The spliff. Other than the size of our cars and the width of our toilet seats, one of the big differences between Americans and our European sisters and brothers across the pond is how we consume our cannabis, and what we consume it with. While relatively few Americans roll their weed up with tobacco, the spliff is the primary weed consumption vehicle for E.U. potheads.

The most recent Global Drug Survey reports that, while only 8 percent of cannabis consumers in the U.S. mix tobaccy in with their wacky, the majority of Europeans do: 77 percent in the UK, 89 percent in the Netherlands, and 94 percent in Italy.

With all that weed and tobacco comingling, a few researchers in England found that very little was actually known about how tobacco affects the effects of cannabis. “Surprisingly little research has been done on how tobacco might alter the effects of cannabis,” the study’s lead author, clinical psychologist Chandni Hindocha, told University College London. “As cannabis gets legalized in more countries, it is essential that any changes in cannabis policy consider their interrelationship.”

And what is that interrelationship? It works on a few different levels. While inhaling tobacco with weed didn’t seem to affect the high (in terms of euphoria and groovy good vibes), it did affect both cognitive impairment from smoking weed and the physiological reaction from smoking.

While smoking cannabis by itself was found to impair both verbal memory (remembering passages read to them before smoking) and working spatial memory, smoking a cannabis/tobacco combo fatty lessened that cognitive slowness. Nicotine, the researchers said, improves concentration. Essentially, after you smoke a spliff the weed and tobacco fight over whether to sharpen or dull your memory.

This push-pull effect of the cannabis/tobacco mixture can also be felt in the heart and blood pressure. Adding tobacco to a sesh increased the participant’s blood pressure and heart rate by a moderate amount. The authors of the study said this could mean that a spliff is worse for your cardiovascular system than a pure flower joint.

“There is a clear public health implication here, suggesting that smoking tobacco with cannabis does not improve the stoned feeling but is still worse for physical health,” said Val Curran, a clinical pharmacology professor who also worked on the study.

Photo via Flickr user Chuck Grimmett