Using Twins to Assess What Might Have Been: The Co-twin Control Design

Dijk, Wilhelmina van; Norris, Cynthia U.; Hart, Sara A.

doi:10.1177/10497315221120604

Cited by 5 publications

(4 citation statements)

References 30 publications

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“…We agree with the authors that viewing genetic causality as probabilistic, instead of deterministic, is a fruitful way to view the effects of genetics on behavior. Moreover, we agree that using within-family designs will strengthen our understanding of the causal effects of genetics on development (Hart, Taylor, & Schatschneider, 2013; van Dijk, Norris, & Hart, in press). However, there are two points we wish to discuss from Madole & Harden (M&H).…”

supporting

confidence: 57%

Genetics can inform causation, but the concepts and language we use matters

Hart,

Schatschneider

2023

Behav Brain Sci

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supporting

confidence: 57%

Genetics can inform causation, but the concepts and language we use matters

Hart,

Schatschneider

2023

Behav Brain Sci

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“…The STAGE survey includes a validated short-form inventory with 11 questions [55] and the variable was handled as continuous. Symptoms of burnout was measured using a validated short form of Pines Burnout Measure [56], including three questions regarding symptoms 70 [58] 87 [48] 2059 [24] 514 [38] 1545 [22] Lower level of neuroticism 6579 [75] 147 [48] 51 [42] 96 [52] 6432 [76] 854 [62] 5578 [78] Table 1 (continued) of burnout, which has been shown to correlate strongly with the full Pines Burnout Measure [57]. Ratings were made along a 7-point scale ranging from 1 (never) to 7 (all the time), providing a total score ranging from 3 to 21.…”

Section: Covariatesmentioning

confidence: 99%

“…To assess the impact of any familial factors on the association between work-related violence/threats or harassment/bullying and sickness absence due to CMDs, co-twin control analyses using conditional logistic regression were performed [48]. Only complete pairs of MZ and same-sex DZ twins who were discordant (i.e., different) in terms of the exposure of interest were included.…”

Section: Statistical Analysesmentioning

confidence: 99%

“…This twin study, which was performed with a co-twin control design, sometimes referred to as discordant twin pair design, takes advantage of the fact that monozygotic twin pairs in general share 100% of their genes, while dizygotic twins share on average 50% of the genes, and both types of twins share the same early environment when reared together [47]. Consequently, the unexposed twin serves as a nearly perfect control to the exposed twin [48]. The fact that the twins are matched both on shared environmental and genetic backgrounds is a major strength and makes it possible to control for these potential confounding factors that otherwise may not be possible.…”

Section: Introductionmentioning

confidence: 99%

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The role of familial factors and neuroticism in the association between exposure to offensive behaviors at work and long-term sickness absence due to common mental disorders - a prospective twin study

Wijkander,

Svedberg,

Narusyte

et al. 2024

BMC Public Health

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Objectives The aim of this study was to investigate associations between exposure to work-related violence/threats and harassment, and future sickness absence (SA) due to common mental disorders (CMDs), taking familial factors (shared genetics and early-life environment) and neuroticism into account. Methods The study sample included 8795 twin individuals from the Swedish Twin Project of Disability Pension and Sickness Absence (STODS), including survey data from the Study of Twin Adults: Genes and Environment (STAGE). Self-reported work-related violence and/or threats as well as work-related harassment (including bullying) and national register data on SA due to CMDs were analyzed using standard logistic regression, and conditional logistic regression among complete twin pairs discordant on exposures. Individuals were followed for a maximum of 13 years. Interactions between neuroticism and exposures were assessed using both multiplicative and additive interaction analyses. Results Exposure to work-related violence/threats was associated with higher odds of SA due to CMDs when adjusting for age, sex, marital status, children, education, type of living area, work characteristics, and symptoms of depression and burnout (OR 2.11, 95% CI 1.52–2.95). Higher odds of SA due to CMDs were also found for exposure to harassment (OR 1.52, 95% CI 1.10–2.11) and a combined indicator of exposure to violence/threats and/or harassment (OR 1.98, 95% CI 1.52–2.59), compared with the unexposed. Analyses of twins discordant on exposure, using the unexposed co-twin as reference, showed reduced ORs. These ORs were still elevated but no longer statistically significant, potentially due to a lack of statistical power. No multiplicative interaction was found between neuroticism and exposure to work-related violence/threats, or harassment. However, a statistically significant additive interaction was found between neuroticism and exposure to violence/threats, indicating higher odds of SA due to CMDs in the group scoring lower on neuroticism. Conclusions Exposure to work-related offensive behaviors was associated with SA due to CMDs. However, the results indicated that these associations may be partly confounded by familial factors. In addition, an interaction between exposure and neuroticism was suggested. Thus, when possible, future studies investigating associations and causality between offensive behaviors at work and mental health-related outcomes, should consider familial factors and neuroticism.

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Familial confounding or measurement error? How to interpret findings from sibling and co-twin control studies

Gustavson,

Torvik,

Davey Smith

et al. 2024

Eur J Epidemiol

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Epidemiological researchers often examine associations between risk factors and health outcomes in non-experimental designs. Observed associations may be causal or confounded by unmeasured factors. Sibling and co-twin control studies account for familial confounding by comparing exposure levels among siblings (or twins). If the exposure-outcome association is causal, the siblings should also differ regarding the outcome. However, such studies may sometimes introduce more bias than they alleviate. Measurement error in the exposure may bias results and lead to erroneous conclusions that truly causal exposure-outcome associations are confounded by familial factors. The current study used Monte Carlo simulations to examine bias due to measurement error in sibling control models when the observed exposure-outcome association is truly causal. The results showed that decreasing exposure reliability and increasing sibling-correlations in the exposure led to deflated exposure-outcome associations and inflated associations between the family mean of the exposure and the outcome. The risk of falsely concluding that causal associations were confounded was high in many situations. For example, when exposure reliability was 0.7 and the observed sibling-correlation was r = 0.4, about 30–90% of the samples (n = 2,000) provided results supporting a false conclusion of confounding, depending on how p-values were interpreted as evidence for a family effect on the outcome. The current results have practical importance for epidemiological researchers conducting or reviewing sibling and co-twin control studies and may improve our understanding of observed associations between risk factors and health outcomes. We have developed an app (SibSim) providing simulations of many situations not presented in this paper.

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Using Twins to Assess What Might Have Been: The Co-twin Control Design

Cited by 5 publications

References 30 publications

Genetics can inform causation, but the concepts and language we use matters

Genetics can inform causation, but the concepts and language we use matters

The role of familial factors and neuroticism in the association between exposure to offensive behaviors at work and long-term sickness absence due to common mental disorders - a prospective twin study

Familial confounding or measurement error? How to interpret findings from sibling and co-twin control studies

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