Effects of risk perception of marijuana use on marijuana use and intentions to use among adolescents in Bogotá, Colombia

Drug and Alcohol Dependence 109 (2010) 65–72

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Effects of risk perception of marijuana use on marijuana use and intentions to use among adolescents in Bogotá, Colombia Catalina Lopez-Quintero ∗ , Yehuda Neumark Braun School of Public Health & Community Medicine, Hebrew University-Hadassah, Jerusalem 91120, Israel

a r t i c l e

i n f o

Article history: Received 22 March 2009 Received in revised form 13 November 2009 Accepted 1 December 2009 Available online 13 January 2010 Keywords: Perceived risk Adolescents Marijuana Intentions to use marijuana

a b s t r a c t Background: Perceived risk is a key concept of behavioral theories used to predict substance use among youth and a core component of drug use prevention interventions. The present study aimed to (1) assess degrees of risk perception of regular marijuana use, (2) identify factors associated with risk perception, and (3) explore the associations between perceived risk and marijuana use and intentions to use marijuana among school-attending adolescents in Bogotá, Colombia. Methods: Data from 2079 standardized questionnaires administered in 23 schools were analyzed in this study. Schools were selected in a multi-stage probability cluster sample to reflect the socio-economic characteristics of Bogotá’s student population. Results: Just over 11% of participants perceived regular marijuana use to be a low risk behavior. Older age (>16 years) (adjusted odds ratio = 2.9; 95% confidence interval = 1.4–6.0) and low level of knowledge regarding the physical and psychological harms of illegal drugs (AOR = 2.9; 95%CI = 2.0–4.3) were the strongest predictors of low risk perception, Low perceived risk was also significantly associated with ever having used marijuana (AOR = 2.5; 95%CI = 1.7–3.7), monthly marijuana use among ever marijuana users (AOR = 2.7; 95%CI = 1.4–5.0), and a positive intention to use marijuana within the next 12 months among non-users (AOR = 2.1; 95%CI = 1.4–3.5). Conclusions: Consistent with previous findings, perceiving regular marijuana use as a risky behavior functions as a protective factor against the intention to use, use and occasional use of marijuana. Incorporation of this message into drug use prevention activities for non-users and early-stage users may enhance their effectiveness. © 2009 Elsevier Ireland Ltd. All rights reserved.

1. Introduction Risk perception, defined as the subjective judgment that people make about the characteristics and severity of a risk (Kirch, 2008), is a key concept of diverse behavioral theories that have been used to predict substance use among youth (Ajzen, 2001; Ajzen and Fishbein, 1980; Bandura, 1986; Janz and Becker, 1984; Weinstein, 1993). Specifically, research based on these theories emphasizes the significant role played by this construct in influencing the individual’s intention to use marijuana and its use (Ajzen et al., 1982; Conner and McMillan, 1999; Kam et al., 2009; Olds et al., 2005). Numerous operational definitions of perceived risk of drug use have been suggested according to the areas of influence com-

∗ Corresponding author at: Braun School of Public Health & Community Medicine, Hebrew University-Hadassah, P.O.B. 12272, Jerusalem 91120, Israel. Tel.: +972 2 6439103; fax: +972 2 6431086. E-mail address: [email protected] (C. Lopez-Quintero). 0376-8716/$ – see front matter © 2009 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.drugalcdep.2009.12.011

monly affected (personal, social, or legal consequences) and to characteristics of the potential risk (Danseco et al., 1999). Regardless of definition employed, a relationship between perceived risk and substance use has been frequently shown (Bachman et al., 1998; Gerrard et al., 1996; Johnston et al., 2005; Kilmer et al., 2007), although the complexity of this relationship in terms of directionality and temporality precludes straightforward interpretations. Findings from the Monitoring the Future (MTF) study of adolescents in the US over the last 30 years reveal a consistent inverse association between perceived risk and drug use. Youth who perceive a greater risk of marijuana use are less likely to report having used the drug (Bachman et al., 1998; Johnston et al., 2005). Similar findings have been reported among young adults entering college in the US (Kilmer et al., 2007). Other studies, however, have reported a positive relationship whereby increased perception of drug use-related risk is associated with a higher prevalence of use (Gerrard et al., 1996; Sjöberg, 1998). These somewhat counterintuitive findings have been explained by behavior normalization (i.e., overestimating other people’s risk behaviors) and by minimiz-

