The study found that cigarette smokers who used both e-cigarettes and traditional combustible cigarettes smoked more combustible cigarettes daily on average.

A new study by UMass Medical School researchers may up-end a common belief about the benefit of e-cigarettes for helping smokers kick the habit.

The notion that e-cigarettes can be a helpful transition for cigarette smokers trying to quit “is a prevailing belief for many people who started smoking e-cigarettes,” said lead author Nancy Anoruo, MD, MPH, a third-year resident in medicine. The study found that cigarette smokers who used both e-cigarettes and traditional combustible cigarettes smoked more combustible cigarettes daily on average and had less success abstaining temporarily or quitting completely than traditional smokers who only used combustible cigarettes. The research included 405 smokers who participated through several hospitals in Massachusetts. The smokers expressed low or no intention of quitting smoking.

Participants who reported having ever smoked an e-cigarette were characterized as dual smokers. Traditional smokers only reported use of combustible cigarettes. At baseline, dual smokers smoked an average 16 combustible cigarettes per day, compared with 14 cigarettes per day for traditional smokers.

All smokers were encouraged to consider a brief period of abstinence from combustible cigarettes during the three weeks after baseline.

Among the significant findings, 6.3 percent of dual smokers were successfully able to quit smoking completely at three weeks, versus 13 percent of traditional smokers. At six months, dual smokers smoked more cigarettes daily than traditional smokers, with an average daily number of 12 versus 9.4 for traditional smokers.

E-cigarettes have less of the toxic chemicals that combustible cigarettes have, Dr. Anoruo said. But she said, “If they make you smoke more cigarettes, it cancels out any benefit from reduced toxic chemicals from the e-cigarettes.”

The study was accepted for presentation at the annual conference of the American Thoracic Society, which was moved online due to the COVID-19 pandemic. Co-authors include the following members of the Department of Population Health & Quantitative Health Sciences: Jinying Chen, PhD, assistant professor; Julie Flahive, MS, biostatistician; Thomas Houston, MD, adjunct professor; and Rajani Sadasivam, PhD, associate professor.