Earlier Marijuana Use and Later Problem Behavior in Colombian Youths

Earlier Marijuana Use and Later Problem Behavior in Colombian Youths JUDITH S. BROOK, ED.D., DAVID W. BROOK, M.D., ZOHN ROSEN, M.S., AND CAITILIN R. RABBITT, M.A.

ABSTRACT Objective: The study examined the relationship between earlier adolescent marijuana use and later adolescent behavioral problems. Method: A community-based sample of Colombian adolescents was interviewed in 1995–1996 and 1997–1998. The time 2 (T2) sample consisted of 1,151 males and 1,075 females. The psychosocial measures assessed adolescent problem behavior, the peer and sibling social network, and ecological/environmental stress and cultural domains. Logistic regression analyses included controls on demographic and time 1 (T1) dependent measures. Results: The findings suggest that T1 adolescent marijuana use was associated with increased risks for T2 adolescent difficulty at work or school, violent experiences, peer marijuana use, and sibling marijuana problems. Conclusions: This study provides important evidence in this cohort of the specific relationship between T1 adolescent marijuana use and T2 adolescent problem behavior in a society in which drug use, crime, violence, and low educational attainment are pervasive. Similar findings have been shown in previous research with U.S. adolescents. The findings suggest that early adolescent marijuana use is associated with an increase in problem behavior during later adolescence. J. Am. Acad. Child Adolesc. Psychiatry, 2003, 42(4):485–492. Key Words: adolescent marijuana use, Colombia, problem behaviors.

Previous research with U.S. subjects has indicated that marijuana use in early adolescence may be associated with such problems as unemployment, depression, drug and health problems, and difficulty at work or school (Brook et al. 1999a, 2000; Johnson and Kaplan, 1990). Some research has indicated that marijuana use is related to decreased academic achievement and increased delinquent activity (Brook et al. 1999a; Brown et al., 1996), although not all studies have confirmed these findings (White, 1991). This study extends earlier research on the consequences of early adolescent marijuana use within a sample of Colombian youths in a social context in which drug use, violence, and Accepted November 12, 2002. From the Department of Community and Preventive Medicine, Mount Sinai School of Medicine, New York. This research was supported by Research Scientist Award DA 00244-8 and Research Grant DA 10348-05 from NIDA, NIH, to J.S.B. The authors gratefully acknowledge Drs. Mario De La Rosa and Yvan Montoya, who were instrumental in obtaining the sample, and two anonymous reviewers for their thoughtful and helpful comments. Correspondence to Judith S. Brook, Ed.D., Department of Community and Preventive Medicine, Box 1044A, Mount Sinai School of Medicine, One Gustave L. Levy Place, New York, NY 10029-6574. 0890-8567/03/4204–0485䉷2003 by the American Academy of Child and Adolescent Psychiatry. DOI: 10.1097/01.CHI.0000037050.04952.49

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low educational attainment are prevalent (Druzan, 1994; Duke and Gross, 1994; Terris, 1998). Attitudinal measures hypothesized to have a significant relationship with earlier adolescent marijuana use, including perceived drug risk, tolerance of deviance, and school achievement, are tested within the problem attitude and behavior domain. Despite increases in educational attainment within the Colombian population within the past few decades, low educational attainment is still common and, overall, only four fifths of Colombian children attend school at any point in time (U.S. Department of Justice, 1997). Therefore, educational attainment and school attendance indicators are also tested in the problem attitude and behavior domain. The peer and sibling social network domain measures peer marijuana use and deviance and sibling marijuana problems. Previous research suggests that (1) peers influence adolescent behavior (Dishion et al., 1994; Jessor et al., 1980), (2) adolescents’ own predispositions may lead them to select deviant peers (Dinges and Oetting, 1994), and (3) there may be a reciprocal relationship between adolescent drug use and deviant peers (Kandel, 1996). The psychosocial variables within the problem attitude and behavior domain and the peer and sibling social network domains were hypothesized to have similar rela485

