European Journal of Public Health, 1–6 ß The Author 2015. Published by Oxford University Press on behalf of the European Public Health Association. All rights reserved. doi:10.1093/eurpub/ckv115
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Factors associated with the prevalence of adolescent binge drinking in the urban areas of Greater Manchester Panchami Elisaus, Greg Williams, Michael Bourke, Gary Clough, Annie Harrison, Arpana Verma Manchester Urban Collaboration on Health, Centre for Epidemiology, Institute for Population Health, Manchester Academic Health Science Centre, The University of Manchester, Manchester M13 9PT, UK Correspondence: Arpana Verma, Manchester Urban Collaboration on Health, Centre for Epidemiology, Institute for Population Health, Manchester Academic Health Science Centre, The University of Manchester, Manchester M13 9PT, UK, Tel: +44 (0)161 275 5206, e-mail:
[email protected]
Background: Binge drinking in adolescents is a serious problem that has been recognised for over a generation. On average 61% of students in the European region had consumed alcohol in the last 30 days and 43% had participated in binge drinking in the same period. This article investigates the prevalence of adolescent binge drinking and the factors associated with this prevalence in urban areas of Greater Manchester. Methods: Data were obtained from the youth survey of the European Urban Health Indicator System 2 project. Study participants were school students aged 14–16 from the urban areas of Greater Manchester. The main outcome measures were adolescent binge drinking prevalence in Greater Manchester and the socio-demographic factors influencing it. Results: Greater Manchester had an adolescent binge drinking prevalence of 49.8%. Individual factors associated with increased prevalence of binge drinking were: age, substance use, school performance and early initiation of drinking (all significant at 2, P < 0.05). Peer factors associated with increased prevalence of binge drinking were spending evenings with friends, keeping in touch with friends, having a good relationship with peers and selfreported bullying behaviours (all significant at 2, P < 0.05). Family support lowered the prevalence of adolescent binge drinking. Conduct problems, family affluence and perceived local crime increased the prevalence of adolescent binge drinking. Conclusions: Binge drinking is highly prevalent in Greater Manchester adolescents. Various individual, peer-related, family-related and community-related factors were associated with this problem. Any attempt to tackle the prevalence of adolescent binge drinking must take into account all of these factors.
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Introduction inge drinking is a serious problem, with harmful use of alcohol
Bcausing 3.3 million deaths every year globally (5.9% of all
deaths).1 In UK, binge drinking is defined as consuming eight or more units for males, or six or more units for females in a single drinking session (with one unit of alcohol defined as 10 ml of pure alcohol2). There is no specific definition of binge drinking for adolescents.3 In this study the European School Survey Project in Alcohol and Other Drugs (ESPAD) definition for adolescent binge drinking will be used, that of five or more units in a single drinking session.4 The prevalence of Adolescent Binge Drinking (ABD) varies based on the population studied, and the definition of binge drinking and adolescence used. In 2007, the ESPAD study investigated the drinking habits of over 100 000 adolescents.4 The study found that on average 61% of students in the European region had consumed alcohol in the last 30 days and that 43% had participated in binge drinking in the same period.4 Binge drinking was more common among boys than girls.4 Compared with other countries, the prevalence of binge drinking in UK was relatively high, and the rates reversed with 52% of boys and 55% of girls reporting binge drinking in the last 30 days.4 ABD is associated with significant mortality and morbidity.5 Acute health consequences associated with binge drinking in adolescents include unintentional injuries and alcohol poisoning.6 In the longer term, prolonged binge drinking can result in permanent damage to brain structures.7 It can also lead to alcohol dependence, difficulties with interpersonal relationships and further health problems.5,8 Binge drinking in adolescence can also
