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Hart SA, Schatschneider C. Genetics can inform causation, but the concepts and language we use matters. Behav Brain Sci 2023; 46:e191. [PMID: 37694911 PMCID: PMC10953348 DOI: 10.1017/s0140525x22002175] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/12/2023]
Abstract
Madole & Harden describe how genetics can be used in a causal framework. We agree with many of their opinions but argue that comparing within-family designs to experiments is unnecessary and that the proposed influence of genetics on behavior can be better described as inus conditions.
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Affiliation(s)
- Sara A Hart
- Department of Psychology, Florida State University, Tallahassee, FL, USA www.idcdlab.com
- Florida Center for Reading Research, Florida State University, Tallahassee, FL, USA
| | - Christopher Schatschneider
- Department of Psychology, Florida State University, Tallahassee, FL, USA www.idcdlab.com
- Florida Center for Reading Research, Florida State University, Tallahassee, FL, USA
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Louca P, Mompeo O, Leeming ER, Berry SE, Mangino M, Spector TD, Padmanabhan S, Menni C. Dietary Influence on Systolic and Diastolic Blood Pressure in the TwinsUK Cohort. Nutrients 2020; 12:E2130. [PMID: 32708992 PMCID: PMC7400881 DOI: 10.3390/nu12072130] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Revised: 07/08/2020] [Accepted: 07/15/2020] [Indexed: 02/07/2023] Open
Abstract
Nutrition plays a key role in blood pressure (BP) regulation. Here, we examine associations between nutrient intakes and BP in a large predominantly female population-based cohort. We assessed the correlation between 45 nutrients (from food frequency questionnaires) and systolic BP/diastolic BP (SBP/DBP) in 3889 individuals from TwinsUK not on hypertensive treatments and replicated in an independent subset of monozygotic twins discordant for nutrient intake (17-242 pairs). Results from both analyses were meta-analysed. For significant nutrients, we calculated heritability using structural equation modelling. We identified and replicated 15 nutrients associated with SBP, 9 also being associated with DBP, adjusting for covariates and multiple testing. 14 of those had a heritable component (h2: 27.1-57.6%). Strong associations with SBP were observed for riboflavin (Beta(SE) = -1.49(0.38), P = 1.00 × 10-4) and tryptophan (-0.31(0.01), P = 5 × 10-4), while with DBP for alcohol (0.05(0.07), P = 1.00 × 10-4) and lactose (-0.05(0.0), P = 1.3 × 10-3). Two multivariable nutrient scores, combining independently SBP/DBP-associated nutrients, explained 22% of the variance in SBP and 13.6% of the variance in DBP. Moreover, bivariate heritability analysis suggested that nutrients and BP share some genetic influences. We confirm current understanding and extend the panel of dietary nutrients implicated in BP regulation underscoring the value of nutrient focused dietary research in preventing and managing hypertension.
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Affiliation(s)
- Panayiotis Louca
- Department of Twin Research, King’s College London, St Thomas’ Hospital Campus, Westminster Bridge Road, London SE1 7EH, UK; (P.L.); (O.M.); (E.R.L.); (M.M.); (T.D.S.)
| | - Olatz Mompeo
- Department of Twin Research, King’s College London, St Thomas’ Hospital Campus, Westminster Bridge Road, London SE1 7EH, UK; (P.L.); (O.M.); (E.R.L.); (M.M.); (T.D.S.)
| | - Emily R. Leeming
- Department of Twin Research, King’s College London, St Thomas’ Hospital Campus, Westminster Bridge Road, London SE1 7EH, UK; (P.L.); (O.M.); (E.R.L.); (M.M.); (T.D.S.)
| | - Sarah E. Berry
- Department of Nutritional Sciences, King’s College London, London WC2R 2LS, UK;
| | - Massimo Mangino
- Department of Twin Research, King’s College London, St Thomas’ Hospital Campus, Westminster Bridge Road, London SE1 7EH, UK; (P.L.); (O.M.); (E.R.L.); (M.M.); (T.D.S.)