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ing the influence of health and safety concerns on the behaviors (Gerrard et al., 1996; Halpern-Felsher et al., 2004; Sjöberg, 1998). According to the World Mental Health Survey Initiative, Colombia exhibited the highest adult prevalence of marijuana (10.8%) and cocaine (4.0%) use among less-developed countries (Degenhardt et al., 2008). Moreover, results from a school-based study of nine South-American countries (Inter-American Drug Abuse Control Commission, 2004) indicate that Colombian youth exhibit high rates of legal and illegal drug use compared with the majority of the countries surveyed. This situation has been linked to the underlying high levels of environmental stress stemming from the ongoing internal civilian conflict that plagues Colombia, marked social inequalities, and high levels of corruption and violence, among other macro-level factors (Brook et al., 1998, 2003; Siqueira and Brook, 2003). As a former leading marijuana producer and the world’s largest cocaine producer (United Nations Office for Drug Control and Crime Prevention, 2008), most of the attention to the country’s drug problem has been focused on international trafficking, and much less on local use and its ramifications. In view of the high prevalence of marijuana use among Colombian adolescents, the centrality of perceived risk in the development of prevention strategies and its significance as an epidemiological indicator of drug use, the present study of a representative sample of school-attending adolescents in Bogotá, Colombia aimed to (1) assess degrees of risk perception of regular marijuana use, (2) identify factors associated with low risk perception of regular marijuana use, and (3) explore the associations between low perceived risk and marijuana use, monthly marijuana use among study participants who ever used marijuana, and intentions to use marijuana in the next 12 months among respondents who never used marijuana. 2. Methods 2.1. Study population A school-based study was conducted in 2006 in 23 schools (66 classes) in Bogotá, Colombia. The multi-stage cluster sample was designed to reflect the socio-economic characteristics of adolescents registered in Bogotá’s school-system. Stratification of schools was based on school-type (i.e., private or public) and socioeconomic strata (SES) as ranked by the district Secretary of Education. Five selected schools refused to participate (82.1% response rate) and were randomly replaced by schools with similar sampling characteristics. Parental consent was obtained via a letter sent home explaining the purpose and content of the survey. Parents who did not want their child to participate were instructed to return a signed statement to the school. Regardless of parental approval, students who did not wish to participate in the study were free to opt out. Twelve parents refused their children’s participation in the study, 44 students declined to participate, and 88 were absent on the day of the survey and on subsequent survey days. Of those who participated (N = 2361), 82 returned incomplete questionnaires or provided incoherent or haphazard responses, or endorsed the opportunity to use a bogus drug (“Cadrina”, included as a quality control measure), and were excluded from the analysis, as were 200 respondents who indicated “don’t know” for the marijuana risk perception question. Compared with the 2079 questionnaires analyzed below, this group of 200 respondents was somewhat overrepresented by females (58.8%), public schools students (74.2%) and those who never used marijuana (97.3%). The research protocol was approved by university-based research committees in Colombia and Israel. 2.2. Data collection methods and study variables Data was collected via a standardized confidential questionnaire. Pilot studies including focus-group sessions appraised the suitability of the questionnaire with regard to duration, language appropriateness, construct comprehensiveness and answerability. During completion of the questionnaire in class, a research assistant answered questions about the survey and read each question aloud, which helped mitigate literacy barriers, maintain order in the classroom, enhance confidentiality, and gain the trust of the respondents to assure valid responses. The question used to assess perceived risk of regular marijuana use incorporated the “personal consequences” and “severity” dimensions (Danseco et al., 1999) used in the MTF questionnaire (Bachman et al., 1998), with a minor variation in the “level of use” dimension. Specifically, students were asked “To what extent do you think people risk harming themselves physically or psychologically, if they use marijuana