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tionships to early adolescent marijuana use as the results obtained in research findings with U.S. adolescents. The Colombian sample provides an important opportunity to test these relationships. Despite almost a half-century of continuous democratic government, contemporary Colombia is characterized by violent political conflicts, one of the highest homicide rates in the world, and readily available drugs, including marijuana, cocaine, and basuco, a coca leaf derivative (Colombian Ministry of Justice, 1995; Deas and Daza, 1995; Druzan, 1994; Terris, 1998; U.S. Department of Justice, 1997). U.S. research indicates that ecological conditions including drug availability and neighborhood violence, as well as an unsupportive school environment, are linked with increased adolescent drug use (Brook et al., 1997; Duke and Gross, 1994). This study includes multiple measures of contextual violence and environmental stress, such as drug availability, neighborhood victimization, and work stress or a poor school environment. Several variables address Colombian cultural norms, including gender roles. Colombian society observes norms of male machismo, or dominance, and female marianismo, or moral and sexual purity; machismo has been associated with drug use (Lara-Cantu, 1989). Previous research has indicated that a close relationship between marijuana-using children and their parents can mitigate the risks for children of later problem behaviors (Brook et al., 1990, 1993). “Familism,” or prioritizing families over individual interests, is characteristic of Colombian culture (Ingoldsby, 1991), so a familism measure is included within the cultural domain. Colombia has a long tradition of Roman Catholicism. While the Church relinquished control over social institutions including schools and civil marriage in 1973, 95% of the Colombian population still professes to be Roman Catholic (U.S. Department of Justice, 1997). Because low religious service attendance has been associated with adolescent drug use (Brook et al., 1999a), we include a measure of church attendance. Investigation of the relationship between earlier marijuana use and later life problems requires conducting prospective longitudinal research with a communitybased sample. Factors that may account for the association between early marijuana use and later life problems, such as parental occupation, adolescent age, gender, or ethnicity, or early adolescent problem attitudes or behaviors, must be assessed and controlled statistically. Our review of the literature indicates a dearth of research into 486

the association between marijuana use and later problem behaviors and attitudes meeting all of these methodological criteria. Consequently, we used data from a community-based prospective longitudinal study in Colombia to examine the relationships between T1 adolescent marijuana use and T2 adolescent problem behaviors. Statistical controls include age, gender, ethnicity, and parental occupation, and the T1 level of the T2 dependent variable. METHOD Sample Procedure Interviews were conducted privately within the adolescents’ homes at both T1 and T2 after the adolescents and their mothers had signed consent forms (see Brook et al., 1999b, for further information). The Institutional Review Board at the Mount Sinai School of Medicine approved all survey protocols, and each interview took approximately 2 hours. The interviewers, all college graduates or above, were trained for 8 hours and individually monitored by supervisors on a regular basis. They followed a standardized protocol, which was reviewed with all interviewers, both before and during its administration; 70% of the completed questionnaires were reviewed for accuracy by supervisors, who also reviewed the questionnaires together with the interviewers. Although the interviews were similar at T1 and T2, different interviewers were used at T1 and T2. The interviewers read the questions aloud to the adolescents as they followed along in their copies of the questionnaires. All subjects understood the questions. Participants were instructed that their answers were strictly confidential and that interview schedules were identified only with a code number. The adolescents were given hats or T-shirts as incentives to participate. The adolescent subjects at T2 were interviewed in the same order as at T1, maintaining approximately a 2-year interval between interviews. This community sample of adolescents was drawn from three Colombian cities: Barranquilla, Medellín, and Bogotá. Bogotá, the Colombian capital, has large concentrations of young people with varying urban experiences. Medellín is the second Colombian city by size and population, and a commercial and industrial center. Barranquilla is located on the coast and manifests a costeño (Caribbean-like) culture. Households with at least one child between the ages of 12 and 17 were qualified for this study. Within each city a sample was obtained from census data. We selected households that met our criteria, and from that list we randomly selected the subjects. Interviewers were sent to addresses via a process of random assignment. Only qualified individuals within households were considered for the study. In cases in which more than one adolescent in the household was qualified for the study, subjects were selected randomly using prepared tables. The time 1 (T1) initial sample included 2,837 Colombian adolescents, and the time 2 (T2) sample comprised 2,226 respondents, or 78% of the T1 sample. None of the demographic factors differentiated the T2 sample from the T1 sample, including age, sex, ethnicity, and socioeconomic status (SES). The T1 subjects who could not be interviewed at T2 had higher rates of unconventionality, sibling and peer drug use, environmental stress, and contextual violence. Details regarding the demographics for this sample are presented in Table 1. Measures Marijuana Use. The independent variable, T1 marijuana use, was based on a 6-point categorical scale of past and present marijuana use,

