Adolescents who use both marijuana and alcohol during middle school and high school are more likely to have poor academic performance and mental health during high school, according to a new study by the nonprofit RAND Corporation that followed a group of students over a seven-year period.
However, the study found marijuana use was predictive of poorer functioning across more areas, including lower academic functioning, being less prepared for school, more delinquent behavior and poorer mental health. The results are published online in the journal Addiction.
Findings also show that when youth are using alcohol and marijuana at the same level, nonwhite youth tend to experience poorer functioning than white youth. For example, Asian and multiethnic youth reported more physical health problems than white youth.
Among those using alcohol and marijuana at the same level, Asian, black and Hispanic youth reported being less prepared academically than white youth and Hispanic and multiethnic youth reported lower academic performance than white youth.
"Disparities are occurring as early as high school and therefore it is crucial to address alcohol and marijuana use early on, especially for nonwhite youth," said Elizabeth D'Amico, lead author of the study and senior behavioral scientist at RAND. "One approach may be to increase protective factors such as parental support or the adolescent's ability to resist temptations to use these substances."
The study focuses on two groups of adolescents who were asked to complete seven surveys between 2008 and 2015. The first survey was administered when the adolescents were in sixth or seventh grade. A total of 6,509 youths responded to at least two waves of the survey.
The participants all took part in an alcohol and other drug use prevention program called CHOICE that was conducted in 16 middle schools in the greater Los Angeles area. As the participants moved on to high school, researchers continued to survey the students about their drug use and academic progress.
"Many youth tend to think that alcohol use has more consequences than marijuana use and therefore view marijuana use as safer than drinking," D'Amico said. "However, youth need to better understand the harms of marijuana use, such as the potential effect on their developing brain and how it can affect performance in both adolescence and adulthood."
Although white youth appear to experience less negative effects from alcohol and marijuana use, the survey responses indicate that white youth are at a higher risk for alcohol and marijuana use during middle school and high school.
Researchers note there are other preexisting factors that are not included in the current study that could have potentially contributed to either alcohol or marijuana use or the level of functioning during the period studied. Those factors include racial discrimination, parental involvement or neighborhood quality.
Support for the study was provided by the National Institute on Alcohol Abuse and Alcoholism. Other authors of the study are Joan S. Tucker, Jeremy N.V. Miles, Brett A. Ewing, Regina A. Shih and Eric R. Pederson.
RAND Health is the nation's largest independent health policy research program, with a broad research portfolio that focuses on population health, health care costs, quality and public health systems, among other topics.