young people vulnerable to alcohol and other drug addiction and mental illness.
This includes effects on the brain chemicals dopamine and serotonin and changes to brain receptors associated with an increased desire for other addictive drugs.