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TABLE 1 T1 and T2 Demographic Data for the Longitudinal Sample (N = 2,226) Gender, % Male Female Ethnicity, % Mestizo (Spanish, Indian, African-Columbian) Spanish Other (African, Asian, Indian, other European)

52 48 57 32 11

Mean age (SD) Living with 2 parents, % Attending school, % Mean education level Father’s occupation, % (n) Never employed, unskilled, semiskilled, homemaker Skilled, clerical, semiprofessional, military Professional Father’s education, % (n) None–9th grade 10th grade–university graduate Business/technical/graduate school

coded from “Not at all” to “Every day.” Marijuana use, as distinguished from marijuana abuse or dependence (Kolansky and Moore, 1971), was measured with a standard self-report measure whose predictive validity is supported by previous analyses (Brook et al., 1989, 1999a). DSM-IV criteria were not used to assess cannabis abuse and dependence. At T1, adolescent marijuana use was assessed and is presented as the percentage of participants at each level of use: never, 60%; once or twice, 23%; 3 to 11 times, 8%; monthly basis, 3%; once a week, 1%; several times a week or more, 5%. For the analysis, T1 marijuana use was dichotomized at marijuana used “Once a month or more,” for comparability with previous research (Brook et al., 1999a). At T2, adolescent marijuana use was assessed again and is also presented as the percentage of participants at each level of use: never, 53%; once or twice, 22%; 3 to 11 times, 11%; monthly, 5%; once a week, 1%; several times a week to daily use or more, 8%. Covariates. Covariates included the subjects’ age, gender, ethnicity, the father’s occupational status (as a proxy for SES), and the T2 psychosocial measures obtained at T1, as noted below. Demographic controls were included because previous research has shown that these factors are related to marijuana use in adolescence and to several of the psychosocial measures. We examined the relationship between marijuana use at T1 and the T2 psychosocial measures obtained at T1, as well as the demographic factors. Both age and gender were significantly related to marijuana use at T1 (r = 0.26, p < .001; t2,050 = 8.22 favoring males, p < .001, respectively). The other demographic covariates (i.e., ethnicity and SES) were added to make this study consistent with other research examining the relationship between marijuana use and psychosocial factors. Also, the correlations between the T2 psychosocial measures and the parallel psychosocial measures assessed at T1 were all statistically significant. Consequently, we controlled for the initial (T1) value of the psychosocial variables to clearly assess the association of T1 marijuana use on the T2 outcomes. Behavioral Measures. The psychosocial domains included problem attitudes and behaviors, the peer and sibling social network, ecological/environmental stress factors, and cultural norms. Except for variables based on either yes/no questions or ordinal scales, the measures

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Time 1

Time 2

15.2 (1.66) 65 84 7th grade

17.2 (1.88) 66 71 8th grade

59 (1,307) 34 (750) 7 (169)

61 (1,349) 31 (693) 8 (184)

74 (1,645) 24 (539) 2 (42)

73 (1,620) 25 (569) 2 (37)

were multiquestion scales that have demonstrated interitem reliability and predictive validity in previous research with U.S. white, AfricanAmerican, and Puerto Rican subjects (Bem, 1974; Brook et al., 1999a; French et al., 1982; Gold, 1966; Jessor et al., 1968; Johnston et al., 1987; H.B. Kaplan, personal communication, April 22, 1993; Newcomb, 1988, 1995; P. O’Malley, personal communication, August 17, 1994; Rodriguez, 1989; Rogler and Cooney, 1984; Smith and Fogg, 1979). Six researchers fluent in English and Colombian Spanish translated the items from English into Spanish, and questions were revised in instances of disagreement regarding idiomatic consistency. The questions were also back-translated to ensure face validity. Two pilot studies were conducted to ensure comparability between the psychometric properties of the translated scales and those of scales used in U.S. research. With one exception, the dependent measures were dichotomized at the mean plus 1 SD. Educational attainment was dichotomized at the mean minus 1 SD, to identify the low educational attainment group. A list of the psychosocial measures, including the Cronbach α values, sample items, and scale sources, is included in Table 2. Data Analysis The research methodology in this study used logistic regression analyses. In logistic regression analyses with the T2 adolescent psychosocial variables serving as dependent measures, 14% of the interaction terms between T1 adolescent marijuana use and the demographic covariates (age, gender, ethnicity, and SES) were significant. We ran two series of logistic regression analyses to examine T1 marijuana use by the T2 psychosocial measures, first controlling for T1 age, gender, ethnicity, and SES, and then also controlling for the T2 measure as assessed at T1. RESULTS

