What is evidence?


Many people talk about evidence – but what exactly does this term mean?


Generally, evidence is intended as any argument or “proof” in support of a conclusion or assertion. It can be seen as information that helps us prove or demonstrate truth – or disprove something that is false.


“Evidence is information in support of an assertion. That information can be strong or weak. We want that information to be as strong as possible.”

– Centre for Youth Impact


Evidence can come in many different forms, linked to different disciplines. There are many different types of evidence, from stories and testimony, to data from surveys or scientific trials. For public health interventions, including prevention science and practice, evidence refers to the effectiveness of an intervention in achieving certain outcomes that contribute to long lasting changes in the population health and behaviours.


Evidence can be “weak” or “strong”. There are different levels of value attached to different forms of evidence, different grades that identify good quality of evidence and that establish what counts as good evidence. That means drafting well-defined standards in order to classify the levels of evidence-based research.


Whatever form or level of evidence we need to describe, it is important to consider the audience for your evidence, and the use you want to make of it.


Why is evidence important?


Evidence is about accountability. Evidence is part of our everyday life and it helps us assess the impact and effectiveness of our work. When it comes to interventions for young people and children, evidence helps us to establish what types of programmes are more effective and can make a positive impact on the lives of our beneficiaries. Through evidence we can learn and improve our practice, increasing the value of our work for funders, commissioners, researchers and, most importantly, for the young people and the families we support.


How should evidence be used?


Using solid evidence can help us measure impact, better inform policy guidance and improve professional service delivery. Evidence should be used in the design, delivery and evaluation of programmes targeting young people.


Here are some important principles about using evidence:

  • Evidence is support, not proof or truth, of an assertion
  • Evidence provides a deeper understanding and insight into the impact of our work
  • Evidence gives us opportunities for reflection and improvement
  • Evidence is for anyone, adding value to all those involved in the delivery of, or benefitting from, services


Evidence-based practice in prevention


A well supported evidence-based intervention programme is usually comprised of two components: a strong magnitude of impact, along with a fair and rigorous methodological approach (Nation et al., 2003). In other words, there has to be causal relationship between implementation of the programme and outcomes of the intervention.


“Evidence-based practice” – meaning “best practice” or “with well-supported evidence” – is a crucial element in policy development and the implementation of programmes in the prevention field. When selecting prevention programmes for young people, policy makers, practitioners and health and education professionals need easy access to reliable and independently validated information.



Mentor advocates for programmes that have been proven by hard evidence to change young people’s attitudes and behaviour to alcohol and drugs and to (re)engage them in education, training volunteering and work.


Types of evidence-based prevention


We want a mix of evidence-based prevention which can have a real impact on young people’s lives:

  • Universal – Aimed at all children and young people, delivered through schools, youth clubs and/or families. Example: The Good Behaviour Game.
  • Targeted – For higher risk groups. Example: Families Together
  • Indicated – For young people showing early signs of substance abuse and other related problem behaviors associated with substance abuse. Example: Breaking Out.


The role of ADEPIS and CAYT


CAYT-ADEPIS largeThe Alcohol and Drug Education and Prevention Information Service (ADEPIS) is publicly acknowledged as the leading source of evidence-based information and tools for alcohol and drug education and prevention for schools and practitioners. The resources we have already produced draw on eight years of work with the Drug Education Forum, which supported local authorities and schools to implement best practice in drug education.


The Centre for Analysis of Youth Transitions (CAYT) houses a database of quality-assured studies that assess the impact of programmes and services supporting the development of young people; these may be delivered in a range of settings, including education settings. Mentor-ADEPIS took over the management of the repository in April 2015, and will be responsible for its development.


CAYT scoring system


CAYT’s primary aim is to provide education and prevention practitioners with evidence of what has proved – or is promising – to be of good practice; to highlight those programmes showing high effectiveness and rigorous evidence.



In 2015 we revised the original CAYT scoring system.


Click here to review the guidelines.