Drug Abuse Prevention

Research Findings from February, 2005 Director's Report

This section lists selected summaries from NIDA funded research projects that investigate youth drug abuse prevention. The summaries provided were selected from recent issues of the Director's Report to the National Advisory Council on Drug Abuse. For a more comprehensive listing of NIDA funded projects see the Director's Report.

Cigarette Access for Minors Has Been Declining, But Remains High

Investigators from the Monitoring the Future Study examined trends in middle and high school students' perceived ease, methods, and locations of access to cigarettes, and assessed differences related to their sociodemographic characteristics and smoking status. Annual data from nationally representative samples of 8th-, 10th-, and 12th-grade students were analyzed for the 1997-2002 period. Analyses revealed that perceived ease of access decreased significantly among never and past smokers. Decreased individual purchasing in retail outlets, as well as decreased purchasing from vending machines, were reported by 8th- and 10th-grade students. All grades reported decreased purchasing from self-service placements of cigarettes. Decreases in access were not reported across all retailer types, and no significant increases were seen in the percent of underage purchasers who reported being asked to show identification. Both gender and ethnicity were significantly related to where and how underage youth reported obtaining cigarettes. Findings show that: (1) cigarette access for minors has been declining, but remains high; (2) perceived access to cigarettes clearly increases with level of smoking; and (3) policies to reduce such access may be having an impact as evidenced by decreased retail and vending machine purchases and self-service purchases. The authors conclude that states should continue to strengthen efforts to reduce youth cigarette access, especially in the areas of confirming buyer age via identification checks, and should make efforts to decrease access across all retailer types. Johnston, L.D., O'Malley, P.M., and Terry-McElrath, Y.M. Methods, Locations, and Ease of Cigarette Access for American Youth, 1997-2002. American Journal of Preventive Medicine, 27, pp. 267-276, 2004.

The Motivation, Skills, and Decision-Making Model of Drug Abuse Prevention

This article summarizes the theoretical basis for targeted prevention programs as they apply to different high-risk groups. The authors explain the advantages and disadvantages of different definitions of risk and discuss strategies for preventing drug use related problems in high-risk youth. Productive prevention programs for many at-risk groups share similar components, including those that address motivation, skills, and decision making. Key aspects of these three components are examined and linked to theories in clinical psychology, social psychology, sociology, and chemical dependence treatment. Among a total of 29 promising targeted prevention programs, the authors describe examples of empirically evaluated, intensive interventions that have made a positive impact on the attitudes and behavior of multiple problem youth. Incorporating the perspectives of multiple disciplines appears essential for progress in drug abuse and o ther problem behavior prevention. Sussman, S., Earleywine, M., Wills, T., Cody, C., Biglan, T., Dent, C. W. and Newcomb, M. D. The Motivation, Skills, and Decision-making Model of Drug Abuse Prevention. Substance Use and Misuse, 39, pp. 1971-2016, 2004.

Barriers to Intervention Among Young MDMA/Ecstasy Users

In the past several years, the use of MDMA ("Ecstasy") has increased substantially in the U.S. and in many countries around the world. Although this increase has been associated with the dance club and rave scenes, MDMA use has also expanded into new settings, and the diversity of users has grown. Given the increasing, although as yet unclear, evidence that MDMA is potentially neurotoxic and may lead to adverse psychological consequences, understanding how active users perceive the risks associated with MDMA can help to inform prevention and intervention approaches. Based on audiotaped focus groups and individual interviews conducted with 30 users in Central Ohio, this study found that, beyond the risk of obtaining something potentially deadly instead of MDMA, most users minimize or discount potential risks of neurotoxicity or psychological problems from MDMA use. As more people use MDMA without developing obvious adverse consequences, and others observe their "benign" experiences as meaning that MDMA is not a harmful drug, the more that others may in turn be willing to use it. Participants in this study appeared to want information on the risks associated with MDMA use so they could make their own decisions about future use. Because MDMA is often used among small groups of friends, providing accurate information to peer leaders about MDMA, who can then disseminate the information to their peers, may be a promising approach for discouraging potential users from doing so. Carlson, R., Falck, R., McCaughan, J., and Siegal, H. MDMA/Ecstasy Use Among Young People in Ohio: Perceived Risk and Barriers to Intervention. J Psychoactive Drugs, 36, pp. 181-189, 2004.

