Nicotine is extreemely harmful to the developing adolescent brain, USC study finds.

Even if it is inhaled as smoke-free aerosol, vaping a higher concentration of nicotine may increase how often teenagers use electronic cigarettes or smoke traditional cigarettes, according to a Keck School of Medicine of USC study.

This is the first study to evaluate the association of e-cigarette nicotine concentration with future smoking and vaping behavior in youth, researchers said.

“We know that smoking is one of the most dangerous things that you can do for your health, especially if you begin during adolescence,” said Adam Leventhal, corresponding author of the study and director of the USC Health, Emotion and Addiction Laboratory at the Keck School of Medicine. “Because nicotine has mood-elevating and addictive effects, teens who use e-cigarettes with stronger nicotine concentrations may be less willing to stop vaping and be more inclined to use other nicotine products, like conventional cigarettes.”

The study, published in JAMA Pediatrics journal on October 23, found that 43 percent of high school students who used high-nicotine e-cigarettes (18 milligrams per milliliter or more) at the start of the study were “frequent smokers” at the follow-up six months later, meaning they smoked traditional cigarettes at least three times in the past month. Only 10 percent of those who used low-strength e-cigarettes (1-5mg/mL of nicotine) and 6 percent of those who used nicotine-free e-cigarettes were frequent smokers at the follow-up.

In comparison to teens who vaped nicotine-free e-cigarettes, those who vaped high-nicotine e-cigarettes smoked 14 times as many cigarettes per day, which translates to multiple cigarettes per day on average.

“We know that teens who vape e-cigarettes are much more likely to become conventional cigarette smokers,” Leventhal said. “Our study suggests that the nicotine in e-cigarettes may be a key reason why teens who vape progress to more frequent smoking.”

“Nicotine is highly addictive and may harm the developing teenage brain by increasing the risk of attention problems and depression,” Leventhal said.

“While previous research reported that most adolescents were using nicotine-free e-cigarettes, results from our survey and other soon-to-be published studies show that many more teens are vaping e-cigarettes with nicotine than we originally thought,” said Leventhal, associate professor of preventive medicine and psychology at the Keck School of Medicine. “Our study indicates that teens who vape more nicotine may be at greater risk for critical adverse health effects like becoming a regular smoker of conventional cigarettes and becoming a regular user of e-cigarettes.”

The study included surveyed answers from 181 students at 10 high schools in Los Angeles. Initial data was collected in the spring of 10th grade. Follow-up survey data was collected six months later in the fall of 11th grade. The use of e-cigarette liquid with high concentrations of nicotine was associated with increased and more frequent use of both e-cigarettes and regular cigarettes.

E-cigarette liquids are sold in nicotine concentrations ranging from 0 mg/mL to more than 25 mg/mL, the study reported. In the student survey, nicotine concentration was categorized as none, low (1-5 mg/mL), medium (6-17mg/mL) and high (18 or more mg/mL).

For each level up in nicotine strength, participants were two times more at risk of smoking three days or more in the month preceding the follow-up.

USC is devoted to promoting health across the life span. Previous e-cigarette research led by Keck School of Medicine researchers found that teens who are unlikely to have smoked cigarettes if e-cigarettes didn’t exist are now vaping and that teens who vape are at increased risk of becoming conventional cigarette smokers. These studies raise concern whether e-cigarettes m