As shown in Table 3, the results of the logistic regression analyses reveal a consistent pattern: earlier adoles487

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TABLE 2 Psychosocial Measures: Sources, α Values, Number of Items, and Sample Items Scale Source

α

No. of Items

Sample

Jessor et al., 1968

.82

7

Delinquency Rebelliousness

Gold, 1966 Smith and Fogg, 1979

.75 .55

5 7

Drug risk

Johnston et al., 1987

.83

2

O’Malley, personal communication, 1994 Newcomb, 1988, 1995

.87

7

.71

3

How wrong do you think it is to fake an excuse note from home for school? How often have you cheated on tests or work? Sometimes you enjoy seeing how much you can get away with. How much do you think people risk harming themselves physically or in other ways if they sometimes use cocaine or basuco? How often have you had trouble at school or on the job because of your use of alcohol or drugs? How many times in the last 6 months were you high drunk, or stoned while at school or work?

Original Original Kaplan, personal communication, 1993

— — .49

1 1 4

Are you still attending school, either part- or full-time? What was the last year of school you were in? How often do (did) you miss classes?

Gold, 1966

.77

5

Peer marijuana use

Original

—

1

Sister marijuana problems

Original

—

1

Brother marijuana problems

Original

—

1

How many of your friends have taken something from a desk or locker without asking? How many of your friends use marijuana more than once a month on average? Have any of your biological sisters, including halfsisters, had a problem with marijuana? Have any of your biological brothers, including halfbrothers, had a problem with marijuana?

Chavez et al., 1994 Rodriguez, 1989

.75 .96

5 5

French et al., 1982

.96

7

Johnston et al., 1987 Original Original

.79 .87 .86

2 4 5

Bem, 1974 Bem, 1974 Rodriguez, 1989

.69 .73 .63

10 10 10

Original

—

1

Domains Adolescent problem behaviors Tolerance of deviance

Drug/alcohol problems with school/work/health Incapacitated at school or work from alcohol, marijuana, or other drugs School outcome School attendance Educational attainment Perceived school achievement Peer and sibling Peer deviance

Environment Violence toward subject Victimization in neighborhood Work stress Drug availability School environment Satisfaction with school Cultural Masculinitya Femininitya Familismb Religious attendance

How often has someone cut you with a knife? In your neighborhood how safe do you feel from street fights about drugs? Do you find it difficult to meet all the demands placed on you at work? How difficult is it to get marijuana? Students try to learn as much as they can. Do you think the things you learn are important and useful? How well does the word “competitive” describe you? How well does the word “gentle” describe you? When someone has serious problems, only relatives can help. How often do you go to church or attend religious services?

a The masculinity scale captures several aspects of the Colombian cultural characteristic of machismo (male strength and assertiveness), while the femininity scale acts as a measure of marianismo (female virtue, gentleness, and willingness to sacrifice), the Colombian cultural norm for women. b Familism is a Colombian cultural value that places the value of the family above the individual.

cent marijuana use is associated with multiple problems later in adolescence. Earlier adolescent marijuana use was associated with increased levels of all of the T2 problem attitude and behavior measures, despite control on age, gender, ethnicity, SES, and the T2 measure assessed at T1. Earlier adolescent marijuana use was associated with 488

increased levels of later low perceived drug risk (odds ratio [OR] = 1.677, 95% confidence interval [CI] 1.191–2.362, p < .01), high tolerance of deviance (OR = 2.126, 95% CI 1.353–3.341, p < .01), and rebelliousness (OR = 2.119, 95% CI 1.485–3.024, p < .0001). Significantly, earlier adolescent marijuana use, with demo-