weekly?”. The original question was dichotomized as follows: “no risk” and “slight risk” were combined into “low perceived risk”, and “moderate risk” and “great risk” into “high perceived risk”, as suggested by the Inter-American Drug Abuse Control Commission (2009). Marijuana use was assessed by asking students “How old were you when you first tried marijuana?”; valid values were recoded into “ever marijuana users” and “non-users”. Ever marijuana users who reported using marijuana at least once every month within the last 12 months were classified as “monthly marijuana users”. Intention to use marijuana was assessed by the question “How likely is it that you will use marijuana in the next 12 months?”; possible answers included “not likely”, “likely” and “very likely”. Respondents who endorsed “likely” or “very likely” were considered to have “positive intentions”. Socio-demographic variables included in the analyses were: gender, age (<14, 14–16, >16 years), and family SES (low, medium, high). Known cognitive and psychosocial variables associated with substance use (Chilcoat and Anthony, 1996; Cleveland et al., 2005; Dormitzer et al., 2004; Guxens et al., 2007; Latimer et al., 2004) were also studied as independent variables. These included level of knowledge regarding physical and psychological harms of illegal drugs, level of problematic behavior, degree of parental supervision, past-year illicit drug use among firstdegree relatives, and number of drug-using friends (“none”, “one friend”, “a group of friends”). Level of knowledge was assessed by 6 questions (e.g., “Does illegal drug use lead to memory loss?”), analyzed in tertiles corresponding to all 6 questions answered correctly (high), 4–5 correct answers (medium) and <4 correct (low). Level of problematic behavior comprised 9 items (e.g., “During the last 12 months have you been in trouble with the police?”) analyzed in tertiles of 0–1, 2–3, and 4–9 problem behaviors endorsed. Degree of parental supervision was determined by 6 questions (e.g., “Are your parents or guardians often aware of where you are and what you are doing?”), analyzed in quartiles of 0–3, 4, 5, and 6 items endorsed. These three variables were also analyzed as continuous scales (respective Cronbach’s alpha coefficients for internal reliability of 0.75, 0.72 and 0.65), with similar results (not presented). Type of school (private or public), exposure to school-based drug prevention programs (yes or no), and availability of drugs in or around school (yes or no) were included in the analyses as school-related variables. 2.3. Analyses First-order statistics characterized the sample and ascertained the prevalence and determinants of perceived risk of using marijuana regularly. Associations are expressed as unadjusted odds ratios (OR) and adjusted odds ratios (AOR) with their corresponding 95% confidence intervals (CI) obtained from logistic regression models. Based on the premise that perceived risk predicts intention, and that intention to use precedes volitional use (Ajzen and Fishbein, 1980), and in order to eliminate the effect of past use on perceived risk and in some way overcome the temporal limitations of the cross-sectional nature of the study, analysis of the association between risk perception and intention to use marijuana within the next 12 months was restricted to respondents who had never used marijuana. Gender differences in risk perception and drug use were assessed by the Breslow-Day test for homogeneity of odds ratios. Analyses were performed using SPSS, version 15.0 (SPSS Inc., Chicago, IL).

3. Results 3.1. Sample characteristics The average age of participants was 14.7 years (SD = 1.2), 50% of the sample was male, and 66% studied in public schools (Table 1). Low perceived risk regarding regular marijuana use was reported by 11.2% of students, while nearly two-thirds (63.3%) perceived a “great” risk in using marijuana regularly. Ever use of marijuana was reported by 11.1% of respondents, of whom one-third (35.5%, or 3.9% of the total sample) used the drug monthly during the past year. Intention to use marijuana within the next 12 months was expressed by 10.0% of those who had never used marijuana, or 15.9% of the total sample. 3.2. Factors associated with low perceived risk of using marijuana regularly As seen in Table 2, variables independently associated with low perceived risk upon controlling for the effect of multiple confounders were: being male (AOR = 1.4, 95%CI = 1.0,1.9), age 14–16 years (AOR = 2.0, 95%CI = 1.1, 3.7) and >16 years (AOR = 2.9, 95%CI = 1.4, 6.0) compared with those younger than 14, medium

C. Lopez-Quintero, Y. Neumark / Drug and Alcohol Dependence 109 (2010) 65–72 Table 1 Characteristics of the study population of school adolescents in Bogotá, Colombia, 2006 (n = 2079). Characteristic

N

%

Gender Female Male

1021 1058

49.1 50.9

Age group (range = 12–21) <14 14–16 >16

265 1638 174

12.8 78.9 8.4

Socio-economic status Low Medium High

1129 700 247

54.4 33.7 11.9

Type of school Private Public

701 1378

33.7 66.3

level of knowledge about drug harms (AOR = 1.8, 95%CI = 1.2, 2.6) and low level of knowledge (AOR = 2.9, 95%CI = 2.0, 4.3) compared with students in the highest tertile of knowledge, high level of problematic behavior (AOR = 1.8, 95%CI = 1.2, 2.6), low parental supervision (AOR = 1.7, 95%CI = 1.1, 2.7), and having a group of friends who use drugs (AOR = 1.6, 95%CI = 1.1, 2.2). 3.3. Perceived risk and its association with marijuana use

Level of knowledge regarding the physical and psychological harms of illegal drug use (tertiles) 1st (low) 551 2nd 736 3rd (high) 780