Age at First Use and Psychopathology as Risk Factors for Substance Use Disorder

This paper explores the issue of early drug use as a risk factor for adolescent substance use disorder (SUD), and the possible role of comorbid conduct problems in explaining this association. Sophisticated statistical tests were applied to longitudinal data from a large population-based sample, the Great Smoky Mountains Study, assessed annually between ages 9 and 16. Of note, drug use before age 13 was a strong predictor of transition to SUD, and early use remained a risk factor even in the absence of conduct disorder. Boys with a history of depression were at increased risk for SUD, and girls with anxiety experienced an increased risk at age 16. Findings from such large population-based studies can help target populations at higher risk for drug abuse for appropriate preventive interventions. Sung, M., Erkanli, A., Angold, A., and Costello, E.J. Effects of Age at First Substance Use and Psychiatric Comorbidity on the Development of Substance Use Disorders. Drug and Alcohol Dependence, 75, pp. 287-299, 2004.

Smoking Among New Yorican Adolescents

The authors identified longitudinal relationships between early risk and protective factors from the domains of family, personality, and peer influences and later tobacco use in Puerto Rican adolescents living in New York. Aspects of the ethnic minority experience as moderators of familial risk and protective factors were investigated. Participants were 282 female and 276 male Puerto Rican adolescents interviewed twice, 5 years apart. The authors used hierarchical regression analyses to identify a model with direct and indirect paths. Family, personality, peer, and early smoking domains were directly related to later adolescent smoking. Partial mediation occurred. The authors identified risk-protective and protective-protective interactions between variables from the ethnic minority experience and family domains. Interventions to reduce smoking among Puerto Rican adolescents should focus on multiple contexts, including aspects of the ethnic minority experience. Brook, J.S., Pahl, T., Balka, E.B, and Fei, K. Smoking Among New Yorican Adolescents: Time 1 Predictors of Time 2 Tobacco Use. Journal of Genetic Psychology, 165, pp. 324-340, 2004.

School-Based Drug Abuse Prevention Program on Adolescent Risky Driving

To determine whether a large-scale randomized trial of a school-based drug abuse prevention program during junior high school led to less risky driving among high school students, researchers examined Department of Motor Vehicles data including the total number of violations on students' driving records as well as the number of "points" that indicate the frequency and severity of the violations. Controlling for gender and alcohol use, students who received the drug prevention program during junior high school were less likely to have violations and points on their driving records relative to control group participants that did not receive the prevention program. Anti-drinking attitudes mediated the effect of the intervention on driving violations but not points. These results suggest that the behavioral effects of competence-enhancement prevention programs can extend to risk behaviors beyond the initial focus of the intervention, such as risky driving. Griffin, K.W., Botvin, G.J. and Nichols, T.R. Long-Term Follow-Up Effects of a School-Based Drug Abuse Prevention Program on Adolescent Risky Driving. Prevention Science, 5(3), pp. 207-212, 2004.

Preventing Substance Use and Disordered Eating

This article assesses the efficacy of a school-based, sport team-centered program to prevent young female high school athletes' disordered eating and body-shaping drug abuse. The ATHENA (Athletes Targeting Healthy Exercise and Nutrition Alternative) curriculum's 8 weekly 45-minute sessions were incorporated into a team's usual practice activities. Content was gender-specific, peer-led, and explicitly scripted. Experimental athletes reported significantly less ongoing and new use of diet pills and less new use of athletic-enhancing substances (amphetamines, anabolic steroids, and sport supplements). Other health-harming actions were also reduced (e.g., riding with an alcohol-consuming driver, failure to use seat belts, and new sexual activity). ATHENA athletes had positive changes in strength-training, self-efficacy and healthy eating behaviors. Thus, sport teams are effective natural vehicles for gender-specific, peer-led curricula to promote healthy lifestyles and to deter disordered eating, athletic-enhancing substance use, and other health-harming behaviors. Elliot, D.L., Goldberg, L., Moe, E.L., DeFrancesco, C.A., Durham, M.B., and Hix-Small, H. Preventing Substance Use and Disordered Eating: Initial Outcomes of the ATHENA (Athletes Targeting Health Exercise and Nutrition Alternatives) Program. Archives of Pediatric Adolescent Medicine, 158, pp. 1043-1049, 2004.

