E-cigarettes seem to cause constant controversy. On one hand, you'll hear (probably from someone who vapes) that smoking e-cigarettes is a healthy way to knock cigarettes for good. On the other hand, you'll hear that they're just as bad as regular cigarettes, especially if you overdo it. Then you've got plenty of in-betweeners saying that, hey, vaping is better than those old-fashioned, lung-shriveling cancer sticks, but the jury's still out on just how freely you can use the word "healthy" to describe it.

Since vaping is still relatively new, there aren't many conclusive, long-term studies to back either side of the argument. But new research shows that e-cigarettes with nicotine (an important detail) can cause a temporary rise in users' blood pressure and heart rate, along with increased arterial stiffness. That stiffness forces your heart to work harder to pump blood, which can increase your risk of heart attacks and strokes in the long term.

Call us crazy, but we wouldn't consider something that might put people at a higher risk of heart attacks to be "harmless" or "healthy".

The research, presented at the European Respiratory Society International Congress on Monday, showed that when people smoked e-cigarettes with nicotine they experienced three times the arterial stiffness as when they smoked e-cigarettes without nicotine in the first 30 minutes after smoking.

This is the first study that's found e-cigs to cause arterial stiffness, and it's most likely because of the nicotine, according to Dr. Magnus Lundback, a researcher at Danderyd University Hospital at the Karolinska Institute in Stockholm, Sweden.

And while the increase in arterial stiffness was only temporary, that doesn't mean it doesn't have long-term effects on habitual e-cigarette users, says Lundback.

"The same temporary effects on arterial stiffness have also been demonstrated following use of conventional cigarettes," he says, according to Eurekalert. "Chronic exposure to both active and passive cigarette-smoking causes a permanent increase in arterial stiffness. Therefore, we speculate that chronic exposure to e-cigarettes with nicotine may cause permanent effects on arterial stiffness in the long term."

While there currently aren't any studies on the long-term effect that e-cigarettes have on arterial stiffness, these aren't the most promising findings. Lundback's advice is to approach e-cigarettes with caution. Plenty of smokers transition to vaping to quit, and plenty of nonsmokers start vaping because they perceive it as relatively harmless thanks to the way it's marketed. Despite the increase in the number of people picking up the habit, the evidence showing that there are less-than-favorable effects of vaping is growing, Lundback says.

Until there are more long-term studies with definitive results, it's tough to say whether vaping is definitely good, bad, or somewhere in-between. But no matter how much better than actual cigarettes that vape smoke smells, it's evidently not as harmless as it seems, and the only surefire way to avoid negative repercussions is to kick smoking altogether.