26.5 35.4 37.5

Level of problematic behavior (tertiles) 1st (low) 2nd 3rd (high)

750 735 566

36.6 35.8 27.6

Parental supervision (quartiles) 1st (low) 2nd 3rd 4th (high)

512 469 589 478

25.0 22.9 28.8 23.3

Past-year illicit drug use among first-degree relatives No 1928 Yes 129

93.7 6.3

Number of drug-using friends None One A group of friends

48.7 12.5 38.8

1004 258 799

Exposure to school-based drug prevention programs No 751 Yes 1305

36.5 63.5

Availability of drugs in/around school No Yes

1169 905

56.4 43.6

Perceived risk of regular marijuana use High Low

1846 233

88.8 11.2

Perceived risk of regular marijuana use None Low Moderate Great

81 152 529 1317

3.9 7.3 25.4 63.4

Ever used marijuana No Yes

1841 231

88.9 11.1

Monthly marijuana use No Yes

1994 82

96.1 3.9

149 82

64.5 35.5

Monthly marijuana use among ever users No Yes

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Intentions to use marijuana within next 12 months No 1732 Yes 328

84.1 15.9

Intentions to use marijuana within next 12 months among never marijuana users No 1644 Yes 183

90.0 10.0

After controlling for the effects of multiple confounders, respondents who reported low perceived risk of using marijuana regularly were more likely to ever have used marijuana than respondents who reported high perceived risk (AOR = 2.5, 95%CI = 1.7, 3.7) (Table 3). Though somewhat stronger among females (AOR = 4.0, 95%CI = 2.1, 7.6) than males (AOR = 1.9, 95%CI = 1.2, 3.2), the difference in strength of association was not statistically significant (Breslow-Day p = 0.08). Among respondents who ever used marijuana, monthly marijuana use was more prevalent among those with a low risk perception of regular marijuana use than those with a high-risk perception (AOR = 2.7, 95%CI = 1.4, 5.0). Here too, the association among females (AOR = 4.1, 95%CI = 1.3, 13.3) was not significantly stronger than that among males (AOR = 2.3, 95%CI = 1.1, 4.8) (Breslow-Day p = 0.5). For the whole study population, the likelihood of being a monthly marijuana user was greater among respondents who reported low perceived risk than those who reported high perceived risk (AOR = 4.1, 95%CI = 2.4, 7.1). 3.4. Perceived risk and its association with intention to use marijuana In a subsidiary logistic regression analysis of the sub-sample of youth who never used marijuana (Table 3), those who perceived regular marijuana use to carry a low risk were 2.1 times more likely to express a positive intention to use the drug within the next 12 months than respondents who reported high perceived risk. The strength of this association was not significantly different (BreslowDay p = 0.5) between females (AOR = 2.0, 95%CI = 1.0, 4.2) and males (AOR = 3.2, 95%CI = 1.7, 6.0). 4. Discussion Just over 10% of our sample of school adolescents in Bogotá perceived regular use of marijuana to be a behavior that carries little or no risk. Medicinal use of marijuana notwithstanding, this finding is troubling in light of an increasing body of evidence suggesting short- and long-term deleterious effects associated with experimental and chronic marijuana use such as impaired cognitive function, acute psychotic reactions, anxiety, depression, and suicidal ideation (Gruber et al., 2003; Kalant, 2004; Moore et al., 2007; Schneider, 2008). Marijuana is also largely considered to be a “gateway” drug leading to the use of other drugs (Kandel et al., 1992; Polen et al., 1993; Tullis et al., 2003). Existing, although somewhat controversial, evidence also links chronic marijuana use with an increased risk of myocardial infarction, respiratory diseases and cancer (Hashibe et al., 2005; Mittleman et al., 2001; Tetrault et al., 2007). The effects of chronic marijuana use extend beyond the individual and his/her close social network, and pose a burden at the community/society level through an elevated risk of traffic accidents (Kalant, 2004; Ramaekers et al., 2004), an increased risk of sexually transmitted diseases (Boyer et al., 1999), poorer academic achievement (Brook et al., 2008), and lower income and higher unemployment (Fergusson and Boden, 2008). Although 63% of those surveyed perceive regular marijuana use to carry “great” risk, this rate is lower than that reported in all but one (Chile – 51.3%) of the countries studied in a multinational investigation of drug use patterns among South-American

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Table 2 Factors associated with low perceived risk of regular marijuana use among school adolescents in Bogotá, Colombia, 2006. Characteristics

