E-cigarettes can act as a "gateway drug" and increase risk of substance abuse, a new study shows.

The study, conducted by researchers at the Columbia University Medical Center, shows that e-cigarettes aren't as safe as they are considered to be. In fact, teenagers using these cigarette alternatives are more likely to try other drugs such as marijuana and cocaine.

"While e-cigarettes do eliminate some of the health effects associated with combustible tobacco, they are pure nicotine-delivery devices," said Denise B. Kandel, from Columbia University Medical Center (CUMC), co-author of the study, according to a news release.

The study was presented to the Massachusetts Medical Society and is published in the journal New England Journal of Medicine. Howard Hughes Medical Institute and the National Institutes of Health and others have funded the research.

E-cigarettes are considered as way of lowering conventional cigarette use. However, these products are gaining popularity among adolescents and young adults faster than in older adults. The researchers say that any product containing nicotine can cause health problems.

"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," Dr. Eric Kandel, said in a news release.  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."

Denise Kandel and Eric Kandel have earlier shown that nicotine alters brain networks in mice models and makes them more susceptible to cocaine addiction, Time reported.

Further, Dr. Denise Kandel's research ion epidemiologic data also shows that nicotine primes human brains for cocaine addiction. People, who used cigarettes before switching drugs, were more likely to be dependent on cocaine, researchers found.