Electronic cigarettes, known by a variety of names including vapour pens, are battery-powered devices that heat nicotine and flavourings to deliver an aerosol inhaled by the user.
While they are promoted as a way to quit traditional cigarettes, they also are promoted as a way to get nicotine in environments where traditional cigarettes are prohibited.
Researchers at the University of California in San Francisco (UCSF) reviewed 38 studies assessing the association between e-cigarette use and cigarette cessation among adult smokers.
The studies included smokers who both were and were not interested in quitting, and included people as young as 15 years old.
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The studies included in the analysis controlled for many variables, including demographics, past attempts to quit, and level of nicotine dependence.
"The irony is that quitting smoking is one of the main reasons both adults and kids use e-cigarettes, but the overall effect is less, not more, quitting," said Stanton A Glantz from UCSF.
The findings were published in the journal The Lancet Respiratory Medicine.