This page refers to the current evidence on the effectiveness of the available prevention interventions for school students. Information on the methodology used and the definition of terms can be found on the methodology page.
Date of last update: 11.05.2012. Next update: March 2013.
Summary: School based interventions based on social influence and/or on skill-based interventions have been proven to be effective in reducing licit and illicit drug use; interventions aimed at disadvantaged students and interventions peer-lead have shown promising results.
School-based programmes that implement the concepts of social influence and life skills were found to be effective in:
School-based interactive programmes (i.e. those involving discussion) implemented in schools with predominantly special population, were found in a meta-analysis of 207 studies (Tobler et al., 2000), in a re-analyses of the same set of studies (Roona et al., 2003) and in a further analysis of 15 studies (N = 15.571 sampling units) (Porath-Waller et al., 2010), to be more effective than non-interactive programmes (i.e. a lecture) in:
A review of 29 reviews (McGrath et al., 2006) found evidence in favour of the effectiveness of peer educators in school-based drug prevention programmes in:
However, this relative effectiveness did not extend to 1 or 2 year follow-ups (McGrath et al., 2006).
Affective-focused programs, compared to usual curricula and knowledge-focused interventions were found in a systematic review of 32 studies (29 RCTs and three CPSs, N= 46539) (Faggiano et al, 2005), to be effective in improving:
No interventions met the criteria for this category.
A review of 29 reviews (McGrath et al., 2006) found evidence that booster sessions or similar extra components that aimed to reinforce the effects of a programme have a positive impact on the pre-specified outcomes. However, since the relationship between booster sessions and programme outcomes was not statistically examined, the link should be treated as hypothetical.
There is little evidence that interventions with multiple components are more effective than interventions with single components as shown in a systematic review (Foxcroft et al., 2011b):
School-based generic prevention programs (not including life/social skills approaches, see above in the Beneficial category) have not shown enough evidence to be effective in a systematic review (Foxcroft et al., 2011a) of 53 RCTs in:
Life skills programmes were found to be no more effective than usual curricula (Faggiano et al., 2005) in:
Knowledge focused programs were examined in a meta-analysis (Faggiano et al, 2005) and were found:
There is evidence from a narrative review including results of one RCT (N=326) (Velleman 2009) that specific training given to young people in order to make them influence each other is not effective in:
No interventions met the criteria for this category.
Below you can find definitions and further explanation for some of the terms used in this section of the Best practice portal. A more general glossary for the best practice portal is also available.
A type of prevention intervention which aims to they aim to modify inner qualities (personality traits such as self-esteem and self-efficacy, and motivational aspects such as the intention to use drugs).
Before-after (BA) study design
Interventions for which precise measures of the effects in favour of the type of intervention were found in systematic reviews of relevant studies. An intervention ranked as ‘beneficial’ is suitable for most patients/contexts. See the relevant module methodology page for further information.
Controlled before-after (CBA) study design. UCBA stands for Uncontrolled before-after study design.
Cognitive behavioral therapy is an individual based intervention occurring in three stages. Phase 1 is aimed at determining and prioritizing the patient’s problems and constructing the treatment contract. Phase 2 is aimed at increasing coping competence and reducing risky behaviors. Phase 3 focuses on relapse prevention. Each session is administered once per week over a period of 4-6 months with 60- to 90-minute sessions (Beck AT, Wright FW, Newman CF, Liese B. Cognitive Therapy of substance abuse. New York: Guilford Press, 1993).
Controlled clinical trials (CCT)
A cohort study is a type of observational study that follows a group of people (i.e. a cohort) over time. In a prospective cohort study, the cohort is formed and then followed over time. In a retrospective cohort study, data is gathered for a cohort that was formed sometime in the past.
The Confidence Interval (CI) is a measure of the precision (or uncertainty) of study results. It is the interval that most likely includes the true value of the parameter we are calculating, where 'most likely' is taken by common usage to be a 95% probability. Thus the current expression of '95 % CI'. A wide CI indicates less precise estimates of effect and vice versa.
Current population survey (CPS)
A cross-sectional study is a study employing a single point of data collection for each participant or system being studied.They are usually conducted to estimate the prevalence of the outcome of interest for a given population at a given point in time.
Interventions that gave negative results if compared with a standard intervention or no intervention, for example. See the relevant module methodology page for further information.
Additional information for prevention
For ethical reasons this category in prevention should be considered as interventions with negative and undesired (iatrogenic) effect.
Individual psychotherapy is a standard individual treatment based on counseling and motivational interviewing and focused on substance use triggers and strategies for relapse prevention. It includes elements of cognitive-behavioral therapy (CBT).
Intermittent time series design (CPS)
Knowledge-focused prevention intervention
A type of prevention intervention which aims to to enhance knowledge of drugs, and drug effects, and consequences.
Interventions that were shown to have limited measures of effect, that are likely to be effective but for which evidence is limited. An intervention ranked as ‘likely to be beneficial’ is suitable for most contexts/patients, with some discretion. See the relevant module methodology page for further information.
