Teen substance abuse has always been a topic of concern for scientists and parents alike, but a recent study from researchers at Penn State have found a new and fascinating trend. Cigarette and alcohol use seems to be on the decline, according to statistics, but marijuana use is increasing. Specifically, researchers have found more of an increase in marijuana use among African American teenagers. They are now wondering if recent trends in marijuana legalization for both medical and recreational use have anything to do with this jump.

“Our analysis shows that public health campaigns are working — fewer teens are smoking cigarettes,” said Stephanie Lanza, professor of biobehavioral health at Penn State, in a recent press release. “However, we are surprised to find the very clear message that kids are choosing marijuana over cigarettes.”

Collecting data on substance use among high school seniors from the years 1976 and 2013, Lanza and her team were able to pool from surveys on over 600,000 students in a project known as Monitoring the Future, a long-term, epidemiological study conducted by the University of Michigan. Honing in on usage of alcohol, cigarettes and marijuana specifically, Lanza and her colleagues analyzed how use has changed in the past 37 years, and reported their results in the Journal of Adolescent Health.

For the project, students were asked 30 days before the survey about their personal marijuana, cigarette, and alcohol use. Ultimately, researchers observed a significant decrease in cigarette use, specifically among Caucasian teenagers during this period, while finding an increase in marijuana use, particularly among African-American teens.

This trend seemed to change as time went by. In 1993, researchers observed that black adolescents were just as likely to use marijuana as they were to use cigarettes, while the trend toward cigarette use seemed to wane and marijuana use only increased. In the case of white adolescents, this group was more likely to use cigarettes until about 2011, when marijuana use began to slightly surpass cigarette use. 2013 saw more of a statistical difference among marijuana and cigarette use, as 19 percent of white teens reported smoking cigarettes, while 22 percent reported using marijuana. Among black teens there was more of a gap, as 10 percent reported smoking cigarettes, while 25 percent admitted to using marijuana.

As far as alcohol consumption goes, researchers saw an overall decrease in use since the mid-1970s, but still found that alcohol was the most popular substance among white adolescents. Consistently throughout the study, alcohol use among white teens remained higher than among black teens.

Researchers also found a correlation between cigarette use and marijuana use, as teens were more likely to use marijuana if they also smoked cigarettes, and vice versa. Increased alcohol use correlated to increased marijuana use among teens as well.

The study was quantified in line graphs to track how substance use has changed over the past few decades.

“What will this look like in a few years?” Lanza asked, referencing the two lines on the graph plotting alcohol and marijuana use among black teens. “All signs point to these two lines crossing within the next few years. This is a decisive shift.”

The next step, according to researchers, is to observe why this shift has taken place. Currently, they are particularly interested in how recent dialogue shifts on the negative aspects of cigarettes, but the growing acceptance of marijuana has caused this change. Specifically, they hope to examine how the rise of legalization in several states has affected marijuana use in teens.

Source: Lanza S, Vasilenko S, Butera N, et al. Trends Among U.S. High School Seniors in Recent Marijuana Use and Associations With Other Substances: 1976–2013. Journal of Adolescent Health. 2015.