result in chronic problems such as ‘alcohol dependence, liver disease, high blood pressure, heart attack, stroke and certain kinds of cancer’.6–10 Despite the many negative consequences of binge drinking, it remains highly prevalent. In this study, factors that are associated with the prevalence of ABD were split into individual, peer, family and other factors. Individual factors that have an association with binge drinking in adolescence include age, with higher rates associated with being older,9,11–14 early puberty,15 early age alcohol use13 genetic susceptibility16 ethnicity,6,9,11,17 low religiosity,6,18 truancy,19 working many hours part-time,20 low academic achievement9,21,22 and use of other illicit substances.9,13,19 Gender was found to yield conflicting results; some studies found females,9,11 and some found males to be at increased risk.12,13,17,22 The role of peers on an adolescent’s drinking habits become increasingly important as s/he gets older.23 Studies suggest youths imitate the drinking behaviours of their peers during adolescence, in an attempt to conform to perceived norms.11,22,24 Peer-related factors that have an association with ABD include a high proportion of alcohol-using friends, offers of alcohol and encouragement to drink by peers, and frequent unstructured peer interaction.6–8,11,19,24,25 Another factor is the beliefs and perceptions the adolescent holds regarding their peers’ drinking habits,5,6,9,13 with studies showing that adolescents tend to overestimate alcohol-use in peers and that this leads to a higher prevalence of ABD.5,6,13,24 There is no definite conclusion regarding the role of parents in ABD currently within the literature.6–8,13,21,22,24 Parental monitoring and support is known to be protective,8,22,24,25 and is thought to be due to a resultant decrease in adolescent involvement in risky behaviour and with deviant peers.22 Parental drinking,21,25 alcohol
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use by an older sibling9 and being from a single parent family11 were other familial factors associated with an increased ABD. Other factors included psychiatric problems, the media, and the local community which all play a role in ABD.9,12,26,27 The media is increasingly implicated as a contributory factor to adolescent drinking, but few studies have looked into the effect of the media on binge drinking.12 However, Morgenstern concluded that binge drinking was positively associated with exposure to alcohol related advertisements.12 Community characteristics play a role in ABD.26 The aim of this study is to investigate the factors that are associated with the prevalence of adolescent binge drinking in Greater Manchester (GM).
Methods The data were obtained from the 2010–11 cross-sectional youth survey of the European Urban Health Indicators System Part 2 (EURO-URHIS 2) research project. The youth survey methods are reported in more detail in ‘Collecting standardised urban health indicator data at an individual level for school-aged children living in urban areas: methods from EURO-URHIS 2’,28 but briefly, a questionnaire was completed by 15 1-year-old school students in 30 urban areas across Europe. For this study, data from 3466 students registered at 37 schools in Greater Manchester (GM) was analysed. The main outcome measure for alcohol was the prevalence of binge drinking, defined as drinking five or more units of alcohol on at least one occasion in the last 30 days. Other alcohol related variables studied included having ever drunk alcohol in their lifetime, having had at least one glass of alcohol by the age of 13, having drunk alcohol in the last 30 days and having been intoxicated in the last 30 days. The individual characteristics studied in this article included gender, age, school performance, tobacco use and cannabis use. Peer factors considered were having good friends, being liked by peers, being able to communicate with peers, evenings spent with peers, contact with peers using technology, being bullied and being a bully. Family factors studied were ease of communication with one’s parents. Other factors investigated included television exposure, having conduct and emotional problems (each label given based on answers to questions regarding feelings and behaviour) and worrying a lot. The roles of community characteristics were also studied; crime in the neighbourhood and family affluence score were used as representative variables. All studied characteristics, other than peer relations, were chosen based upon literature that had identified associations between these variables and ABD. Studies have investigated the impact of peer drinking habits and perception of peer drinking habits on adolescent’s drinking patterns, however the role of peer relations has not been studied. This study hypothesises that peer relations have an impact on ABD. Statistical analysis was carried out using SPSS 16.0. Prevalence was calculated for the different categories of the variables by dividing the responses to the survey questions (numerator) by the number of survey participants (denominator). To assess whether statistical differences were present, chi-square ( 2) test was used for each variable.
Results There were 3466 students surveyed in GM; 1615 (46.6%) were males and 1851 (53.4%) females. The mean age of the population was 14.97 (range 14–16). The relevant baseline characteristics of the students sampled can be seen in table 1. Drinking habits of the students surveyed can be seen in table 2, which shows the rate of binge drinking as 49.8%, with a higher rate
in females (50.6%) than in males (49.0%). Of all students, 31.7% reported being intoxicated in the last 30 days.
