What is a cohort study?

The difference between cohort studies and randomised controlled trials, and what they can tell educators

A cohort study is a type of longitudinal study that follows participants who share a common characteristic over a period of time, often for many years.

The EEF view: what are the implications for education research?

A major benefit of cohort studies is that they allow us to look at a group of individuals from a year group, or generation, over a long period. They allow researchers to study lots of different outcomes at the same time, and generally produce multiple findings that can identify and draw attention to the specific issues being faced by the group being studied.

Because of their size, cohort studies can also help us find out how a major change - whether that’s a national policy or significant event - has affected specific groups within the population.

Unlike randomised controlled trials, it’s harder for cohort studies to give us the counterfactual: information about what would have happened to the group being studied otherwise. For example, a cohort study might tell us that young people who attended an early years setting are more likely to go on to university. But it’s more difficult for researchers to give us definitive answers about how those young people’s prospects would have been affected if they hadn’t accessed early years education.

Nevertheless, cohort studies can give us important information to help policymakers and education leaders target support.

Where can I see cohort studies in action?

The Sutton Trust and UCL Institute of Education’s Centre for Education Policy and Equalising Opportunities are running a major cohort study, with more than 12,000 young people, to find out the long-term impact of the pandemic on the education and employment outcomes of students who took their GCSEs in 2021, with a particular focus on disadvantaged groups.

The Millennium Cohort Study (MCS) - one of the biggest and most relevant cohort studies to education - regularly produces findings on a range of topics, including physical development, mental health and education attainment. A recent MCS report found that disadvantaged young people were more likely to struggle with their mental health over the summer holidays. This could help make sure that more support is available and signposted for those who might be vulnerable.

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