A new study has found the teenagers who used e-cigarettes and hookah were more likely to use cannabis later. The study, conducted by researchers from the University of Southern California and the University of Pennsylvania, was published in the journal Pediatrics this week.
Researchers surveyed 2,668 students from 10 public high schools in Los Angeles starting fall 2013, when these students were still in ninth grade and 14 years old.
The students answered a survey on paper, by phone, or via internet on whether they had used e-cigarettes, combustible cigarettes, or hookah water pipes in the past 30 days. They were also asked if they had consumed any type of cannabis product.
A follow-up survey on these students were held in the fall of 2015. This time, the students were now 16 years old and in 11th grade. They were asked whether they had used three forms of cannabis products: valed, edible, of combustible.
The researchers found that the students who had tried e-cigarettes when the survey started are more likely, by more than three-fold, to use marijuana compared to those who had not tried e-cigs.
The researchers controlled for certain factors that may be associated with an increased risk of cannabis use. These factors include family history of tobacco and pot use, depression, peer use, and impulsivity.
Dr. Ana Navas-Acien, however, cautioned that their findings do not mean that the association is causal. Navas-Acien, who is a professor of Columbia University;s environmental health sciences, was not involved in the study.
According to her, people need to be very careful about interpreting these kind of relationships. She noted, though, that the use of e-cigarettes and combustible cigarettes seems to precede marijuana use somehow.
Meanwhile, students who had used hookah at the start of the survey had more than three-fold increase in the likelihood of having used or using cannabis two years later. They also had over a four-fold increase in the likelihood of their using cannabis in the previous 30 days.
Navas-Acien pointed out that one potential reason for the strong link between hookah and cannabis use is that hookahs enable users to mix multiple combustible products together and could be used with cannabis itself.