The Number Needed to Treat (NNT)indicates the number of patients that needs to be treated to obtain one respondent patient. Numerically the NNT is the reciprocal of the difference between the proportion of events in the experimental and the comparison group (absolute risk reduction). Taking into consideration that the ideal NNT would be 1 (the unreal situation in which every single patient succeeded) it is easily understood that a NNT value close to 3 or 4 would be very good.
The Adjusted Odds Ratio is a way of comparing whether the probability of a certain event is the same between two groups, yet they are calculated adjusting for or controlling for other possible contributions from other variables (tipically demographic variables) in the model. An AOR equal to 1 implies that the the event is equally probable in both groups. An AOR greater than 1 implies that the event is more likely in the first group. An AOR less than 1 implies that the event is less likely in the first group.
The Odds Ratio is a way of comparing whether the probability of a certain event is the same between two groups. Like the Relative Risk, an OR equal to 1 implies that the the event is equally probable in both groups. A OR greater than 1 implies that the event is more likely in the first group. A OR less than 1 implies that the event is less likely in the first group. In medical research, the odds ratio is commonly used for case-control studies, as odds, but not probabilities, are usually estimated. Relative risk is used in randomized controlled trials and cohort studies.
A p-value is a measure of how much evidence we have against the null hypothesis. The null hypothesis represents the hypothesis of no change or no effect. The smaller the p-value, the more evidence we have against the null hypothesis thus it is more likely that our sample result is true. Traditionally, researchers will reject a null hypothesis if the p-value is less than 0.05.
Randomised controlled trial (RCT)
The Relative Risk (RR) is used to compare the risk in the two different groups of people, i.e. treated and control groups to see if belonging to one group or another increases or decreases the risk of developing certain outcomes. This measure of effect will tell us the number of times an outcome is more likely (RR > 1) or less likely (RR < 1) to happen in the treatment group compared with the control group.
Interventions that obtained measures of effects in favour of the intervention, but that showed some limitations or unintended effects that need to be assessed before providing them. See the relevant module methodology page for further information.
Interventions for which there are not enough studies or where available studies are of low quality (with few patients or with uncertain methodological rigour), making it difficult to assess if they are effective or not. Interventions for which more research should be undertaken are also grouped in this category.
Additional information for prevention
For prevention interventions, this is also known as 'zero effect'.
A type of prevention intervention which aims to enhance students’ abilities in generic skills, refusal skills and safety skills.
The Standardised Mean Difference (SMD) is the difference in means divided by a standard deviation. Note that it is not the standard error of the difference in means (a common confusion). The standardized mean difference has the important property that its value does not depend on the measurement scale. It may be useful if there are several trials assessing the same outcome, but using different scales.
The z-score (aka, a standard score) indicates how many standard deviations an element is from the mean of the population.
According to recent European surveys (1), on average, 23 % of boys and 17 % of girls have tried illicit drugs at least once during their lifetime . The term ‘any illicit drug’ includes cannabis, amphetamines, cocaine, crack, ecstasy, LSD and heroin. Reported use of illicit drugs varies considerably across the countries (ESPAD 2007). Prevention targeting schools offer a systematic and efficient way of reaching large numbers of young people.
(1) The European school survey project on alcohol and other drugs (ESPAD) uses standardised methods and instruments to measure drug and alcohol use among representative samples of 15- to 16-year-old school students. Surveys have been conducted in 1995, 1999, 2003 and 2007.
In 2007, data were collected in 35 countries, including 25 EU Member States, Norway and Croatia (AR 2010).
Since adolescence is per se a risk factor, and the majority of illicit drug users start to use at this age, school is an efficient setting for universal prevention. Moreover, within the larger target group of school youth there are particularly vulnerable sub-groups including early school leavers and students with social or academic problems (as well as young offenders, young people in institutional care, young people living in neighbourhoods where multiple risk factors and problems associated with drug use are concentrated). Overlaps between these groups may exist. For example, children with poor school attendance or poor academic performance may also be experiencing other problems such as problems in the family or juvenile crime. Furthermore, there may be cumulative effects of belonging to more than one vulnerability category, which may be associated with an even greater likelihood of drug use.
School programs can be designed to provide knowledge about the effects of drugs on the body and psychological effects, as a way of building negative attitudes toward drugs; to build individual self-esteem and self-awareness, working on psychological factors that may place people at risk of use; to teach refusal and social life skills; to change perception of prevalence (or informal norms); and to encourage alternative activities to drug use, which instil control abilities.
Interventions for school students can be classified into the following groups:
Also interventions with family- or community-based components were included in this section, provided the school-based component was predominant.
The main aim of prevention interventions delivered to school children is to deter or to delay the onset of substance use by providing all individuals with the information and skills necessary to prevent the problem.
Studies usually consider also the outcomes related to knowledge and /or awareness of drugs risks, however these outcomes are surrogate ones which means that there are no proofs that awareness/knowledge has impact on use. In absence of a clear relation between awareness/knowledge and outcomes on use, we decided NOT to consider them.