Low perceived risk (N = 233)

OR

95%CI

AORa

95%CI

N

%

Gender Female Male

88 145

8.6 13.7

1.0 1.7

1.3–2.2

1.0 1.4

1.0–1.9

Age group <14 14–16 >16

14 186 33

5.3 11.4 19.0

1.0 2.3 4.2

1.3–4.0 2.2–8.1

1.0 2.0 2.9

1.1–3.7 1.4–6.0

Socio-economic status Low Medium High

116 87 29

10.3 12.4 11.7

1.0 1.2 1.2

0.9–1.7 0.8–1.8

Type of school Private Public

76 157

10.8 11.4

1.0 1.1

0.8–1.4

Level of knowledge regarding the harms of illegal drug use (tertiles) 1st (low) 98 17.8 2nd 80 10.9 3rd (high) 54 6.9

2.9 1.6 1.0

Level of problematic behavior (tertiles) 1st (low) 54 2nd 66 3rd (high) 107

7.2 9.0 18.9

1.0 1.3 3.0

Parental supervision (quartiles) 1st (low) 2nd 3rd 4th (high)

16.2 11.7 9.5 6.9

2.6 1.8 1.4 1.0

Past-year illicit drug use among first-degree relatives No 210 Yes 23

10.9 17.8

1.0 1.8

1.1–2.9

1.0 1.4

0.8–2.2

Number of drug-using friends None One A group of friends

7.8 8.9 16.0

1.0 1.2 2.3

0.7–1.9 1.7–3.1

1.0 1.1 1.6

0.6–1.7 1.1–2.2

Exposure to school-based drug prevention programs No 96 Yes 141

12.0 10.8

1.0 1.1

0.9–1.5

Availability of drugs in/around school No 122 Yes 111

10.4 12.3

1.0 1.2

0.9–1.6

83 55 56 33

78 23 128

2.0–4.1 1.1–2.4

0.9–1.9 2.1–4.3 1.7–4.0 1.1–2.8 0.9–2.2

2.9 1.8 1.0 1.0 1.1 1.8 1.7 1.3 1.2 1.0

2.0–4.3 1.2–2.6

0.7–1.5 1.2–2.6 1.1–2.7 0.8–2.0 0.8–1.9

Notes: OR = odds ratio; AOR = adjusted odds ratio; CI = confidence interval. a Adjusted for variables found to be significantly associated in the univariate analyses.

schoolchildren (Inter-American Drug Abuse Control Commission, 2004), where the proportion that reported great perceived risk ranged from 72.8% in Bolivia to 80.7% in Paraguay. These countries show a strong negative correlation between level of “great” perceived risk and prevalence of life-time marijuana use (Pearson’s correlation coefficient = −0.844, p = 0.008). Chronic exposure to civil conflict, a context of high-drug production, the high prevalence of mental health disorders, and inconsistent judicial policies regarding penalization of drug users and traffickers (Brook et al., 1998; Demyttenaere et al., 2004; Siqueira and Brook, 2003; Thoumi, 2002) may have blunted the perception of risk associated with drug use among youth in Colombia, resulting in increased use in relation to the other South-American countries. Boys and older students tended to exhibit lower levels of perceived risk of regular marijuana use, as has been previously documented (Cohn et al., 1995; Danseco et al., 1999; Pascale and Evans, 1993). Students in the oldest age group (>16 years) were nearly three times more likely to report low perceived risk than those in the youngest age group. These age and gender differences in risk perception may stem from feelings of invincibility – partic-

ularly among males, a tendency of males to embrace risk as part of their socialization process, and exposure to drug-using peers, all of which are common during middle and late adolescence (Graham et al., 1991; Greening et al., 2005; Pascale and Evans, 1993). Level of knowledge regarding the psychological and physical effects of illegal drugs, friends’ drug use and problematic behavior are known to be correlated with drug use among adolescents and to influence attitudes and beliefs regarding drug use (Guxens et al., 2007), as they were in this sample of Bogotá’s youth. Consistent with previous findings (Bachman et al., 1998; Johnston et al., 2005), students in Bogotá who reported low perceived risk of using marijuana regularly were 2.5 times more likely to ever have used marijuana, and 4 times more likely to be monthly marijuana users than those who perceive this to be a high-risk behavior. Furthermore, ever marijuana users who reported low perceived risk were 2.7 times more likely to be monthly marijuana users than those who reported high perceived risk. Adolescents who are less aware of the hazardous effects of marijuana or who have not personally witnessed or experienced negative consequences associated with its use, may be more prone to initiate

