Twins Early Development Study (TEDS)

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The Twins Early Development Study aims to explore and gain greater understanding of how nature and nurture, our genes and our environment, influence learning abilities, cognitive abilities, and behaviour. In addition, the TEDS looks at how these abilities and behaviours relate to one another and change over time. The hope is that this research and the knowledge gained through it will go on to help us understand better the complexities of child and adolescent development and to inform and enable parents, teachers, policy makers and the general public to better manage and help with some of the challenges individuals face as they grow up.

Institute of Psychiatry, Psychology & Neuroscience (IoPPN), King's College London

Geographic coverage
United Kingdom - England & Wales

Start date


Sample type
Birth cohort - twin design

Sample details
Twins born in England and Wales between January 1994 and December 1996 were identified through birth records. Twins’ parents were contacted on behalf of TEDS by the UK Office for National Statistics after screening for infant mortality. 16,810 parents of twins responded that they were interested in participating in TEDS, with almost 14,000 families providing data at first contact. Considerable effort has been expended in recruiting and retaining families such as extensive follow ups, sending certificates of enrolment, gifts, hand-written birthday cards, a yearly newsletter and a freephone line. Each year information is sought about friends and close relatives in order to facilitate tracing families who move house which happens frequently for families of twins.

TEDS families are reasonably representative as compared to UK census data for families with children. 92% of mothers in the total TEDS sample are white, compared to 92% of UK mothers. The percentage of mothers with A-level exams is 32% for UK mothers and 34% for TEDS mothers. TEDS mothers are somewhat less likely to be working (41%) compared to all mothers in the UK (49%), which is likely to reflect difficulties with rearing twins.

Sample size at recruitment
13,694 families

Sample size at most recent sweep
Approx 4,300 families


Age at recruitment

Cohort year of birth


Data access
Data Request

Genetic data collected

Linkage to administrative data

Additional information


Related Themes
Administrative data, biomarkers, birth and perinatal period, cognitive measures, education, genetic data, language and literacy, personality measures, twin design, COVID

Reference paper

Haworth, CMA, Davis, OSP, Plomin, R (2013). Twins Early Development Study (TEDS): A Genetically Sensitive Investigation of Cognitive and Behavioral Development From Childhood to Young Adulthood. Twin Research & Human Genetics, 16, 117-125.

Medical Research Council
National Institutes of Health
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