In this study we looked at the following questions: What are the trends in Dutch adolescents’ (aged 13–16) alcohol consumption, smoking behaviour and cannabis use between 2005 and 2009, in what groups are changes concentrated, and how is substance use clustered?

Our main finding is that in a period of only four years (2005–2009) a significant change in the prevalence of substance use among high school students has occurred among 13- to 16-year-old students with regard to all surveyed behaviours. Strongest decreases were found for alcohol use in last month, last month binge drinking and last month being drunk or tipsy and were found most prominent among 13-year-old students. These decreases were less with increase of age but were still significant among 16-year-olds. Similar reductions in alcohol consumption were found among boys and girls. In both educational levels the alcohol use between 2005 and 2009 decreased. The decreases in prevalence found for current binge drinking and being drunk or tipsy were stronger among students with a higher educational level. A significant decrease in cannabis use in the last month was found among girls and students with a high educational level. The decrease of lifetime cannabis use was significantly stronger among girls than boys. This may be explained by the relatively high cannabis use among the girls in 2005. In this study the decrease in smoking behaviour was significant among 13-year-old students, girls and students with a lower schooling level. Limitations to the interpretation of our results in being representative for the Dutch school-going population of 13- to 16-year-olds are (1) inclusion of only second and fourth year students in secondary school (2) the fact that in the study population we included more students in the higher than in the lower educational level compared with the overall high/low educational level ratio in the Netherlands, which was 46 %/54 % in 2005 and 50 %/50 % in 2009 [35].

Other Dutch study results are in line with our results; between 2003 and 2011 the lifetime and actual (last month) alcohol use strongly decreased among Dutch adolescents under 16: binge drinking decreased as well between 2003 and 2011 [17, 22, 23, 27, 35]. The decrease in last month drunkenness we found in our study was not shown in national studies [36]. Equally so, the decrease in cannabis use among girls in this study was not found in national studies and may therefore be a local characteristic [36]. Other Dutch studies did show decreasing trends in cannabis use (last year) among adolescents in the Netherlands between 2001 and 2009 [23]. Decreasing trends between 2001 and 2009 with regard to smoking [lifetime and daily] were also found in the national studies [23, 28]. Interestingly, we found that in 2005 smoking was still more common among girls, whereas in 2009 the gender-gap was no longer statistically significant. The latter was also found in other Dutch studies, and in several other western European countries [22, 23, 37].

To put those finding of decreasing trends of substance use in the Netherlands in perspective with other countries, the European School Survey Project on Alcohol and Drugs (ESPAD) reports are the best way to do this. ESPAD is carried out in 35 European countries, including 15- and 16-year-old students, with surveys in 1995, 1999, 2003, 2007 and 2011. ESPAD trend analyses between 2003 and 2011 showed that in the majority of countries last month alcohol use was unchanged between 2003 and 2007 and between 2007 and 2011 [38]. Between 2003 and 2007 ten countries reported significant decreases and two reported increases, between 2007 and 2011 nine countries reported significant decreases and four countries reported increases. The Nordic countries Iceland, Norway and Sweden, as well as Ireland and the Russian Federation (Moscow), showed decreases most consistent over time. Last month binge drinking was found to have increased in a large number of countries between 2003 and 2007 but showed a similar pattern as seen for last month drinking between 2007 and 2011 (nine report decreases and four report increases). Decreasing trends between 2007 and 2011 in last month cigarette smoking were seen in five countries, and a decreasing trend between 2007 and 2011 in last month cannabis use was seen in four. Taken together, decreasing trends of substance use among Dutch adolescents are not found in general in European countries.

A limitation of our study is that the cross-sectional nature of this study precludes any causal inference. The period between 2005 and 2009 has been a dynamic one, characterised by a major economic crisis, lower family incomes and increasing (job) insecurity. It is hard to attribute the general improvement in health and risk taking behaviour to any particular cause. However, the strong decrease between 2005 and 2009 in alcohol use among adolescents in high school parallels the national campaign that was started in 2006 and used the slogan ‘Not sixteen, not a drop’. The national campaign addressed adolescents and explicitly also parents [18]. Several studies support the idea that interventions addressing adolescents as well as their parents are effective in preventing alcohol use in early adolescents [24–27]. The question is whether the decrease of smoking and cannabis use which parallels the decrease in alcohol is some form of co-occurrence or whether it is due to parallel national anti-smoking prevention programmes, such as minor’s access law or smoking bans in public places [19, 39–42]. Clearly, this study provides evidence for the idea of co-occurrence because the clustering between multiple risk behaviours is strongly consistent over time also in relation to changing trends as was also shown by others [43]. Moreover, on the one hand, the dominancy and importance of targeting alcohol use in adolescents is supported by our results showing that adolescents who do not drink alcohol rarely use other substances and that this group has increased considerably between 2005 and 2009. On the other hand, although several studies showed that smoking and alcohol-drinking are strongly related [6, 43, 44], this and other national and international studies [22, 23, 43, 45] show that there is a group of adolescents who drink without smoking.

Another important finding is that, the campaign to reduce alcohol use, without there being a similarly important campaign to reduce cannabis use, has not lead to the one behaviour being replaced by the other. On the contrary, all unhealthy behaviours went down. Perhaps a common cause has influenced all behaviours simultaneously. For example, teaching parents the importance of influencing their children’s health choices in relation to alcohol might also have influenced the children’s behaviour with regard to cannabis use and smoking. This idea was also addressed in another study showing indeed that parental support and control (via the mediation of rules) were negatively associated with all adolescent risk behaviours (smoking, drinking and cannabis use), but on the other hand, parental rules that specifically targeted alcohol are strongly associated with drinking behaviour but not with smoking and cannabis use [30]. Also the latter study was a cross-sectional study. Longitudinal research is needed to study prevention programmes and the role of parents herewith in order to further investigate whether prevention on alcohol use can be sufficient in preventing not only alcohol use, but other risk behaviours such as tobacco and cannabis use simultaneously. However, it may also be possible that another common cause has influenced all behaviours simultaneously, such as the economic crisis.