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Table 3 Associations between perceived risk of regular marijuana use and (1) ever use of marijuana; (2) monthly marijuana use among ever marijuana users; (3) intentions to use marijuana in the next 12 months among never marijuana users; among the total study population and stratified by gender: results of logistic regression analyses, 2006. Perceived risk

Ever use of marijuana N = 231

Monthly marijuana use among ever marijuana users N = 82

Intentions to use marijuana among never marijuana users N = 183

%

OR (95%CI)

AORa (95%CI)

%

OR (95%CI)

AORb (95%CI)

%

OR (95%CI)

AORc (95%CI)

Total High Low

8.7 30.3

1.0 4.5 (3.3–6.3)

1.0 2.5 (1.7–3.7)

28.6 51.4

1.0 2.7 (1.5–4.7)

1.0 2.7 (1.4–5.0)

9.1 19.7

1.0 2.5 (1.6–3.8)

1.0 2.1 (1.4–3.5)

Females High Low

5.9 28.4

1.0 6.3 (3.7–10.8)

1.0 4.0 (2.1–7.6)

23.6 52.0

1.0 3.5 (1.3–9.5)

1.0 4.1 (1.3–13.3)

10.1 19.0

1.0 2.1 (1.1–4.1)

1.0 2.0 (1.0–4.2)

Males High Low

11.6 31.5

1.0 3.5 (2.3–5.2)

1.0 1.9 (1.2–3.2)

31.1 51.1

1.0 2.3 (1.1–4.7)

1.0 2.3 (1.1–4.8)

8.0 20.2

1.0 2.9 (1.7–5.1)

1.0 3.2 (1.7–6.0)

Notes: OR = odds ratio; AOR = adjusted odds ratio; CI = confidence interval. Models are adjusted for variables found to be significantly associated with each outcome at the univariate level. a Adjusted for gender, age, SES, problematic behavior, parental supervision, past-year illicit drug use among first-degree relatives, number of drug-using friends, and availability of drugs in/around school. Gender-specific models exclude gender as a covariate. b Adjusted for problematic behavior and number of drug-using friends. c Adjusted for age, SES, level of knowledge about harms of illegal drug use, problematic behavior, parental supervision, past-year illicit drug use among first-degree relatives, number of drug-using friends, exposure to school-based drug prevention programs, and availability of drugs in/around school.

use. On the other hand, those aware of the negative effects of marijuana use or who have witnessed or experienced negative effects, may adapt their beliefs to serve their own habits by using self-protective and self-enhancement motives (Agostinelli et al., 1992; Agostinelli and Miller, 1994). Specifically, these individuals may tend to deny their susceptibility to experience deleterious consequences, interpret the negative consequences as innocuous, normalize the behavior through false consensus effect mechanisms, or attribute the consequences to factors beyond their own control (Agostinelli et al., 1992; Agostinelli and Miller, 1994; Gerrard et al., 1996; Halpern-Felsher et al., 2004; Sjöberg, 1998; Wolfson, 2000). Additionally, among individuals using marijuana regularly, delay discounting mechanisms (i.e., the inability to resist temptation of an immediate smaller reward in lieu of receiving a larger reward at a later date, Ainslie, 1975) might bias their judgment of the hazards resulting from their behavior. Informing youth about acute and long-term consequences associated with drug use has been instrumental in raising the level of risk awareness regarding the hazardous effects of drugs, and diminishing “first-order denial” of health risks (“disavowal of the primary facts of an illness”, Weisman, 1989), independent of the person’s own drug use status. Knowledge enhancement has also been shown to be effective in reducing the risk of drug use onset, when employed in conjunction with normative re-education strategies and training in refusal, social and communication skills (Agostinelli et al., 1995; Faggiano et al., 2005; Neighbors et al., 2004; Tobler, 1997). A positive intention to use marijuana within the next 12 months was expressed by 16% of the total sample and 10% of students who never used marijuana. In light of the evidence demonstrating that adolescents who express positive intentions toward drug use are three to five times more likely to initiate marijuana use than those with negative intentions (Crano et al., 2008; Von Sydow et al., 2002), this high-risk group warrants special attention to prevent the transition from intention to actual use. Respondents who never used marijuana but perceived its regular use as low risk, were twice as likely to express positive intentions to use marijuana within the next year than non-users with a high-risk perception. This suggests that the relationship between perceived risk and marijuana use is not mediated exclusively by the cognitive effect derived from previous drug use experiences, but also by a preconceived set of beliefs, subjective norms, attitudes and cognitions originated from processes of vicarious learning (Skenderian et al., 2008). Previous research has documented the impact of peer beliefs, attitudes and