- NIHR Biomedical Research Centre at Guy’s and St Thomas’ Foundation Trust, London SE1 9RT, UK
| | - Tim D. Spector
- Department of Twin Research, King’s College London, St Thomas’ Hospital Campus, Westminster Bridge Road, London SE1 7EH, UK; (P.L.); (O.M.); (E.R.L.); (M.M.); (T.D.S.)
| | - Sandosh Padmanabhan
- Institute of Cardiovascular & Medical Sciences, University of Glasgow, Glasgow G12 8QQ, UK;
| | - Cristina Menni
- Department of Twin Research, King’s College London, St Thomas’ Hospital Campus, Westminster Bridge Road, London SE1 7EH, UK; (P.L.); (O.M.); (E.R.L.); (M.M.); (T.D.S.)
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Arafat S, Minică CC. Fetal Origins of Mental Disorders? An Answer Based on Mendelian Randomization. Twin Res Hum Genet 2018; 21:485-494. [PMID: 30587273 PMCID: PMC6390405 DOI: 10.1017/thg.2018.65] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2018] [Accepted: 11/08/2018] [Indexed: 01/10/2023]
Abstract
The Barker hypothesis states that low birth weight (BW) is associated with higher risk of adult onset diseases, including mental disorders like schizophrenia, major depressive disorder (MDD), and attention deficit hyperactivity disorder (ADHD). The main criticism of this hypothesis is that evidence for it comes from observational studies. Specifically, observational evidence does not suffice for inferring causality, because the associations might reflect the effects of confounders. Mendelian randomization (MR) - a novel method that tests causality on the basis of genetic data - creates the unprecedented opportunity to probe the causality in the association between BW and mental disorders in observation studies. We used MR and summary statistics from recent large genome-wide association studies to test whether the association between BW and MDD, schizophrenia and ADHD is causal. We employed the inverse variance weighted (IVW) method in conjunction with several other approaches that are robust to possible assumption violations. MR-Egger was used to rule out horizontal pleiotropy. IVW showed that the association between BW and MDD, schizophrenia and ADHD is not causal (all p > .05). The results of all the other MR methods were similar and highly consistent. MR-Egger provided no evidence for pleiotropic effects biasing the estimates of the effects of BW on MDD (intercept = -0.004, SE = 0.005, p = .372), schizophrenia (intercept = 0.003, SE = 0.01, p = .769), or ADHD (intercept = 0.009, SE = 0.01, p = .357). Based on the current evidence, we refute the Barker hypothesis concerning the fetal origins of adult mental disorders. The discrepancy between our results and the results from observational studies may be explained by the effects of confounders in the observational studies, or by the existence of a small causal effect not detected in our study due to weak instruments. Our power analyses suggested that the upper bound for a potential causal effect of BW on mental disorders would likely not exceed an odds ratio of 1.2.
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Affiliation(s)
- Subhi Arafat
- Department of Biological Psychology, Vrije Universiteit, Amsterdam, the Netherlands
| | - Camelia C. Minică
- Department of Biological Psychology, Vrije Universiteit, Amsterdam, the Netherlands
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Haworth CMA, Nelson SK, Layous K, Carter K, Jacobs Bao K, Lyubomirsky S, Plomin R. Stability and Change in Genetic and Environmental Influences on Well-Being in Response to an Intervention. PLoS One 2016; 11:e0155538. [PMID: 27227410 PMCID: PMC4881940 DOI: 10.1371/journal.pone.0155538] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2015] [Accepted: 04/29/2016] [Indexed: 12/03/2022] Open
Abstract
Genetic and environmental influences on complex traits can change in response to developmental and environmental contexts. Here we explore the impact of a positive activity intervention on the genetic and environmental influences on well-being and mental health in a sample of 750 adolescent twins. Twins completed a 10-week online well-being intervention, consisting of kindness and gratitude tasks and matched control activities. The results showed significant improvements both in well-being and in internalizing symptoms in response to the intervention activities. We used multivariate twin analyses of repeated measures, tracking stability and change in genetic and environmental influences, to assess the impact of this environmental intervention on these variance components. The heritability of well-being remained high both before and after the intervention, and the same genetic effects were important at each stage, even as well-being increased. The overall magnitude of environmental influences was also stable across the intervention; however, different non-shared environmental influences emerged during the intervention. Our study highlights the value of exploring the innovations in non-shared environmental influences that could provide clues to the mechanisms behind improvements in well-being. The findings also emphasize that even traits strongly influenced by genetics, like well-being, are subject to change in response to environmental interventions.