Two Prevention Programs Reduce High Risk Behaviors Among African American Boys

This study was designed to test the efficacy of two programs to reduce high-risk behaviors, including drug use, delinquency, and high risk sexual behavior, among inner-city African-American youth. Students in grades 5 through 8 and their parents and teachers in twelve metropolitan Chicago schools were involved in a cluster randomized trial. The preventive interventions being tested were 1) a social development curriculum, focusing on social competence skills, and 2) a school/community intervention, consisting of the social development curriculum plus a school-wide climate and parent/community intervention. The control group received an attention-placebo. For boys, both programs significantly reduced violent behavior, provoking behavior, school delinquency, drug use, and recent sexual intercourse. The rate of condom use was increased among boys as well. The school/community intervention was significantly more effective than the curriculum-only intervention in reducing risk based on examination of a combined behavioral measure. There were no significant effects for girls. Flay, B.R., Gramlich, S., Segawa, E., Burns, J.L., and Holliday, M.Y. Effects of Two Prevention Programs on High Risk Behaviors among African American Youth. Archives of Pediatric and Adolescent Medicine, 158, pp. 377-384, 2004.

One-Year Outcomes of The Coping Power Program

The Coping Power Program randomly assigned at-risk aggressive preadolescent boys during the transition from elementary school to middle school to receive the Coping Power child component, the Coping Power Program parent and child components, or a control condition. Results indicated that both Coping Power intervention conditions produced lower rates of covert delinquent behavior and of parent-rated substance use at the 1-year follow-up compared to the control group. Moreover, the intervention effects were most apparent for the combined Coping Power Program parent and child components. Boys also displayed teacher-rated behavioral improvements in school during the follow-up year, and these effects appeared to be primarily influenced by the Coping Power child component. Lochman, J.E. and Wells, K.C. The Coping Power Program for Preadolescent Aggressive Boys and Their Parents: Outcome Effects at the 1-Year Follow-Up. Journal of Consulting and Clinical Psychology, 72(4), pp. 571-578, 2004.

Comparison of Telephone and In-Person Delivery of Prevention

This study assesses responses to a preventive intervention to reduce HIV risky behaviors and health practices among young people living with HIV (YPLH) in Los Angeles, San Francisco, and New York over 15 months. YPLH aged 16 to 29 years (n = 175; 26% black and 42% Latino; 69% gay men) were randomly assigned to a 3-module intervention involving 18 sessions delivered by telephone, in person, or a delayed-intervention condition. Intention-to-treat analyses found that the in-person intervention resulted in a significantly higher proportion of sexual acts protected by condoms both overall and with HIV-seronegative partners. Pre- and post-analyses of YPLH in the delayed-intervention condition alone found that YPLH tended to have fewer sexual partners, used fewer drugs, reported less emotional distress, and decreased their use of antiretroviral therapies. Prevention programs can be delivered in alternative formats while retaining efficacy. However, when YPLH are using hard drugs, drug treatment may be needed before delivery of preventive interventions. Rotheram-Borus, M.J., Swendeman, D., Comulada, W.S., Weiss, R.E., Lee, M. and Lightfoot, M. Prevention for Substance-Using HIV-Positive Young People: Telephone and In-Person Delivery. JAIDS, 37 (Suppl 2), pp. S68-S77, 2004.

School District Personnel Hold the Keys to Implementation of Effective Prevention

An important issue in drug abuse prevention programming is the relative roles of school district and school-level decision-makers in the implementation of effective substance use prevention curricula. Drawing on a "Site-Based Management" approach to effective decision-making, it was hypothesized that schools whose personnel played active decision-making roles would be more likely to implement effective curricula than those in which decision-making was the prerogative of school district personnel. Study data comprised 1,369 questionnaires completed by a representative national sample of both district-level prevention coordinators and middle school-based lead prevention teachers. From the perspective of the lead prevention teachers, the school district-level prevention coordinator was more influential than school staff in selecting effective prevention curricula. However, they did find some support for their hypothesis from the district-level informants, who indicated that community groups and advisory committees also play a modest role in the selection of such curricula. Ringwalt, C., Ennett, S.T., Vincus, A., Rohrbach, L.A. and Simons-Rudolph, A. Who's Calling the Shots?: Decision-Makers and the Adoption of Effective School-Based Substance Use Prevention Curricula. Journal of Drug Education, 34(1), pp. 19-31, 2004.