The role of individual factors Individual factors significantly associated with higher prevalence of ABD were: increased age ( 2, P = 0.001; 42.1% vs. 50.6% vs. 53.8%); tobacco smoking ( 2, P < 0.001; 74.4% vs. 34.4%); cannabis use ( 2, P < 0.001; 81.1% vs. 39.9%); and early initiation of alcohol use ( 2, P < 0.001; 68.3% vs. 23.2%); The individual factor significantly associated with lower prevalence of ABD was: academic performance ( 2, P < 0.001), a lower proportion of students who rated their school performance as ‘good’ or ‘very good’ reported binge drinking compared to those who rated their performance as ‘average’ or ‘poor’ (46.1% vs. 59.8%). Gender was not significantly associated with ABD.
The role of peer factors Peer factors significantly associated with higher prevalence of ABD were: perceiving that other people their age liked them ( 2, P = 0.007; 50.3% vs. 38.7%); finding it ‘easy’ or ‘very easy’ to talk to friends ( 2, P < 0.001; 50.9% vs. 32.9%); spending three or more evenings with friends ( 2, P < 0.001; 61.3% vs. 35.2%); contacting friends using technology on three or more days a week ( 2, P < 0.001; 52.9%); and having bullied others in the last couple of months ( 2, P < 0.001; 62.5% vs. 47.3%) (figure 1). Peer factors significantly associated with lower prevalence of ABD were: being bullied in the last couple of months ( 2, P = 0.008; 44.6% vs. 50.9%). ABD was not significantly associated with having one or more good friends.
The role of family relations on ABD Finding it easy to talk to parents was significantly associated with lower prevalence of ABD: finding it ‘easy’ or ‘very easy’ to talk to your mother ( 2, P = 0.032; 49% vs. 53.5%) or father (45.8% vs. 54.6%)
Other factors Other factors significantly associated with higher prevalence of ABD were: having conduct problems ( 2, P < 0.001; 63.5% vs. 45.4%); the perceived amount of crime in the area ( 2, P < 0.001; 55.0% vs. 45.9%); higher family affluence (rated high, medium or low according to the Family Affluence Scale, WHO Europe—http:// www.euro.who.int/__data/assets/pdf_file/0005/53852/E91416.pdf; 2, P < 0.001 and 2, P < 0.001; 54.2% vs. 45.2% vs. 41.5% respectively) (figure 2). Emotional problems and worrying a lot were not significantly related to ABD. Exposure to media was not significantly associated with ABD. These results are illustrated in figure 2.
Discussion Adolescent alcohol use and binge drinking were highly prevalent in the urban areas of GM. However, the prevalence of ABD had slightly declined compared to national figures from 2007.4 This decrease could be attributed to a slow decrease in the prevalence of ABD in England, or an indicator of geographical variation. As a crosssectional study, the findings of EURO-URHIS 2 will not show whether the declining trend will continue, but the positive implications of such a trend show that a longitudinal study would be appropriate. Many individual factors were found to be associated with an increased prevalence of ABD in GM. The factors included being older, a tobacco smoker, a cannabis user, a poor performer at
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Table 1 Baseline characteristics of the sampled population Variable
Number (%)
Missing data (%)
Total population Individual factors Gender Males Females Age 14 15 16 Had smoked tobacco in lifetime Had taken cannabis in lifetime Had good/ very good school performance Peer factors Had one or more good friends Thought other people their age generally liked them Found it easy/ very easy to talk to friend(s) Spent three or more evenings a week with friends Used technology on three or more days a week to keep in touch with friends Had been bullied at least once in the last couple of months Had bullied at least once in the last couple of months
3466 (100)
0.0
478 (13.8) 2624 (75.7) 364 (10.5) 1328 (38.5) 766 (23.2) 2516 (74.4)
0.6 4.8 2.5
3344 (97.2) 3283 (95.7) 3214 (95.4) 1876 (55.7) 2973 (87.4) 524 (15.7) 551 (16.6)
0.7 1.0 2.4 2.8 1.9 4.0 4.5
Variable
Number (%)
Missing data (%)
1745 (59.5) 2532 (77.6)
3.4 3.3
2165 (65.5) 838 (24.2) 632 (18.3) 2285 (66.0)
4.7 0.1 0.1 0.5 3.7
0.0 1615 (46.6) 1851 (53.4) 0.0
Familial factors Found it easy/ very easy to talk to father(12.0% did not have/ see this person) Found it easy/ very easy to talk to mother(2.6% did not have/ see this person) Other factors Watched television for two or more hours on a school day Had conduct problems Had emotional problems Worried a lot Family affluence score Low Medium High Had crime in their area
282 (8.5) 1216 (35.1) 1839 (53.1) 1469 (44.1)
3.9
Table 2 Drinking patterns of the sampled population Drinking pattern
Prevalence in sampled population (%)
Missing data (%)
