A new study found that people with mental health conditions are three times as likely to be active users of electronic cigarettes than those without such conditions. But the study said most people in both groups gave the same reason for using e-cigarettes: They want to quit smoking.

Researchers at the University of California San Diego School of Medicine, who published the study Tuesday in the online journal Tobacco Control, said they found that people who live with depression, anxiety or other mental health conditions were twice as likely to have tried e-cigarettes and three times more likely to be current users.

In general, the prevalence of smoking in people with mental health conditions is estimated to be around 70 percent greater than among people without them, the study said.

It did not specifically address reasons for this, but there are several theories on the issue. In a 2009 "toolkit for health providers," researchers from the University of Colorado list a variety of factors that may explain the difference.

One possibility is biological; the toolkit says "people with mental health conditions have unique neurobiological features that may increase their tendency to use nicotine." It also raised the possibility that nicotine "affects the actions of neurotransmitters" in the brain. The toolkit also said other psychological and social factors may also contribute.

In the report published Tuesday, the authors said this is the first study to disprove the widely-held notions that people who have a mental health condition and smoke do not have an interest in quitting or are not capable of doing so, and that quitting may have a negative effect on their mental health.

The researchers also found that people with mental health conditions were more likely to want to try e-cigarettes in the future, believing that this might help them quit smoking. The Food and Drug Administration (FDA) has not approved the devices for use as a tool to quit smoking.

"The faces of smokers in America in the 1960s were the 'Mad Men' in business suits," lead author Sharon Cummins, a UC San Diego assistant professor in the Department of Family and Preventive Medicine, said in a news release. "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."

The study also says that researchers now recognize that people with mental health conditions may need specialized treatment in order to help them quit smoking.

The study surveyed 10,041 people and was based on the smoking history of Americans, their efforts to quit smoking, and usage and perceptions of e-cigarettes. Respondents were also asked if they had ever been diagnosed with a mental health condition.

Of those surveyed, 60.5 percent of smokers with a self-reported mental health condition said they would likely try e-cigarettes in the future; only 45.3 percent of smokers who did not report such conditions said they would be likely to try the devices.

Researchers estimated that cigarettes purchased by people with psychiatric disorders account for between 30 and 50 percent of all U.S. cigarette sales annually, according to the news release about the study.

Data from the report, which was funded by the National Cancer Institute, shows that a little over half of e-cigarette users surveyed – 51.2 percent – said they believed the devices were safer than regular cigarettes.

"There is nothing deadlier than a standard cigarette," Cummins said. "If someone is a regular smoker, they are better off with an e-cigarette. But that’s almost a false choice, because a lot of people feel that smokers who felt pressure to quit may not quit now, because they’ll keep smoking the e-cigarette."

One of the biggest concerns people have expressed about e-cigarettes is that the devices would challenge growing social consensus that smoking is unacceptable – but Cummins said this has not happened.

"So far, nonsmokers with mental health disorders are not picking up e-cigarettes as a gateway to smoking," Cummins said. But he added: "Since the safety of e-cigarettes is still unknown, their use by nonsmokers could put them at risk."

Cummins said the most important finding is that people with mental health conditions are often seeking a way to kick the habit.

"People who have mental health conditions [and smoke] want to quit, deserve the help to quit and are seeking ways to help them quit," he said.