People with mental health conditions were found more likely to use e-cigarettes, according to a recent study.

Researchers at the University of California, San Diego School of Medicine found that people living with depression, anxiety, or other mental health conditions are twice as likely to have tried e-cigarettes and three-times as likely to be current users of the devices, as people without mental disorders.

They are also more susceptible to trying e-cigarettes in the future in the belief that doing so will help them quit, the scientists said. The FDA has not approved e-cigarettes as a smoking cessation aid.

"The faces of smokers in America in the 1960s were the 'Mad Men' in business suits," Sharon Cummins, lead author of the study and an assistant professor in the Department of Family and Preventive Medicine, said in a statement. "They were fashionable and had disposable income. Those with a smoking habit today are poorer, have less education, and, as this study shows, have higher rates of mental health conditions."

People with psychiatric disorders consume approximately 30 to 50 percent of all cigarettes sold annually in the United States.

The study is based on a survey of more than 10,000 Americans' smoking history, efforts to quit and their use and perceptions about e-cigarettes. People were also asked whether they had ever been diagnosed with an anxiety disorder, depression or other mental health condition.

In the survey, nearly 28 percent of current smokers had self-reported mental health conditions, compared with 13.4 percent of non-smokers. Nearly 15 percent of individuals with mental health conditions had tried e-cigarettes, and 3.1 percent were currently using them, compared with 6.6 percent and 1.1 percent without mental health conditions, respectively.

Researchers also found that 60.5 percent of smokers with mental health conditions indicated that they were somewhat more likely or very likely to try e-cigarettes in the future, compared with 45.3 percent of smokers without mental health conditions.

"People with mental health conditions have largely been forgotten in the war on smoking," Cummins said. "But because they are high consumers of cigarettes, they have the most to gain or lose from the e-cigarette phenomenon. Which way it goes will depend on what product regulations are put into effect and whether e-cigarettes ultimately prove to be useful in helping smokers quit."

Researchers said the study shows that smokers, regardless of their mental health condition, are the primary consumers of the nicotine delivery technology. People with mental health disorders also appear to be using e-cigarettes for the same reasons as other smokers -- to reduce potential harm to their health and to help them break the habit.

The findings were recently published in the online issue of Tobacco Control.