Adapting Prevention to Meet Student Needs

This study examines a variety of characteristics associated with schools, teachers, and the prevention curricula implemented to estimate the proportion of the nation's middle school teachers who adapt substance abuse curricula in response to their students' special problems or needs. Data were collected in 1999 from a representative sample of lead substance abuse prevention teachers in the nation's public and private schools. Almost 80% of respondents report adapting their prevention curricula in response to at least one of the dozen specified student problems and needs. The problems cited most frequently, (over 50% of respondents) were the needs of students who are sexually active or have discipline problems. The two features associated most strongly with adaptations were the recent training of the teacher in the curricula, and substance abuse prevention lessons that could readily be integrated into the school's overall curriculum. Curriculum developers need to recognize the frequency with which, and reasons for curriculum adaptation and include appropriate optional content that addresses students' needs. Ringwalt, C., Ennett, S.T., Vincus, A. and Simons-Rudolph, A. Students' Special Needs and Problems as Reason for the Adaptation of Substance Abuse Prevention Curricula in the Nation's Middle Schools. Prevention Science, 5(3), pp. 197-206, 2004.

Training Youth to Use Leisure Time Wisely Works

The ïTimeWise: Learning Lifelong Leisure Skills' curriculum aims to increase positive use of free time, thereby mitigating/preventing the initiation of substance use. The intervention was delivered to 634 middle school youth in a rural area in eastern United States. Self-report data after one year indicate that students who received TimeWise reported less lack of motivation and more identified and subconscious forms of motivation. TimeWise students reported being better able to restructure boring situations into something more interesting; having higher levels of decision making skills, initiative, community awareness; and participating in new interests, sports, and nature-based activities. Caldwell, L.L., Baldwin, C.K., Walls, T., and Smith, E. Preliminary Effects of a Leisure Education Program to Promote Healthy Use of Free Time. Journal of Leisure Research, 36(3), pp. 310-335, 2004.

Early Intervention Reduces Marijuana Use and Psychopathology in Recent Rape Victims

Nearly 700,000 adult women are raped annually although only one in seven reports the assault to police and receive forensic exams and other professional services. The forensic exam, nevertheless, provides a unique opportunity for a preventive intervention to aid women to cope with potential stress related to the rape-exam procedures and address potential post-rape psychopathology. The intervention implemented with 205 adolescent and adult (15 years and older) female rape victims involved a 17-minute videotape that both explains the forensic exam procedures and uses a cognitive-behavioral approach to reduce anxiety and subsequent PTSD versus standard post-rape treatment control. Sixty percent of the women provided 6-week follow up data. Results indicate that at 6-weeks post exam marijuana use was significantly lower in the video intervention group but that there were no significant differences in rates of abusing alcohol or other drugs. The data also found that the video intervention helped women with a prior assault more than those with no prior assault. Resnick, H., Acierno, R., Kilpatrick, D.G. and Holmes, M. Description of an Early Intervention to Prevent Substance Abuse and Psychopathology in Recent Rape Victims. Behavior Modification, 29(1), pp. 1-33, 2005.

Teaching Theory of Drug Action to Elementary School Children

Recent educational and developmental research suggests that children attempt from an early age to understand the world around them by formulating intuitive theories. The current investigation builds on this literature by examining (1) whether school-age children as young as 8 can learn a theory of drug action that explains the brain's role in mediating drug effects, and (2) whether a causally coherent version of the curriculum is more effective than a less coherent one in changing knowledge and beliefs about alcohol and drug effects, attitudes and intentions toward drug and alcohol use, and actual alcohol use over one year. Participants were 327 grade 3-6 students drawn from 17 classrooms in 3 Catholic schools in an ethnically diverse metropolitan area. Participating schools were chosen on the basis of their socioeconomic and racial diversity. Within each classroom students were randomly assigned to one of 3 groups each of which received one of three curricula developed for this project. Two curricula concerned alcohol and cocaine, and were administered to 110 students each, while the third, a control curriculum about diseases, was administered to 107 children. The "coherent curriculum" was designed to teach the elements of a scientific, brain-mediated theory of drug effects in a causally coherent sequence. The "less coherent curriculum" presented information identical to that in the coherent version; however, sections of the text were reordered so that the consequences of drug use for health and behavior were discussed before the drug's effects. Few differences were found between the two drug and alcohol curricula. However, compared to children receiving the control curriculum both treatment groups demonstrated greater understanding of the circulation of alcohol and cocaine throughout the body, the true long-term effects of these substances, and the stimulant effects of cocaine. Moreover, they had less positive attitudes and intentions toward cocaine. Sigelman, C. K., Rinehart, C. S., Sorongon, A. G., Bridges, L. J., and Wirtz, P. W. Teaching a Coherent Theory of Drug Action to Elementary School Children. Health Education Research, 19, pp. 501-513, 2004.

