ArticleBMJ (Clinical research ed.)2005
The cognitive cost of being a twin: evidence from comparisons within families in the Aberdeen children of the 1950s cohort study.
Article in BMJ (Clinical research ed.), 2005. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 17 papers, 2 of them syntheses that pooled it.
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Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.
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Who cites it
17 citing papers in PubMed, 2 syntheses or guidelines pooled it.
- Heritability of Psychological Traits and Developmental Milestones in Infancy: A Systematic Review and Meta-analysis.JAMA network open · 2022Pooled it
- Neurodevelopmental Outcomes of Twins Compared With Singleton Children: A Systematic Review.Twin research and human genetics : the official journal of the International Society for Twin Studies · 2018Pooled it
- Twins and their singleton siblings differ in language, cognition, and social-emotional development.Child development · 2026Article
- Neurodevelopmental outcome of preterm twins at 5 years of age.Pediatric research · 2020Article
- Prenatal and perinatal risks for late language emergence in a population-level sample of twins at age 2.BMC pediatrics · 2018Article
- Prenatal fish oil supplementation and early childhood development in the Upstate KIDS Study.Journal of developmental origins of health and disease · 2017Observational
- An Observational Study to Evaluate Associations Between Low-Level Gestational Exposure to Organophosphate Pesticides and Cognition During Early Childhood.American journal of epidemiology · 2016Observational
- Cognitive Functioning after Surgery in Middle-aged and Elderly Danish Twins.Anesthesiology · 2016Article
- Article
- Is the Web as good as the lab? Comparable performance from Web and lab in cognitive/perceptual experiments.Psychonomic bulletin & review · 2012Article
- Twin-singleton differences in neonatal brain structure.Twin research and human genetics : the official journal of the International Society for Twin Studies · 2011Article
- The effect of an increase in the rate of multiple births on low-birth-weight and preterm deliveries during 1975-2008.Journal of epidemiology · 2010Article
- Academic achievement of twins and singletons in early adulthood: Taiwanese cohort study.BMJ (Clinical research ed.) · 2008Article
- Evidence for a two-stage model of dependence using the NESARC and its implications for genetic association studies.Drug and alcohol dependence · 2008Article
- Educational performance in twins.BMJ (Clinical research ed.) · 2006Article
- Comparison of academic performance of twins and singletons in adolescence: follow-up study.BMJ (Clinical research ed.) · 2006Article
- The Predictive Value of Developmental Assessments at 1 and 2 for Intelligence Quotients at 6.IntelligenceArticle
Corrections and comments
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Authors and funding
3 authors.
Funding
No grant is acknowledged in the PubMed record.
Abstract
objectivesTo determine whether twins have lower IQ scores in childhood than singletons in the same family and, if so, whether differences in fetal growth explain this deficit.
designCohort study.
settingScotland.
participants9832 singletons and 236 twins born in Aberdeen between 1950 and 1956.
resultsAt age 7, the mean IQ score of twins was 5.3 points lower (95% confidence interval 1.5 to 9.1) and at age 9, 6.0 points lower (1.7 to 10.2) than that of singletons in the same family. Adjustment for sex, mother's age, and number of older siblings had little effect on these differences. Further adjustment for birth weight and gestational age attenuated the IQ difference between twins and singletons: the difference in mean IQ was 2.6 points (-1.5 to 6.7) at age 7 and 4.1 points (-0.5 to 8.8) at age 9.
conclusionsTwins have substantially lower IQ in childhood than singletons in the same family. This effect cannot be explained by confounding due to socioeconomic, maternal, or other family characteristics, or by recruitment bias. The reduced prenatal growth and shorter gestations of twins may explain an important part of their lower IQ in childhood.
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