E-CIGARETTES designed to help people quit smoking may act as a "gateway" to harmful illicit drugs, researchers have said.
Like conventional cigarettes, the devices are said to raise the risk of addiction to banned substances such as cannabis and cocaine.
Scientists pointed out that while eliminating many of the toxic compounds found in tobacco, e-cigarettes delivered highly addictive "pure nicotine".
In mice, nicotine was found to alter brain biochemistry and prime the animals to develop a need for cocaine.
Analysis of human data suggested it had the same effect in people, with cocaine addiction rates highest among former cigarette smokers. "Our findings provided a biological basis for the sequence of drug use observed in people," US neuroscientist Professor Eric Kandel, who conducted the research with his wife, Dr Denise Kandel, said.
"One drug alters the brain's circuitry in a way that enhances the effects of a subsequent drug."
Writing in the New England Journal of Medicine, the married couple from Columbia University, New York, warned: "E-cigarettes have the same physiological effects on the brain and may pose the same risk of addiction to other drugs as regular cigarettes, especially in adolescence during a critical period of brain development.
"We don't yet know whether e-cigarettes will prove to be a gateway to the use of conventional cigarettes and illicit drugs, but that's certainly a possibility.
"Nicotine clearly acts as a gateway drug on the brain, and this effect is likely to occur whether the exposure comes from smoking cigarettes, passive tobacco smoke, or e-cigarettes."