Racial differences in trajectories of heavy drinking and regular marijuana use from ages 13 to 24 among African-American and White males
Introduction
The probability of substance use gradually increases during adolescence, peaks in the late teens or early 20s, and slowly declines thereafter (Chen and Kandel, 1995, Johnston et al., 2009b, White and Jackson, 2004/2005). Few studies, though, have examined racial differences in developmental patterns of substance use, despite research showing significant differences in the prevalence of substance use between African-American and White adolescents (Lee et al., 2010, Wallace et al., 2003). Whereas African American adolescents drink less alcohol than their White peers (Godette et al., 2009, Pascall et al., 2005), among those African Americans who drink, heavy drinking and alcohol abuse peak later and persist longer than for Whites (Cooper et al., 2008, White and Jackson, 2004/2005). In contrast, prevalence rates of marijuana use are generally similar for African American and White youth (Brown et al., 2004).
It is important to examine salient patterns of alcohol and marijuana trajectories during the transitional period from adolescence to young adulthood for African Americans and Whites because racial differences in the timing of heavy drinking and regular marijuana use, as well as maturational processes, may be uniquely observable during this period. However, few studies have examined racial differences in developmental trajectories of alcohol and marijuana use from adolescence into young adulthood, despite research showing that substance use habits change substantially in the early twenties (Johnston et al., 2009a). Two articles reporting on one study examined racial differences in trajectories of alcohol and marijuana use (Brown et al., 2004, Flory et al., 2006, respectively) using data collected annually from the 6th to 10th grade and again at age 20. The alcohol use trajectories showed three-class solutions for both African Americans and Whites, though their patterns differed in timing of onset and increases as well as in intensity (Flory et al., 2006). A three-class solution fit best for marijuana use trajectories for both African Americans and Whites but again there were clear race differences in levels and shapes (Brown et al., 2004). These studies, which were the only ones to examine trajectories of alcohol and marijuana use separately by race, showed that developmental patterns of alcohol and marijuana use were not the same for African-American and White adolescents. Tucker et al. (2003) examined trajectories of binge drinking from ages 13 to 18. Although the authors did not analyze trajectories separately by race, they found race differences in the proportions across groups; African Americans were more likely to belong to the nonbinging and increasing groups, whereas Whites were less likely to belong to the nonbinging group. The question remains, however, whether patterns converge or diverge more for African-American and White youth as they transition from adolescence into young adulthood. As Brown et al. (2004) and Flory et al. (2006) pointed out, their results were limited because data were not collected beyond age 20 and there was a gap in annual data from the 10th grade through age 20, which is a very important developmental period for increases in alcohol and marijuana use (Chen and Kandel, 1995). The present study extends this research by using annual data from ages 13 to 24, and thus, expanding the follow-up period to the end of emerging adulthood.
There have been some studies which have examined trajectories of heavy drinking and marijuana use for individuals during emerging adulthood but none examined trajectories separately for African Americans and Whites. Schulenberg et al., 1996, Schulenberg et al., 2005 examined race/ethnicity as a predictor of trajectory group membership. Using four waves of national data from ages 18 to 24, Schulenberg et al. (1996) identified six trajectories of frequent heavy drinking (5+ drinks in a row at least twice in the last two weeks): never, rare, developmentally limited (decreased), late-onset (increased), chronic, and “fling” (those who were low at the first and last waves but higher in the middle). White men, compared to non-White men, were more likely to be in the chronic vs. decreased group and White women, compared to non-White women, were more likely to be in the increased vs. rare, increased vs. fling, chronic vs. increased, decreased vs. rare, and decreased vs. fling groups. Schulenberg et al. (2005) identified the same six groups for frequent marijuana use (3+ times in the past month and/or 20+ times in the past year). They found that African Americans, compared to Whites, were less likely to be in the chronic, decreased, fling, and rare groups and more likely to be in the never group. Although these two studies identified distinct trajectories of alcohol and marijuana use during emerging adulthood and some racial differences, they did not include data prior to age 18. Thus, they were not able to examine differences in trajectories characterized by early onset use or by rapid increases in use during adolescence. Ellickson et al. (2004) identified five trajectory groups for marijuana use frequency from ages 13 to 23: abstainers, occasional light users, early highs, steady increasers, and stable light users. Although they did not compare trajectories across race, within race, African Americans were most likely to be stable light users and Whites were most likely to be steady increasers and stable light users. Like previous studies (i.e., Brown et al., 2004, Flory et al., 2006), there was a substantial gap in data collection (no data were collected between ages 18 and 23). Thus, fluctuations in patterns during this important developmental period may have been missed.
The current study aims to address gaps in the literature by examining between- and within-race heterogeneity in developmental patterns of heavy drinking and regular marijuana use in a community sample of young men who were followed annually from early adolescence through their mid-20s. We focus on heavy drinking and regular marijuana use rather than any use to describe developmental patterns that may be implicated for adult alcohol and marijuana use disorders.
Section snippets
Participants
The sample came from the Pittsburgh Youth Study (PYS), a longitudinal study of adolescent males enrolled in the City of Pittsburgh, PA, public schools in 1987, which oversampled high-risk boys. Students in 7th grade were screened for antisocial behavior and approximately 250 boys who were in the top 30% for antisocial behavior risk and 250 from the remainder of the sample were selected for follow ups (n = 506). Details of the larger study are described in Loeber et al. (2008). These analyses were
Descriptive statistics
Descriptive statistics for heavy drinking and regular marijuana use at each age are displayed in Table 1. Whites, compared to African Americans, were significantly more likely to be heavy drinkers at every age. A significant race difference in regular marijuana use was observed only at ages 23 and 24 when Whites were less likely than African Americans to regularly use marijuana.
Total sample
A series of models with an increasing number of groups was evaluated for model fit. The four-group solution fit best
Discussion
The current study sought to enhance our understanding of developmental patterns of substance use by examining racial differences in trajectories of heavy drinking and regular marijuana use among males transitioning from adolescence into young adulthood. Our findings are consistent with other studies indicating that heavy drinking is more prevalent among Whites than African Americans at least during adolescence and the early 20s (Lee et al., 2010, O’Malley and Johnston, 2002). African Americans
Role of funding source
This research was supported, in part, by grants from National Institute on Alcohol Abuse and Alcoholism (ARRA R01 AA016798, AA019511), National Institute of Mental Health (P30 MH079920; R01 MH73941), National Institute on Drug Abuse (R01 DA 411018), the Office of Juvenile Justice and Delinquency Prevention (OJJDP 2005-JK-FX-0001; 96-MU-FX-0012), and the Department of Health of the Commonwealth of Pennsylvania. Points of view in this document are those of the authors and do not necessarily
Contributors
Authors Andrea Finlay and Helene White designed the present study and wrote the manuscript. Author Andrea Finlay conducted the analyses with statistical guidance from authors Eun-Young Mun and Chioun Lee, who also contributed to the final editing of the paper. Author Courtney Cronley contributed to the literature review and the writing of the manuscript. All authors contributed to and have approved the final manuscript.
Conflict of interest
No conflict declared.
Acknowledgements
We thank Kristen McCormick and Rebecca Stallings for their assistance in preparing the data files. An earlier version of this paper was presented as a poster at the Society for Research on Child Development annual meeting, March 2011, Montreal, Canada.
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