Drunk at least once in lifetime Drunk alcohol in the last 30 days Drunk five or more units of alcohol on the same occasion in the last 30 days Intoxicated in lifetime Intoxicated in the last 30 days Drunk at least one glass of alcohol by age of 13
2666 1998 1670 1898 1018 1940
5.0 2.4 3.3 5.0 7.5 7.9
school and commencing alcohol use at an early age. These findings were in keeping with previous studies.9,11–14,19,21,22 Gender didn’t have a significant association in this study. Spending evenings with friends was found to have a significant impact on ABD; this mirrored the findings of other studies.8,19 Using technology to keep in touch with friends, finding it easy to talk to friends, and perceiving yourself as being liked by peers were factors associated with ABD. Bullying played an important role in the prevalence of ABD, with students not being bullied and students who were bullies more likely to binge drink. The peer related findings of this study implied that binge drinking was a behaviour that was prevalent in adolescents who had good relationships with their peers. Findings suggested that binge drinking was perceived by adolescents as a normal part of socialisation. The influence of peers in ABD implies that interventions targeting peer networks could give rise to exponential improvements in drinking behaviour amongst adolescents.
(80.9) (59.1) (49.8) (57.7) (31.7) (60.8)
Finding it easy to talk to your parents was found to be a protective factor against ABD; communication with one’s father was noted as particularly important. Similar findings have been reported by Piko et al.22 Associations have been found between psychiatric problems and an increased risk of binge drinking.27 However, in this study no association was found in students with emotional problems or students who worried a lot. However, there was an association between binge drinking and students with conduct problems. Alcohol related media has often been blamed for playing a role in the high prevalence of adolescent alcohol use and in the earlier initiation of alcohol12 Our study found no significant association between the prevalence of ABD and watching television but no data was collected on what was being watched. In keeping with the findings of other studies, community characteristics were found to play a role in the prevalence of ABD in GM.26 There was a positive correlation between the level of family affluence and the prevalence of ABD. This association was in keeping with the
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Figure 1 Prevalence of adolescent binge drinking in populations with differences in peer factors (*Significant at P < 0.05). (a) Have one or more good friends. (b) Other people my age generally like me. (c) Find it easy/ very easy to talk to friends. (d) Spend 3 or more evenings a week with friends. (e) Contact friends 3 or more days a week with technology. (f) Been bullied in the last couple of months. (g) Bullied in the last couple of months
Figure 2 Relationship between various factors and adolescent binge drinking (*Significant at P < 0.05)
findings reported by Chuang et al.29 Crime in an area was another factor found to be associated with a higher prevalence of ABD. This finding was in keeping with the findings of Wilson et al.23 The negative short-term and long-term consequences associated with ABD demonstrate the wider implications on the healthcare system and society if ABD is not fully addressed.
Strengths of the study The strengths of this study included the data being specific to the urban areas of GM, the large and varied sample population, the use of previously validated and piloted questions, the anonymisation of
questionnaires, the collection of comparable data and the measures taken to minimise data collection errors. This investigation of the factors that are associated with the prevalence of ABD in GM, is an important contribution to the literature, as there have been few English studies on this topic, despite the knowledge that socio-demographic factors affect the prevalence of ABD. Questions used in the EURO-URHIS 2 study were validated and some had been used previously by the HBSC study.28 Since the HBSC study was carried out on a population similar to that of the EURO-URHIS 2 study,30 the use of their questions supported the argument that questions in the survey were appropriate and reliable.
The prevalence of adolescent binge drinking in the urban areas of Greater Manchester
The same protocol was used throughout the EURO-URHIS 2 survey, allowing for within and between country comparisons. This creates opportunities for further analysis leading to strategies to reduce the prevalence of ABD.
