Prevalence of high school seniors' marijuana use is expected to increase with legalization

Now, a study published in the International Journal of Drug Policy by researchers affiliated with New York University's Center for Drug Use and HIV Research (CDUHR), finds large proportions of high school students normally at low risk for marijuana use (e.g., non-cigarette-smokers, religious students, those with friends who disapprove of use) reported intention to use marijuana if it were legal.

The study, "Correlates of Intentions to Use Cannabis among US High School Seniors in the Case of Cannabis Legalization," used data from Monitoring the Future (MTF), a nation-wide ongoing study of the behaviors, attitudes, and values of American secondary school students. The researchers found that ten percent of non-lifetime marijuana users surveyed by MTF reported that they would try marijuana if legal.

"Our study focused on intention to use and it was the first to find that groups generally not "at risk" become more "at risk" when legalized," said Joseph J. Palamar, PhD, MPH, Assistant Professor at the Department of Population Health, NYU Langone Medical Center.

The researchers examined the most current attitudes, focusing on cohorts from 2007-2011. The data were collected prior to the legalization of recreational marijuana use in Colorado and Washington, but after legalization of medical marijuana was pending or enacted in up to 16 states.

Data were analyzed separately for the 6,116 seniors who reported no lifetime use of marijuana and the 3,829 seniors who reported lifetime use (weighted samples). The researchers looked at whether demographic characteristics, substance use and perceived friend disapproval towards marijuana use were associated with 1) intention to try marijuana among non-lifetime users, and 2) intention to use marijuana as often or more often among lifetime users, if marijuana was legal to use.

"Assuming that onset use would occur before or during the senior year, the study's results suggest that this would constitute a 5.6% absolute increase in lifetime prevalence in this age group, rising from 45.6% to 51.2%," said Dr. Palamar. "However, lifetime prevalence increases as adolescents age into adulthood. So by age 26, 64% of young adults in the US are expected to use marijuana in their lifetime in the current policy context. We don't know whether those found to be at risk in this study are the same adolescents that are going to use at an older age regardless of legal status."

Not surprisingly, odds for intention to use outcomes increased among groups already at high risk for use (e.g., males, whites, cigarette smokers) and odds were reduced when friends disapproved of use. However, large proportions of subgroups of students normally at low risk for use (e.g., non-cigarette-smokers, religious students, those with friends who disapprove of use) reported intention to try marijuana if legal. Recent use was also a risk factor for reporting intention to use as often or more often among lifetime users.

"What I personally find interesting is the reasonably high percentage of students who are very religious, non-cigarette smokers, non-drinkers, and those who have friends who disapprove of marijuana use -- who said they intended to try marijuana if it was legal," said Dr. Palamar. "This suggests that many people may be solely avoiding use because it is illegal, not because it is "bad" for you, or "wrong" to use."

The researchers caution that as marijuana use increases, regardless of legal status, it will become increasingly important to prevent adverse consequences that may be associated with use. Public health practitioners must continue to educate marijuana users and those at risk for initiation and/or continued use about the potential harms associated with use. Likewise, the researchers stress the need to address drug use through more of a public health paradigm and treat use as a health issue and less of a moral issue.