behaviors as well as self-perception of other’s behaviors on initiation and maintenance of substance use (Kilmer et al., 2006; Olds et al., 2005; Perkins et al., 1999; Perkins, 2002; Wolfson, 2000). Experimental evidence indicates that in contrast to beliefs derived from previous direct experiences, beliefs originating from second-hand information are less strong, less stable over time, and less influential over behavior performance (Ajzen, 2001). Understanding the content and origin of these beliefs is essential to develop effective interventions aimed at reinforcing positive behaviors among non-users. 4.1. Strengths and limitations Our results extend the current level of knowledge about drug use and its antecedents among school-attending adolescents in Bogotá, and provide an epidemiologic basis for policy development. The estimates of life-time marijuana use observed in this study are similar to those observed in a national school survey in 2004 (InterAmerican Drug Abuse Control Commission, 2004), suggesting that the present sample reasonably represents the general population of Colombian school-attending adolescents. At the same time, some limitations of the study warrant mention. The usual degree of caution associated with interpretation of self-reported behaviors, which may render the results susceptible to social desirability bias (Anthony et al., 2000) must be applied. We anticipate that any bias in the reporting of drug use would be toward under-reporting the use of illegal drugs. As with all school-based research, the findings may not generalize to adolescents who do not attend school who may be at higher risk of using drugs (Turner et al., 1992), although nearly 90% of Bogotá’s children and youth attend school (Secretaria de Educacion de Bogotá, 2003). Absenteeism rates observed in this study were probably slightly higher than in previous years, due to the city-wide public school renovation program that caused disruption in academic activities of many schools. Perceived risk was assessed based on a standardized single question, which precluded exploration of the multiple dimensions of this construct (Danseco et al., 1999) and their specific effects on use. A more comprehensive assessment of risk perception is needed in view of the complexity and importance of this construct in the designing of prevention strategies. Finally, the cross-sectional nature of this study does not allow us to assess the stability of beliefs and attitudes over time and as the youth pass through adolescence, and how such changes might

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impact on marijuana use and intentions to use. Additional studies are needed to explore these issues, the role of self-serving biases in influencing risk perception, and gender-specific mechanisms that may mediate the association between perceived risk and drug use. 4.2. Conclusions and recommendations Results of this study suggest that perception of regular marijuana use as a high-risk behavior functions as a protective factor against the use of marijuana and intention to use. Worrisomely, a significant proportion of adolescents in Bogotá harbor misperceptions regarding the physical and psychological consequences of regular marijuana use, which may hamper their ability to make informed decisions about engaging in drug-using behaviors. To be effective, drug use prevention strategies must address the individual and his/her surrounding micro- and macro-social environment (U.S. Department of Health and Human Services, 2003). Implementation of effective prevention programs is particularly urgently needed in an environment in which limited resources can be allocated to the treatment of mental health conditions, such as in Colombia (Demyttenaere et al., 2004) where the use of illegal drugs is on the rise and the age of drug use initiation is dropping (Brook et al., 2003; Inter-American Drug Abuse Control Commission, 2004; Trujillo et al., 2007). Comprehensive school-based programs that provide students with refusal and intra- and inter-personal social skills (Botvin and Griffin, 2007; Faggiano et al., 2005; Tobler, 1997) have been shown to be effective in modifying drug use perceptions among program recipients (Black et al., 1998), and most importantly in reducing drug use incidence (Botvin and Griffin, 2007; Faggiano et al., 2005; Tobler, 1997). Notably, however, exposure to school-based drug prevention programs in Bogotá was not associated with perceived risk, implying the need to assess the content of existing programs. Health promotion strategies proposed within the framework of Colombia’s new national drug policy (Ministerio de Proteccion Social, 2007) should intensify activities aimed at educating youth in identifying the potential immediate and chronic individual risks and social harms associated with marijuana use, and the risks of progressing from experimental use to regular use during adolescence. Such educational activities must avoid presenting outdated, inaccurate and exaggerated information regarding the risk of experiencing a particular outcome and its severity, which might negatively impact on the adolescent’s behavior (Skenderian et al., 2008). Specifically for current users, raising awareness through a non-judgmental and non-confrontational approach that matches adolescents’ level of readiness and ability to change (self-efficacy), such as that proposed in motivational enhancement therapy, could help in decreasing use (Lott and Jencius, 2009; Miller et al., 1995; Miller and Rollnick, 2002; Martin and Copeland, 2008). Macro-level public health interventions, particularly those with a high degree of public attention (usually achieved by mass media) are effective in amplifying or attenuating perceptions of risk and safety (Bala et al., 2008; Kasperson et al., 1988; Sowden and Arblaster, 2000; Sutfin et al., 2008; Wakefield et al., 2003; Zhao et al., 2006). Data from the ongoing MTF study in the USA, for example, indicate that changes in perceived risk of marijuana use that occurred between 1976 and 1996 may account for the secular changes in marijuana use observed during those two decades. The increase in the perception of marijuana use as a risky behavior paralleled a steady decrease in use until the early 1990s when this trend reversed and the prevalence of use began to increase. The shifts in risk perception have been attributed to changes in news coverage of drugs issues and the magnitude and impact of anti-drug campaigns (Bachman et al., 1998; Johnston et al., 2005). These findings indicate that modifying the social perception of risk

