The effects of using of e-cigarettes is stronger in adolescents than adults, experts claim.
Professor Eric Kandel, whose research suggests E-cigarettes could lead to harder drug use, said: "The effects we saw in adult mice are probably even stronger in adolescent animals.
"One drug alters the brain's circuitry in a way that enhances the effects of a subsequent drug. Therefore, we should do all we can to protect young people from the harmful effects of nicotine and the risks of progressing to illicit drugs."
More than a million people in the UK are believed to get their nicotine fix from e-cigarettes but opinion is divided about the safety of them.
The first E-cigarette dates back to 1963 in Pennsylvania when a 40-a-day smoker filed for a patent "smokeless non-tobacco cigarette".