Limitations of the study The study was cross-sectional, therefore we could conclude that there were significant associations between certain variables and ABD but could not establish a cause and effect relationships. While all the questions used in the EURO-URHIS 2 study had been previously validated28 not all of them were specific to this study. This meant that the answers to non-specific questions were used as proxies. For example, ‘I worry a lot’ was used as a proxy for anxiety. This introduced a possibility that the findings were not accurate. Another limitation in this study was that certain labels were given to pupils based on their answers to questions rather than by using diagnoses. Students were labelled as having conduct problems based on their answers to questions. While this form of labelling has been previously used, the lack of clinical judgement in the making of the diagnosis means that the possibility of bias remained. Another potential source of misclassification bias in this study was the use of two or more hours of daily television watching as a measure of exposure to alcohol related advertisements and media. Only findings from GM were included in this study which means that any generalisations drawn from this study might be biased. The survey was carried out only on one day in each school. Adolescents who were not in school on the day of the survey were exempted from the study. Since all the data collected in this study was self-reported, misreporting was a possible source of data errors. This is a limitation that is difficult to avoid in questionnaire-based studies. The omission of stepfathers and stepmothers from the analysis of the influence of family support on ABD was a limitation. Ethnicities of students in the sample population were not recorded. This was a limitation as it meant that it was unclear whether the ethnic minorities had been appropriately represented.
institutions. (Full details of all project partners can be found on http://urhis.eu/euro-urhis1/ & http://urhis.eu/).
Funding This research project was co-funded by EU Commission, under the 7th Framework Programme (FP7/2007–2013) as part of the EUROURHIS 2 project (grant agreement no 223711) and the project beneficiaries. Conflicts of interest: None declared.
Key points Adolescent alcohol use and binge drinking were highly prevalent in the urban areas of GM. Being older, a tobacco smoker, a cannabis user, a poor performer at school and commencing alcohol use at an early age was significantly associated with adolescent binge drinking. Findings suggested that binge drinking was perceived by adolescents as a normal part of socialisation. Binge drinking in adolescence is a prevalent problem that needs to be addressed using a multi-modal approach.
References 1
Choices N. Binge drinking. NHS; 2012 [cited 2014 18/09/2014].
2
Choices N. Alcohol units. NHS; 2013. Available from: http://www.nhs.uk/Livewell/ alcohol/Pages/alcohol-units.aspx (18 September 2014, date last accessed).
3
Courtney KE, Polich J. Binge drinking in young adults: data, definitions, and determinants. Psychol Bull 2009;135:142–56.
4
Hibell B, Guttormsson U, Ahlstrom S, et al. The 2007 ESPAD Report. Substance use among students in 35 countries ESPAD, 2009.
5
Page RM, Ihasz F, Hantiu I, et al. Social normative perceptions of alcohol use and episodic heavy drinking among Central and Eastern European adolescents. Substance Use Misuse 2008;43:361–73.
6
Stevens-Watkins D, Rostosky S. Binge drinking in African American males from adolescence to young adulthood: the protective influence of religiosity, family connectedness, and close friends’ substance use. Substance Use Misuse 2010;45:1435–51.
7
Martino SC, Ellickson PL, McCaffrey DF. Multiple trajectories of peer and parental influence and their association with the development of adolescent heavy drinking. Addictive Behav 2009;34:693–700.
8
Crawford LA, Novak KB. Parental and peer influences on adolescent drinking: the relative impact of attachment and opportunity. J Child Adolesc Substance Abuse 2002;12:1–26.
9
D’Amico EJ, Metrik J, McCarthy DM, et al. Progression into and out of binge drinking among high school students. Psychol Addict Behav 2001;15:341–9.
Conclusion This study investigated the role of various factors on the prevalence of ABD in the urban areas of GM. Findings showed that binge drinking was highly prevalent and that drinking appears to be a norm amongst adolescents in GM. Various individual, peer, family and community related factors were found to play a role. Factors associated with increased prevalence of ABD included those related to an active social life as well as negative behaviours such as smoking tobacco, using cannabis, and bullying. Over 60% of adolescents reported early initiation of alcohol use and this was associated with an increased prevalence of binge drinking. The study shows factors that are associated with ABD, which can be used to target interventions appropriately. Possible interventions to decrease the prevalence of ABD in GM could include educating parents regarding the risks of earlier initiation of alcohol use, promoting the advantages of drinking alcohol with food rather than without, and addressing the belief among youths that binge drinking is a normal way to enjoy alcohol. Successful interventions could help to ease the future burden of direct and indirect consequences of alcohol use on the healthcare system and society. In conclusion, this study showed that binge drinking in adolescence is a prevalent problem that needs to be addressed using a multi-modal approach.