Infusion-LST Compared to LST as Usual

Findings from the first two years of a study to compare a standard Life Skills Training (LST) program with an infused (I-LST) approach was conducted in 9 small, rural school districts that were randomly assigned to LST, I-LST, or control conditions. Male and female subjects were in grade seven. The LST program significantly reduced alcohol use, binge drinking, marijuana use, and inhalant use after one year for females, and the I-LST program significantly reduced smoking, binge drinking, and marijuana use for females. At the end of the second year the I-LST program continued to impact female smoking, but all other results were non-significant. There were no effects on males at either time point. Smith, E.A. Evaluation of Life Skills Training and Infused-Life Skills Training in a Rural Setting: Outcomes at Two Years. Journal of Alcohol & Drug Education, 48(1), pp. 51-70, 2004.

The Importance of Family-based Prevention Interventions in Rural Areas

There are several reasons to promote the implementation of evidence-based family-focused interventions in rural, small town or micropolitan communities. One key reason is research demonstrating that youth problem behaviors are especially prevalent in rural areas and that these problems can be effectively reduced though family-focused programs. For example, studies have found that rural youth are involved in tobacco, alcohol, and illegal substance use at rates that often exceed those of youth living in urban and suburban communities (America's Children, 2000„Federal Interagency Forum on Child and Family Statistics, 2000; National Institute on Drug Abuse, 1997; Johnston, O'Malley, & Bachman, 2000, 2002). Further, earlier program evaluation research has demonstrated the effectiveness of several evidence-based family-focused programs among rural youth, including the reduction of substance use; related economic analyses also have shown that these programs are cost-beneficial. These programs focus on the enhancement of competencies related to reducing risk and increasing protective factors among families and youth. Meek, J., Lillehoj, C.J., Welsh, J. and Spoth, R. Rural Community Partnership Recruitment for an Evidence-based Family-focused Prevention Program: The PROSPER Project, Rural Mental Health, 29(2), pp. 23-28, 2004.

Predicting Marijuana Use Cessation 5 years after Continuation High School

Cessation from marijuana use five years after completion of continuation high school was predicted by social, attitude, intrapersonal, violence-related, drug use, and demographic baseline measures from 339 high risk teenage marijuana users. Young adult social roles were included as additional predictors. Quitting was defined as no use of marijuana in the last 30 days (42% of the sample at follow-up). Results indicate that baseline level of marijuana use, male gender, young adult marital status, and friends' marijuana use (marginal) remained significant direct predictors of quitting. These results suggest the need to reduce psychological dependence on marijuana and increase social unacceptability of marijuana use across genders to increase prevalence of quit attempts. Sussman, S. and Dent, C.W. Five-Year Prospective Prediction of Marijuana Use Cessation of Youth at Continuation High Schools. Addictive Behaviors, 29(6), pp. 1237-1243, 2004.

The Long-Term Negative Impact of High-Risk Peer Group Affiliations

Adolescents' self-identified peer group affiliation is associated with health risk behaviors such as involvement in substance use and violence. This prospective study examined the association between peer group self-identification during high school and psychosocial functioning five years later among a sample of continuation high school students (i.e., students attending alternative public schools). Participants were recruited as part of Project TND, a substance use prevention project conducted in 21 school districts from a five-county region of Southern California. The sample included 532 students, ranging in age from 19 to 24 years most of whom were male (57%) and half were Latino (50%). Participants named the peer group which they felt "most a part of." Responses were collapsed into four general group categories: high-risk youth, jocks-hotshots, regulars, and others. Results indicated that students who self-identified with high-risk peer groups while in continuation high school were most likely to report involvement in drug use and violence during young adulthood, and they were significantly less likely to have graduated from high school or secure stable employment. Sussman, S., Unger, J.B. and Dent, C.W. Peer Group Self-Identification among Alternative High School Youth: A Predictor of Their Psychosocial Functioning Five Years Later. International Journal of Clinical and Health Psychology, 4, pp. 9-25, 2004.