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TABLE 3 Logistic Regression Analyses: Earlier Adolescent Marijuana Use (T1) and Later Problem Outcomes (T2) (N = 2,226) T2 Problem Outcomes (Dependent Measures) I. Problem attitude and behavior domain Low perceived drug risk Tolerance of deviance Rebelliousness Drug problems Delinquency Incapacitated at school or work Poor school achievement Less frequent school attendance Low educational attainment II. Peer and sibling social network domain Peer deviance Peer marijuana use Marijuana problems—brother Marijuana problems—sister III. Ecological/environment stress domain Violence directed at subject Neighborhood victimization Work stress Drug availability Poor school environment Low school satisfaction IV. Cultural domain Femininity Masculinity Familism Religious attendance

OR

95% CIa

OR

95% CIb

1.737** 2.157***c 2.447† c 10.717† c 4.053† c 11.435† c 1.969** 3.527† c 5.009† c

1.236–2.442 1.383–3.364 1.730–3.459 7.357–15.613 2.931–5.606 7.601–17.201 1.204–3.219 2.559–4.862 3.569–7.030

1.677** 2.126** 2.119† c 5.958† c 3.134† c 6.494† c 2.031** 2.130† c 2.934† c

1.191–2.362 1.353–3.341 1.485–3.024 3.840–9.243 2.232–4.401 3.909–10.789 1.241–3.323 1.503–3.019 1.841–4.677

2.196† c 5.334† c 5.259† c 7.760† c

1.593–3.027 3.840–7.408 3.382–8.178 3.696–16.290

1.916***c 2.644† c 2.860† c 4.458***c

1.380–2.660 1.859–3.759 1.701–4.810 1.906–10.431

4.238† c NS NS 1.724*** c 1.573* 1.639*

2.941–6.108

2.153–4.599

1.271–2.339 1.035–2.393 1.123–2.392

3.147† c NS NS 1.430* 1.639* 1.652**

1.044–1.959 1.080–2.486 1.135–2.405

0.271–0.957 0.389–0.880

NS NS NS 0.624*

0.410–0.949

NS NS 0.509* 0.585*

Note: OR = odds ratio; CI = confidence interval; NS = not significant. a Logistic regression analyses controlled for T1 age, gender, ethnicity, and socioeconomic status. b Logistic regression analyses controlled for T1 age, gender, ethnicity, socioeconomic status, and the T2 dependent variable assessed at T1. c Test is significant with corrected Bonferroni α level. * p < .05; ** p < .01; *** p < .001; † p < .0001.

graphic and T1 psychosocial measure controls, was observed to be associated with a large increase in all of the other problem behaviors, including drug problems (OR = 5.958, 95% CI 3.840–9.243, p < .0001), delinquency (OR = 3.134, 95% CI 2.232–4.401, p < .0001), and drug- or alcohol-related incapacitation at work or school (OR = 6.494, 95% CI 3.909–10.789, p < .0001). Earlier adolescent marijuana use, with the T1 control, was associated with all of the later adverse adolescent school measures. Earlier adolescent marijuana use predicted poor school achievement (OR = 2.031, 95% CI 1.241–3.323, p < .01), less frequent school attendance (OR = 2.130, 95% CI 1.503–3.019, p < .0001), and low educational attainment (2.934, 95% CI 1.841–4.677, p < .0001). Adolescent marijuana use also has a clear relationship to problem behaviors within the adolescents’ social netJ . A M . A C A D . C H I L D A D O L E S C . P S YC H I AT RY, 4 2 : 4 , A P R I L 2 0 0 3

works. Earlier adolescent marijuana use was associated with later increased sibling marijuana use problems for both brothers (OR = 2.860, 95% CI 1.701–4.810, p < .0001) and sisters (OR = 4.458, 95% CI 1.906–10.431, p < .001). Earlier adolescent marijuana use was also associated with later peer marijuana use (OR = 2.644, 95% CI 1.859–3.759, p < .0001) and peer deviance (OR = 1.916, 95% CI 1.380–2.660, p < .001). Relatively fewer ecological/environmental stress or cultural domain measures were significantly related to earlier adolescent marijuana use, indicating a weaker relationship to marijuana use. Within the ecological/environmental stress domain, earlier adolescent marijuana use was only associated with later violence directed at the subject (OR = 3.147, 95% CI 2.153–4.599, p. < .0001) and drug availability (OR = 1.430, 95% CI 1.044–1.959, p < .05). 489

