Cannabis use and educational attainment

Jan van Ours, Jenny Williams

18 September 2007

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One of parents' greatest fears is that their child will become involved with drugs. Underlying this fear is the belief that drug use could lead to poor educational attainment, subsequent failure in the labour market, and without a good job to anchor their lives, an unhappy future. Viewed within a human capital framework, this scenario may find resonance. For example, drug use could lead teenagers to substitute time spent under the influence of drugs for time spent studying, resulting in poor academic achievement and an early exit from education. This is particularly a concern with cannabis because initiation into its use typically occurs during the teenage years, coinciding with the timing of critical decisions about investment in formal education, both at the extensive and intensive margins. There is, therefore, potential for youthful cannabis use to have a long-lasting effect through its impact on educational attainment.

In recent work, we investigated whether cannabis use leads to lower educational attainment (Van Ours and Williams, 2007b). Our research draws on information collected in the 2001 Australian National Drug Strategy Household Survey (NDSHS). In order to focus on people who can reasonably be considered to have completed their education, we limit our analysis to 25-50 years olds. Table 1 gives an overview of the cannabis use in this sample. As shown, more than half of the males and slightly less than half of the females indicate that they have used cannabis at some point in their lifetime. Of those who have used cannabis, 46% of males and 42% of females indicate that they first used cannabis by the age of 17.

Table 1. Prevalence of cannabis use (25-50 year olds)
Cannabis use ever Males Females
No 46.4 54.3
Yes 53.6 45.7
  100 100
If yes, starting age    
<15 17.5 18.0
16-17 28.4 24.2
18-25 47.9 50.1
>25 6.2 7.7
  100 100

This pattern of initiation is found in many countries. Most individuals start using cannabis between 15 and 25 years of age, with very few starting after the age of 25. Table 2 illustrates the relationship between cannabis use, age of initiation into cannabis and educational attainment, measured as “age of leaving formal education”.

Table 2. Cannabis use and age of leaving formal education (25-50 year olds)
Cannabis use Males Females
No 18.1 17.8
Yes, starting age    
<15 17.3 17.3
16-17 17.8 17.7
>18 18.1 18.4

Table 2 shows that, on average males who start using cannabis by the age of 15 complete 0.8 fewer years of education compared to those who never use cannabis. For females, the difference between the two groups is 0.5 year. Table 2 also shows that the older people are when they first use cannabis, the longer they remain in school.
These patterns are not unique to Australia. There is substantial evidence that early cannabis use is associated with lower levels of education. What is less well understood is the extent to which this association reflects the causal impact of cannabis use on education outcomes. For example, cannabis users may be more risk-loving or discount the future more heavily than non-users, and these attributes could also lead them to leave school early. In this case, the association between cannabis use and school-leaving is not casual because both behaviours are driven by people’s attitude to the future and to risk-taking. This scenario is referred to as selection on unobservables because attitudes to the future and risk-taking are not typically observed. Another explanation for the association between cannabis uptake and school-leaving is that young people who leave school early tend to have more free time and less adult supervision, and this provides greater opportunity for cannabis use. In this example, it is school-leaving that leads to cannabis use. This situation is referred to as reverse causality. The presence of either selection on unobservables or reverse causality (or both) acts as a confounder, so that the associations between initiation into cannabis use and educational attainment shown in Table 2 cannot be interpreted as reflecting cause and effect.

In our research, we use techniques which account for the potentially confounding effects discussed above in order to reliably estimate the impact of the age of initiation into cannabis use on educational attainment. We find that those who are initiated into cannabis use earliest suffer the greatest adverse effects in terms of educational attainment. For example, uptake of cannabis by the age of 15 reduces educational attainment in the range of 1.2 to 1.8 years for females and 0.3 to 0.8 of a year for males. We also find that initiation at older ages – for males after age 17 and for females after age 19 – seems to have no harmful effects on education.

Overall, our findings tend to suggest that parents are right to worry about their children's early use of cannabis, at least with respect to educational attainment. Early initiation into cannabis reduces educational attainment considerably. Traditional estimates of the rate of return to education imply that wages increase by 7-10% for every additional year of education. So a reduction in education due to early cannabis use is harmful to the individual because it reduces future earnings substantially. Furthermore, since employment prospects tend to be better for those with more education, future employment is also likely to be negatively affected by early cannabis use. Both earnings and employment effects are not only relevant for the individual (and their parents) but also the society as a whole. Having a greater number of workers with a low level of education imposes costs to society in terms of lower employment rates and growth potential.

So how urgent is this issue and what might policy makers do about it? The widespread use of cannabis amongst high-school students makes it an urgent matter. In the US, prevalence rates for lifetime cannabis use are around 32% for 10th graders and 42% for 12th graders (Johnston, et al. 2006). In Europe, prevalence rates amongst 17-18 year old high-school students ranges from 59% in France and 49% in Italy to 15% in Greece and Sweden (Andersson et al, 2007). This suggests that in some countries, up to one half of youths may be leaving formal education early because of their cannabis use. While the policy implications of studies into the consequences of drug use are often less than straightforward (Godfrey, 2006), we think that the implications from our study are very clear. They suggest that (1) preventing cannabis uptake will improve the educational outcomes of youths, and (2) even if cannabis use cannot be prevented, delaying the age at which uptake occurs will deliver educational benefits. But how can this be achieved? Despite a significant quantity of research into the determinants of initiation into drug use, the uptake process remains poorly understood (Bretteville-Jensen, 2006). Previous studies do, however, provide evidence that the prevalence of cannabis use in general may be reduced by policies that raise its price (Van Ours and Williams, 2007), and that the prevalence of cannabis use in schools can be reduced by school-based informational campaigns on the risks associated with cannabis consumption (Duarte et al.,2006).

References

Andersson, B., Hibell, B., Beck, F., Choquet, M., Kokkevi, A., Fotiou, A., Molinaro, S., Nociar, A., Sieroslawski, J.,and Trapencieris, M. (2007) Alcohol and Drug Use Among European 17-18 Year Old Students, Data from the ESPAD Project. The Swedish Council for Information on Alcohol and Other Drugs (CAN) and the Pompidou Group at the Council of Europe. Stockholm: Sweden.Bretteville-Jensen, A.L. (2006) Drug Demand -- Initiation, Continuation and Quitting, De Economist, 154, 491-516.

Duarte, R., Escario, J.J. and Molina, J.A. (2006) Marijuana Consumption and School Failure among Spanish Students, Economics of Education Review, 25, 472-481.

Johnston, L. D., O'Malley, P.M., Bachman, J. G. and Schulenberg, J. E. (2006) Teen Drug Use Continues Down in 2006, Particularly Among Older Teens. University of Michigan New and
Information Services: Ann Arbour,MI [On-Line] Available:www.monitoringthefuture.org; accessed 18 August 2007.

Van Ours, J.C. and Williams, J. (2007a) Cannabis Prices and Dynamics of Cannabis Use, Journal of Health Economics, 26, 578-596.

Van Ours, J.C. and Williams, J. (2007b) Why Parents Worry: Initiation into Cannabis Use by Youth and their Educational Attainment, CEPR Discussion Paper, No. 6449.

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Topics:  Education

Tags:  education, cannabis

Professor in Labour Economics, Tilburg University; Professorial Fellow at the Department of Economics, University of Melbourne; CEPR Research Fellow

Professor in the Department of Economics, University of Melbourne

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