Early Screening is Effective for Externalizing Problems

Accurate early screening is a prerequisite for indicated interventions intended to prevent development of externalizing disorders and delinquent behaviors. Using data from the Fast Track longitudinal sample of 396 children from high-risk environments, assumptions about base rates were varied to examine effects of multiple-time-point and multiple-rater screening procedures, and considered the practical import of various levels of screening accuracy in terms of true and false positive rates and their potential costs and benefits. The results indicate that 1st grade single- and multiple-rater screening models effectively predicted externalizing behavior and delinquent outcomes in 4th and 5th grades. Thus while additional research is needed to determine true costs and benefits of early screening, early screening is justified. Hill, L.G., Lochman, J.E., Coie, J.D. and Greenberg, M.T. Effectiveness of Early Screening for Externalizing Problems: Issues of Screening Accuracy and Utility. Journal of Consulting and Clinical Psychology, 72(5), pp. 809-820, 2004.

Drug Use may be Mediated through Low Hostile Anger Control

The relationships among selected predictors of violence, including victimization, low conflict management efficacy, hostile anger and drug use were examined using data on 8th-, 10th-, and 12th-grade adolescents. The secondary analysis used a population-based, cross-sectional survey of health behaviors (N = 3,922). For each grade cohort, it was hypothesized that victimization and low conflict management efficacy would predict low hostile anger control, which would predict gateway drug use, and the subsequent development of hard drug use and violence. Overall model fit and the magnitude of specific paths were expected to increase across grades. Using structural equation modeling (SEM), results indicated acceptable model fit for 8th-grade (CFI = .95), 10th-grade (CFI = .93) and 12th-grade (CFI = .94) cohorts. Results suggest that the influence of relational victimization and conflict management efficacy on hard drug use may be mediated through low hostile anger control and gateway drug use. Weiner, M.D., Pentz, M.A., Skara, S.N., Li, C., Chou, C.P. and Dwyer, J.H. Relationship of Substance Use and Associated Predictors of Violence in Early, Middle, and Late Adolescence. Journal of Child & Adolescent Substance Abuse, 13(4), pp. 97-117, 2004.

Using Virtual Reality to Assess Adolescents' Social Competency

Over the decades many interventions have been aimed at improving adolescents' social competency skills in order to affect outcomes such as interpersonal violence and substance abuse. However, assessment of these skills has been limited to self-ratings or external ratings by teachers and parents and archival records. Responsive virtual human (RVH) technology is a rapidly advancing method for assessing technical and social competency skills. By allowing individuals to engage in seemingly real verbal discourse with virtual characters they are afforded a more realistic social encounter than less interactive paper or computer-based assessments. This study examined the psychometric properties of performance measures for three novel, interactive virtual reality vignette exercises developed to assess social competency skills of at-risk adolescents. Data for 18 performance measures were collected from 117 African-American male 15-17 year olds based on their interactions with a provocative virtual teenage character. Twelve of the 18 performance measures loaded on two factors corresponding to emotional control and interpersonal communication skills, providing support for their factorial validity. Overall, the study findings suggest that the virtual reality vignette exercises may represent a promising approach for assessing adolescents' social competency skills in the context of prevention research. Paschall, M.J., Fishbein, D.H., Hubal, R.C. and Eldreth, D. Psychometric Properties of Virtual Reality Vignette Performance Measures: A Novel Approach for Assessing Adolescents' Social Competency Skills. Health Education Research, 1-10, Advance Access published July 14, 2004.

Alcohol and Marijuana Use Among College Students

Previous research has shown that the recent tightening of college alcohol policies has reduced college students' drinking. Over the period in which these stricter alcohol policies have been put in place, marijuana use among college students has increased. This raises the question of whether current policies aimed at reducing alcohol consumption are inadvertently encouraging marijuana use. This paper addressed this question by investigating the relationship between the demands for alcohol and marijuana for college students using data from the 1993, 1997, and 1999 waves of the Harvard School of Public Health's College Alcohol Study (CAS). Researchers found that alcohol and marijuana are economic complements and that policies that increase the full price of alcohol are associated with decreased participation in marijuana use. Williams, J., Pacula, R.L., Chaloupka, F.J., and Wechsler, H. Alcohol and Marijuana Use Among College Students: Economic Complements or Substitutes? Health Economics, 13(9), pp. 825-843, 2004.