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Indicators of work stress and neighborhood victimization were not significant in any regression models. Earlier adolescent marijuana use was, however, associated with increased levels of a perceived poor school environment (OR = 1.639, 95% CI 1.080–2.486, p < .05) and low school satisfaction (OR = 1.652, 95% CI 1.135–2.405, p < .01). Among the cultural variables, logistic regression models based on the entire sample indicated that earlier adolescent marijuana use was not significantly associated with measures of either femininity or masculinity. The familism measure had a significant inverse relationship to earlier adolescent marijuana use (OR = 0.509, 95% CI 0.271–0.957, p < .05). However, this association was not sustained with the introduction of the T1 controls. Earlier adolescent marijuana use also had an inverse relationship with later religious attendance (OR = 0.624, 95% CI 0.410–0.949, p < .05). As a cautionary note, the Bonferroni test was computed by correcting for the number of variables within each domain, and only those variables significant at the corrected level are labeled as such in Table 3. For example, the p values for the problem attitude and behavior tests were adjusted to correct for the nine tests performed within that domain (i.e., p < .0056), and findings significant at that level are marked as such in Table 3. It should be noted that with the exception of the cultural domain, most of the findings remained intact, even after adjusting the significance level with a Bonferroni correction. However, the Bonferroni test is not strictly appropriate for adjusting the significance of odds ratios and is considered overly conservative when applied in this context. Consequently, our results are presented both in a standard format and with multiple-test corrections applied. DISCUSSION

This study supports and extends previous research in a number of significant ways. First, the findings reveal consistent relationships between early marijuana use and later life functions. Early marijuana use was associated not only with specific drug-related outcomes, but also with more general problems including rebelliousness, poor school performance, and exposure to drugs, violence, and drug-using or delinquent peers. Marijuana use may presage difficulties in both the intrapersonal and interpersonal realms. Second, the longitudinal research design enhances the predictive value of the findings. Third, the study sample comprised a large and diverse popula490

tion of adolescents living in Colombia, where violence is endemic and drugs are readily available. Thus an association between earlier marijuana use and later problem behaviors is maintained even in a setting where drug use and violence may be primarily attributable to relatively extraneous factors, such as drug cartels or drug “turf wars,” rather than the emotional or social factors frequently associated with adolescent drug use in U.S. research (Brook et al., 1999a; Duncan et al., 1998). Fourth, our T1 psychosocial measure controls allow examination of increments in problem behaviors from T1 to T2 as specifically related to marijuana use. Fifth, the results indicate that marijuana users may select environments favorable to the development of problem behaviors. Several mechanisms may explain the association found by this study between earlier marijuana use and later difficulty in a number of important life areas. The relationship between earlier marijuana use and later problem behavior could be due to the psychopharmacological or toxic effects of marijuana on brain functioning or metabolism. For instance, the neurotransmitter dopamine has been implicated in the positive reinforcing actions of tetrahydrocannabinol, the major psychoactive component of marijuana (Tanda et al., 1997). In addition, marijuana use may be related to impaired cognitive functions such as attention, comprehension, or planning (Tinklenberg and Darley, 1975). A second mechanism may be via the “amotivational syndrome,” a behavioral pattern characterized by apathy and impaired life functioning (Koop, 1982), seen in the low levels of motivation for academic achievement and educational attainment found among some marijuana users (Brook et al., 1989, 1999a). Also, marijuana use may result in difficulty in the attachment relationship between parent and child (Brook et al., 1989), while difficulty in the parent–child relationship predicts later problem behavior (Brook et al., 1998). There may be a common, earlier risk/vulnerability for marijuana use and problem behaviors, consisting of genetic vulnerability, temperamental factors/behavioral disinhibition, or parental substance use disorders (Glantz et al., 1999). The data indicating that earlier marijuana use was related to delinquency and tolerance of deviance, consistent with findings of U.S. studies (Brook et al., 1999a), suggest an inverse relationship between marijuana use and adolescent socialization to adult social roles. These empirical findings, within a developmental model focusing on the influences of domains of socialization (Brook et al., 1988), suggests that marijuana users may have a predilection J . A M . A C A D . C H I L D A D O L E S C . P S YC H I AT RY, 4 2 : 4 , A P R I L 2 0 0 3