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10 CDC. Excessive alcohol use: addressing a leading risk for death, chronic disease and injury CDC; 2011. Available from: http://www.cdc.gov/chronicdisease/resources/ publications/aag/alcohol.htm (18 September 2014, date last accessed) 11 Svensson M. Alcohol use and social interactions among adolescents in Sweden: do peer effects exist within and/or between the majority population and immigrants? Soc Sci Med 2010;70:1858–64. 12 Morgenstern M, Isensee B, Sargent JD, et al. Exposure to alcohol advertising and teen drinking. Prevent Med 2011;52:146–51. 13 Reboussin BA, Song E-Y, Shrestha A, et al. A latent class analysis of underage problem drinking: evidence from a community sample of 16–20 year olds. Drug Alcohol Dependence 2006;83:199–209.
Acknowledgements
14 Wills TA, Sargent JD, Gibbons FX, et al. Movie exposure to alcohol cues and adolescent alcohol problems: a longitudinal analysis in a national sample. Psychol Addict Behav 2009;23:23–35.
We are grateful for the help provided by the EURO-URHIS and EURO-URHIS 2 project teams in each of the beneficiaries’
15 Patton GC, McMorris Bj Fau - Toumbourou JW, Toumbourou Jw Fau - Hemphill SA, et al. Puberty and the onset of substance use and abuse. (1098–4275 (Electronic)).
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16 van der Zwaluw CS, Kuntsche E Fau - Engels RCME, Engels RC. Risky alcohol use in adolescence: the role of genetics (DRD2, SLC6A4) and coping motives. (1530–0277 (Electronic)).
24 Wood MD, Read JP, Mitchell RE, et al. Do parents still matter? Parent and peer influences on alcohol involvement among recent high school graduates. Psychol Addict Behav 2004;18:19–30.
17 Windle M. Alcohol use among adolescents and young adults. Alcohol Res Health 2003;27:79–85.
25 Bahr SJ, Hoffmann JP, Yang X. Parental and peer influences on the risk of adolescent drug use. J Primary Prevent 2005;26:529–51.
18 Rostosky SS, Danner F, Riggle EDB. Is religiosity a protective factor against substance use in young adulthood? Only if you’re straight! J Adolesc Health 2007;40:440–7.
26 Reboussin BA, Preisser JS, Song E-Y, et al. Geographic clustering of underage drinking and the influence of community characteristics. Drug Alcohol Dependence 2010;106:38–47.
19 Llorens N, Barrio G, Sanchez A, et al. Effects of socialization and family factors on adolescent excessive drinking in Spain. Prevent Sci 2011;12:150–61.
27 Deas D. Adolescent substance abuse and psychiatric comorbidities. J Clin Psychiatry 2006;67:18–23.
20 Valios RF, Dunham AC, Jackson KL, et al. Association between employment and substance abuse behaviours among public high school students. J Adolesc Health 1999;25:256–63.
28 Pope D, Katreniak Z, Guha J, et al. Collecting standardised urban health indicator data at an individual level for school-aged children living in urban areas: methodology from EURO-URHIS 2. Eur J Public Health (In press).
21 Ellickson PL, Hays RD. Antecedents of drinking among young adolescents with different alcohol use histories. J Stud Alcohol 1991;52:398–408.
29 Chuang YC, Ennet ST, Bauman KE, et al. Neighbourhood influences on adolescent cigarette and alcohol use: mediating effects through parent and peer behavours. J Health Soc Behav 2005.
22 Piko BF, Kovacs E. Do parents and school matter? Protective factors for adolescent substance use. Addict Behav 2010;35:53–6. 23 Wilson N, Syme SL, Boyce WT, et al. Adolescent alcohol, tobacco, and marijuana use: the influence of neighborhood disorder and hope. Am J Health Promotion 2005;20:11–9.
30 Currie C, Roberts C, Morgan A, et al. Health Behaviour in School-aged Children (HBSC) study: international report from the 2001/2002 survey. Health Policy for Children and Adolescents, No. 4: World Health Organisation. Copenhagen, Denmark: WHO, 2004.
