By Matt Wood
Substance use among adolescents and young adults in the United States is a perennial problem. Despite decades of campaigns by health care providers, schools and the government warning about the dangers of alcohol, tobacco and marijuana, substantial numbers of young people still report using these substances on a regular basis.
Research has shown that substance use increases from early to late adolescence, peaks around the mid-20s and declines thereafter, but is that pattern of use the same for everyone? A recent study by researchers from the Department of Psychiatry and Behavioral Neuroscience at the University of Chicago Medicine looked at a nationally representative sample of youths in the United States and found distinct gender and racial differences in the developmental trajectories of various types of substance use from early adolescence to young adulthood. This suggests opportunities for more targeted intervention and prevention programs.
Pan Chen, Ph.D and postdoctoral scholar, and Kristen Jacobson, Ph.D and associate professor in psychiatry and behavioral neuroscience, wanted to get a true picture of how substance use changes over time for young people in the United States, from early adolescence all the way through adulthood. Previous studies on substance use were generally not nationally representative, meaning they didn’t reflect the gender and racial makeup or substance use behaviors of youths in the entire country. Studies that did use nationally representative data focused on shorter periods of time, such as early to late adolescence only.
Using a large sample of more than 20,000 participants in the National Longitudinal Study of Adolescent Health, Chen and Jacobson were able to measure substance use in students from 12 years old all the way up to 34-year-old adults. “This is important because when you are focusing on a nationally representative sample, you will be better able to generalize your findings to the population of adolescents in the US,” Chen said.
The data also included four types of substance use: alcohol use, heavy or binge drinking, cigarette smoking and marijuana, making it the first study to compare developmental patterns of these different behaviors simultaneously. The study was published in the Journal of Adolescent Health.
In their analyses, Chen and Jacobson found that patterns for all four types of substance use held to the typical curve, increasing from early adolescence to the mid-20s and then tapering off. But they found some important differences as well. First, while females reported higher substance use in early adolescence, males’ substance use behaviors increased at a significantly faster rate and peaked at a much higher level from middle adolescence to young adulthood. Hispanic youths displayed higher rates of use than other groups at age 12, but Caucasians peaked at much higher levels in their 20s. All racial groups tapered off to roughly the same levels by age 34 except for African Americans, who reported higher levels of cigarette smoking and marijuana use into adulthood.
Understanding these differences offers insight into how and when to intervene with different groups of young people. “This type of project is important because it provides crucial implications for intervention and prevention projects,” Chen said. “It offers insights into critical time periods, as well as the target population.”
Jacobson says that while their findings parallel those of previous studies, the additional data on racial differences adds another dimension. “What’s interesting is over and over again, minorities are usually at lower risk for a lot of problem behaviors, despite worse contexts. Yet they are overrepresented in adulthood in certain types of disorders, especially substance use disorders,” she said. “Is there something different about the biology? Is it something different about social norms for these behaviors or the stress of the environmental context? It’s really unclear what’s causing these differences at this point.”
Chen and Jacobson are currently working on a new study that drills into the data for even more distinctions by examining the effect of college education on substance use between Caucasians and African Americans. The more fine-grained distinctions they can find between various groups of young people, the better they can focus on understanding the causes, whether they are biological, social or environmental.
“If we can get access to data that will enable us to further explain why there are racial differences in developmental patterns of substance use, that would be even more interesting,” Chen said.
Chen, P., & Jacobson, K. (2012). Developmental Trajectories of Substance Use From Early Adolescence to Young Adulthood: Gender and Racial/Ethnic Differences Journal of Adolescent Health, 50 (2), 154-163 DOI: 10.1016/j.jadohealth.2011.05.013