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Prevention systems are harder to evaluate than single programmes, because what is being tested is a way of deciding, not a fixed intervention. The evidence for Communities That Care is nonetheless unusually strong for its kind: it rests on a randomised controlled trial with a twelve-year follow-up. It is also uneven across countries, and the most recent English-language review is cautious. This page presents both, because a reader who finds only the good news elsewhere will not trust it.
The Community Youth Development Study
The central trial began in 2003. Twenty-four small towns in seven US states were matched in pairs and one of each pair was randomly assigned to implement CTC. More than 4,400 young people were followed from the fifth grade, at around age ten, into early adulthood.
By the end of secondary school, young people in CTC towns were significantly less likely to have started using alcohol, tobacco or cannabis, and reported less delinquency and less violence. Because the trial was randomised, these differences can be attributed to CTC rather than to the kind of town that chooses to adopt it.
The effects lasted. At age 21, participants from CTC towns were 49 % more likely to have remained abstinent from so-called gateway drugs, 18 % more likely to have avoided antisocial behaviour altogether, and had an 11 % lower lifetime incidence of violence. By age 23 they were 20 % more likely to hold a university degree. Sustained tobacco abstinence was higher among young men.
The economic analysis followed the same participants. Five years in, benefits already exceeded costs. Over twelve years, each dollar invested in CTC returned 12.88 dollars in avoided harm, using conservative assumptions and primary outcomes only.
Australia
The first replication outside the United States was not a randomised trial. Toumbourou et al. (2019) compared the five localities of the first four Australian CTC coalitions with 104 comparison localities, using 41,328 adolescent surveys collected between 1999 and 2015. Lifetime alcohol use fell more steeply each year in the CTC localities (adjusted odds ratio 0.94, 95 % CI 0.93–0.95). The benefit-cost analysis of the same communities found a return of 2.60 Australian dollars per dollar invested, primarily from reduced alcohol-related harm. The effect was smaller than in the US trial, in a different policy environment, and it was positive.
Germany
CTC-EFF, a study led by the Hannover Medical School, examined the German implementation between 2020 and 2023 in 22 matched pairs of communities across four federal states. It was not a randomised trial, and most of its observation window fell into the pandemic. Two findings so far: CTC communities adopted more evidence-based programmes, from 3.57 to 8.57 per 10,000 residents, against a non-significant rise in the comparison communities (Decker et al., 2025), and the size of that effect depended on how well CTC was implemented (von Holt et al., 2025). On the broader system outcomes the study was designed around, the adoption of a science-based approach to prevention and cross-sector collaboration, no significant change was detectable by 2023 (Röding et al., 2026). Behavioural outcomes for young people are still being followed. It remains the most substantial European evaluation to date.
The Netherlands
The Netherlands has the longest European CTC tradition after the UK: the survey was adapted in 1999, and by the early 2010s more than 25 municipalities and neighbourhoods had run the process or at least its youth survey; most had stopped by the mid-2010s. The one controlled study, Jonkman et al. (2015), followed ten neighbourhoods in five cities, five with CTC and five without, from 2008 to 2011 and found no measurable effect on adolescent problem behaviour or on the initiation of drinking and smoking. The authors attribute the null result to threats to the internal validity of a community study of this kind rather than to the model, but it remains the clearest negative finding in Europe and belongs in any honest account.
The United Kingdom, and a cautious verdict
Communities that Care UK worked with more than sixty sites between 1998 and 2008; around thirty of them ran the CTC process, the rest commissioned the youth survey only. Operations ceased in 2009. The Joseph Rowntree Foundation's evaluation of three demonstration sites (Crow et al., 2004) found implementation uneven, the changes in risk and protective factors limited and not attributable to CTC with the design available, and the approach promising provided the implementation problems were solved. The programme ended when its funding did.
In November 2025 the Youth Endowment Fund, which advises on violence prevention in England and Wales, published a review of CTC in its Toolkit. Its meta-analysis of 41 effect sizes from 13 publications found a pooled relative risk of 0.93 across violence and offending outcomes, with a 95 % confidence interval of 0.84 to 1.02, which is not statistically significant, and substantial heterogeneity between studies. The Fund rated the approach as low impact, very low confidence and high cost, and advised: do not commission or scale new CtC programmes until further research demonstrates that the approach can be delivered effectively in the UK context.
Two things are worth knowing about that verdict. First, the review's own appendix records that none of the studies it pooled came from the United Kingdom; the concern is about deliverability in a setting where CTC has not run since 2009 and was last evaluated in the mid-2000s, not about the model. Second, the violence-only estimate of roughly 10 % less violence (relative risk 0.87, 95 % CI 0.75–1.01) is consistent with the direction of every other study on this page; what the review could not establish, on the studies available, was that the effect is reliably different from zero.
We think this is a fair challenge, and the right answer to it is European evidence rather than dismissal. Germany is generating it with CTC-EFF; Sweden, Estonia and Ireland are building the survey base for it, Ireland with a first baseline survey in 2026; Croatia contributes survey and implementation evidence.
What this adds up to
- In the one randomised trial with long follow-up, CTC reduced substance use, offending and violence, and the effects persisted into adulthood.
- Its economic return in that trial was large; in Australia it was positive and smaller.
- European evidence so far shows CTC communities adopting more evidence-based programmes, has not yet shown the wider system change the US trial found, and is thinner still on behavioural outcomes.
- The most recent independent review rates the effect on violence as uncertain, and the reason is a shortage of studies in the setting it cares about.
The literature library holds the 259 publications behind these summaries, in English, German, Portuguese and Spanish, each with a link to the original.