regarding the hazardous effects of drugs within the Colombian context demands the involvement of multiple actors, principally the media, and the design of comprehensive evidence-based health promotion strategies. Establishment and reinforcement of social and legal regulatory frameworks is needed to assure that coherent educational messages are provided. Despite the worrisome trends of adolescent drug use observed in Colombia, less than 5% of the national drug budget is allocated to prevention and treatment (Alvarado and Lahuerta, 2005). Achievement of Colombia’s new national drug policy goals (Ministerio de Proteccion Social, 2007) requires a re-balancing of resources allocated for drug use prevention and for combating drug trafficking. Organizations responsible for drug use prevention and monitoring need to be strengthened and additional supportive structures created in order to respond to the drug use trends observed in Colombia. Conflict of interest The authors declare that they have no conflicts of interest. Role of funding sources The preparation, development of this work was funded by a Milstein Doctoral Training Fellowship to C. Lopez-Quintero at the Hebrew University-Hadassah Braun School of Public Health and Community Medicine. Additional funds for data analyses were provided by the Inter-American Drug Abuse Control Commission (CICAD) and the National Institute on Drug Abuse (NIDA) through the NIDA/CICAD Competitive Research Award Fund. The funding sources had no further role in the study design; in the collection, analysis and interpretation of data; in the writing of the report or in the decision to submit the paper for publication. Contributors Lopez-Quintero C and Neumark Y designed the study, undertook the statistical analysis and wrote the manuscript. Acknowledgements The authors wish to thank the schools and students who participated in the survey and the local health authorities for their cooperation. References Ainslie, G., 1975. Specious reward: a behavioral theory of impulsiveness and impulse control. Psychol. Bull. 82, 463–496. Ajzen, I., 2001. Nature and operation of attitudes. Annu. Rev. Psychol. 52, 27–58. Ajzen, I., Fishbein, M., 1980. Understanding Attitudes and Predicting Social Behavior. Prentice-Hall, NJ. Ajzen, I., Timko, C., White, J.B., 1982. Self-monitoring and the attitude–behavior relationship. J. Pers. Soc. Psychol. 42, 426–435. Alvarado, L.E., Lahuerta, Y., 2005. Comportamiento del gasto del estado colombiano en la lucha contra las drogas: 1995–2004. Bogotá, Colombia. Dirección Nacional de Estupefacientes, Departamento Nacional de Planeación, Bogotá, Colombia. Agostinelli, G., Sherman, S.J., Presson, C.C., Chassin, L., 1992. Self-protection and selfenhancement biases in estimates of population prevalence. Pers. Soc. Psychol. Bull. 18, 631–642. Agostinelli, G., Miller, W.R., 1994. Drinking and thinking: how does personal drinking affect judgments of prevalence and risk? J. Stud. Alcohol 55, 327–337. Agostinelli, G., Brown, J.M., Miller, W.R., 1995. Effects of normative feedback on consumption among heavy drinking college students. J. Drug Educ. 25, 31–40. Anthony, J.C., Neumark, Y.D., Van Etten, M.L., 2000. Do I do what I say? A perspective on self-report methods in drug dependence epidemiology. In: Stone, A., Turkan, J.S., Bachrach, C.A., Jobe, J.B., Kurtzman, H.S., Cain, V.S. (Eds.), The Science of Self-Report: Implications for Research and Practice, 1st ed. Lawrence Erlbaum Associates, Mahwah, NJ, pp. 175–198.

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