Some people believe that vaping and smoking hookah could possibly be gateways to teens eventually using marijuana. And it turns out, they're not entirely incorrect.

A new study found that teenagers who vape or smoke hookah are more likely to use marijuana in later years than teens who did not. Researchers took a survey of over 2,600 public high school students in Los Angeles back in 2013 when they were going into their freshman year. The kids were asked if they used e-cigarettes, hookah or other tobacco products as well as marijuana. Two years later they were surveyed again about the same substances. They found that the kids who used e-cigarettes as freshman were three times more likely to use marijuana two years later than kids who did not vape. Kids who used hookah as freshman were four times more likely to use marijuana two years later.

The researchers pointed out that there isn't necessarily a causal link between vaping or hookah and future marijuana use. There are a number of factors that could lead teens to eventually use cannabis.

The study also didn't measure the frequency of marijuana use. The survey simply asked if the students had used marijuana within the last 30 days. So just because a kid vaped or used hookah doesn't mean they necessarily became regular marijuana users later.

The researchers weren't necessarily trying to make an anti-marijuana point either. They were simply showing that while the number of young people smoking cigarettes is reaching all time lows, the number of teens and young people use tobacco products is actually increasing. And that while these new forms may be less dangerous than cigarettes, they still carry health risks that people should know about.

(h/t CNN)