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Affiliation(s)
- Claire M. A. Haworth
- MRC Integrative Epidemiology Unit, School of Experimental Psychology & School of Social and Community Medicine, University of Bristol, Bristol, United Kingdom
| | - S. Katherine Nelson
- Department of Psychology, Sewanee: The University of the South, Sewanee, United States of America
| | - Kristin Layous
- Department of Psychology, University of California Riverside, Riverside, United States of America
| | - Kathryn Carter
- Social, Genetic and Developmental Psychiatry Centre, King’s College London, London, United Kingdom
| | - Katherine Jacobs Bao
- Department of Psychology, University of California Riverside, Riverside, United States of America
| | - Sonja Lyubomirsky
- Department of Psychology, University of California Riverside, Riverside, United States of America
| | - Robert Plomin
- Social, Genetic and Developmental Psychiatry Centre, King’s College London, London, United Kingdom
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Olson RK, Keenan JM, Byrne B, Samuelsson S. Why do Children Differ in Their Development of Reading and Related Skills? SCIENTIFIC STUDIES OF READING : THE OFFICIAL JOURNAL OF THE SOCIETY FOR THE SCIENTIFIC STUDY OF READING 2014; 18:38-54. [PMID: 25104901 PMCID: PMC4120985 DOI: 10.1080/10888438.2013.800521] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Modern behavior-genetic studies of twins in the U.S., Australia, Scandinavia, and the U.K. show that genes account for most of the variance in children's reading ability by the end of the first year of formal reading instruction. Strong genetic influence continues across the grades, though the relevant genes vary for reading words and comprehending text, and some of the genetic influence comes through a gene - environment correlation. Strong genetic influences do not diminish the importance of the environment for reading development in the population and for helping struggling readers, but they question setting the same minimal performance criterion for all children.
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Affiliation(s)
- Richard K Olson
- Department of Psychology and Neuroscience, and Institute for Behavioral Genetics, University of Colorado Boulder, and Department of Behavioral Sciences and Learning, Linköping University
| | | | - Brian Byrne
- School of Behavioural, Cognitive and Social Sciences, University of New England, and Department of Behavioral Sciences and Learning, Linköping University
| | - Stefan Samuelsson
- Department of Behavioral Sciences and Learning, Linköping University
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Harlaar N, Trzaskowski M, Dale PS, Plomin R. Word reading fluency: role of genome-wide single-nucleotide polymorphisms in developmental stability and correlations with print exposure. Child Dev 2014; 85:1190-1205. [PMID: 24392801 PMCID: PMC4064251 DOI: 10.1111/cdev.12207] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The genetic effects on individual differences in reading development were examined using genome-wide complex trait analysis (GCTA) in a twin sample. In unrelated individuals (one twin per pair, n = 2,942), the GCTA-based heritability of reading fluency was ~20%-29% at ages 7 and 12. GCTA bivariate results showed that the phenotypic stability of reading fluency from 7 to 12 years (r = 0.69) is largely driven by genetic stability (genetic r = 0.69). Genetic effects on print exposure at age 12 were moderate (~26%) and correlated with those influencing reading fluency at 12 (genetic r = 0.89), indicative of a gene-environment correlation. These findings were largely consistent with quantitative genetic twin analyses that used both twins in each pair (n = 1,066-1,409).
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Abstract
The Florida State Twin Registry began in 2002 through a pilot study of personality disorders and executive cognitive functioning in adult twins. Since 2006, the registry has grown substantially as part of the Learning Disability Research Center at Florida State University that recently began its second funding cycle through the National Institute of Child Health and Development. An update on the Florida State Twin Registry sample, focus, and measures is provided, as well as future directions.
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