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toward participation in social environments that further reinforce any existing problem attitudes or behaviors. In line with previous research (e.g., Kandel, 1996), early marijuana use precedes susceptibility to the influences of delinquent peers and marijuana-using peers, despite control on earlier delinquency and peer marijuana use levels. That is, marijuana use is related to selecting friends who use marijuana, while associating with marijuana-using friends is related to later marijuana use. Early adolescent marijuana use preceded later health problems or depression, and later drug- or alcohol-related difficulty at school or work. Adult drug use, including marijuana use, has been related to work problems including unemployment and low job satisfaction (Stein et al., 1993). Besides associating with deviant peers, adolescents who use marijuana were more likely to be the victims of violent behavior and to report ready drug availability. Overall, marijuana users’ predisposition for risky social environments may further reinforce any other existing proclivities for delinquent or otherwise dangerous activities. Moreover, the thesis that early adolescent marijuana use may be associated with a predilection for risky environments receives indirect support from findings suggesting less attachment to conventional institutions among early marijuana users. Early adolescent marijuana users showed a decreased T2 propensity to attend church, a finding consistent with research conducted within the United States. (Brook et al., 1999a). Early adolescent marijuana users were also less prone to remain in school or to report satisfaction with their school environments. These findings may relate to U.S. research indicating that students who did not use marijuana were more likely to state that marijuana use within the school contributed to socially exclusionary cliques, school violence, and transforming schools into “drug connections” (Lamanna, 1981). Thus adolescents who use marijuana may be exposed to different environments although they attend the same school. Although adolescent marijuana users may be predisposed to select drug-prone environments, youths at risk for early cannabis use, abuse, or dependence may also have a genetic or temperamental predisposition for behavioral disinhibition and risk-taking behavior early in development (Tarter, 1988). Furthermore, there is evidence that comorbid disorders such as attention-deficit/hyperactivity disorder, depressive and anxiety disorders (notably, posttraumatic stress disorder), and conduct disorders may also pose an early developmental proclivity for substance use disorders in adolescents (Aytaclar et al., 1999; Brown et al., 1996). J . A M . A C A D . C H I L D A D O L E S C . P S YC H I AT RY, 4 2 : 4 , A P R I L 2 0 0 3

Although we do not have a DSM-IV measure of conduct disorder, many of the problem behaviors reported may be interpreted as symptoms of current conduct disorder or risks for later conduct disorder. For example, tolerance of deviance, drug problems, and delinquency all reflect violations of social norms, a factor common to conduct disorder. Similarly, less frequent school attendance may reflect truancy, another example of deviating from accepted norms. Such an interpretation together with our data implies that these earlier symptoms of conduct disorder do not account for the relation of earlier marijuana use and later problem behavior. Control on the T1 measures of these symptoms or risks still preserved the significant relations between earlier marijuana use and the later problem behaviors which could also be interpreted as symptoms of conduct disorder. Limitations

Several caveats might be mentioned. First, caution is always warranted in making causal interpretations based on correlational data. Nevertheless, controlling for the T1 levels of the dependent measures in examination of the relationship between earlier adolescent marijuana use and later T2 outcomes diminishes the importance of any unknown variables. Second, cigarette smoking may account for the more potent effects of marijuana use on increased adverse problem behaviors. To the extent that cigarette smoking contributes to the T2 measures, the inclusion of problem behavior at T1 in the analysis serves as a partial control. Third, subjects lost to attrition were more unconventional, which may have altered the results. If these subjects had been included, our findings might have been even stronger. Clinical Implications

Prevention and treatment programs should consider increasing adolescents’ awareness of the risks associated with marijuana use, for both the short term and the long term. Although translational research needs to be performed to confirm our results, our findings suggest that to the extent that marijuana use adversely affects adolescent behavior, a decrease in marijuana use may decrease problem behaviors. Our findings also indicate that marijuana use may predispose adolescents to select environments that reinforce the adverse effects of any existing risk factors. Consequently, health care programs might also focus on teaching adolescents who are at risk for using marijuana to mitigate the adverse impacts of marijuana 491

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