The role of the Children of Twins design in elucidating causal relations between parent characteristics and child outcomes

Abstract

An assessment of the strengths and limitations of the Children of Twins design and a comparison with other research strategies suggest that the design plays a unique role in the study of developmental psychology and psychopathology. Finally, the authors describe how methodological advances and future applications of the design will provide additional insight into the causal processes underlying children's adjustment to environmental stimuli.

Smoking during pregnancy and offspring externalizing problems: An exploration of genetic and environmental confounds

“…Overall, associations between SDP and offspring externalizing behaviors have remained significant in most of the extant SDP studies when the measured covariates are included in the analyses (Cnattingius, 2004;Wakschlag, Pickett, Cook, Benowitz, & Leventhal, 2002). Some parental variables, however, such as ongoing exposure to secondhand smoke (Maughan, Taylor, Taylor, Butler, & Bynner, 2001), maternal report of conduct disorder as a teenager (but not adult externalizing problems) (Silberg et al, 2003), and antisocial behavior of both parents (Maughan, Taylor, Caspi, & Moffitt, 2004), mediate a majority of the relation between SDP and CP.In addition to the numerous potential environmental risk factors associated with SDP, a number of researchers have noted that genetic confounds may mediate the relationship between SDP and offspring externalizing problems (D'Onofrio et al, 2003;Fergusson, 1999;Moffitt, 2005;Silberg et al, 2003;Wakschlag, Pickett, Cook, Benowitz, & Leventhal, 2002). Mothers who smoke during pregnancy may pass down genetic risk for externalizing problems to their offspring, a form of passive gene-environment correlation (rGE; Scarr & McCartney, 1983).…”

“…Similarly, SEMs estimated the variance attributable to additive genetic factors (V a ) to be zero. Moreoever, the intergenerational parameter associated with genetic variance (b a ) was unstable (i.e., b a was large but had very large SEs), a result that frequently occurs when one latent variance component is negligible (D'Onofrio et al, 2003).Therefore, the parameters associated with genetic factors (V a and b a ) were constrained to be zero in the subsequent models., making the SEMs a between and within-level of SDP at the nuclear family and NLSY household levels. The subsequent SEMs included all adult sibling pairs, including those in the NLSY where the genetic relatedness of the siblings was unknown.…”

“…In addition to the numerous potential environmental risk factors associated with SDP, a number of researchers have noted that genetic confounds may mediate the relationship between SDP and offspring externalizing problems (D'Onofrio et al, 2003;Fergusson, 1999;Moffitt, 2005;Silberg et al, 2003;Wakschlag, Pickett, Cook, Benowitz, & Leventhal, 2002). Mothers who smoke during pregnancy may pass down genetic risk for externalizing problems to their offspring, a form of passive gene-environment correlation (rGE; Scarr & McCartney, 1983).…”

“…Genetic risk for antisocial behavior may contribute to a mother's likelihood of SDP and may confer vulnerability to externalizing problems when inherited by offspring. Standard correlational research approaches, in which environmental and genetic risks are confounded, are ineffective in delineating whether associations between externalizing problems and SDP are due to environmental causation or passive rGE (D'Onofrio et al, 2003;Moffitt, 2005;Rutter, Pickles, Murray, & Eaves, 2001). Moreover, most of the genetically informed studies of SDP and externalizing problems in offspring (Button, Thapar, & McGuffin, 2005;Knopik et al, 2005;Maughan, Taylor, Caspi, & Moffitt, 2004;Thapar et al, 2003) have used an approach, including a measure of SDP in a standard twin study, that assumes the relation is purely environmental (Purcell & Koenen, 2005;Turkheimer, D'Onofrio, Maes, & Eaves, 2005).…”

A Genetically Informed Study of Marital Instability and Its Association With Offspring Psychopathology.

“…However, Meyer et al (2000) reported that the statistical association between marital discord and adolescent conduct problems was mediated by shared genetic factors related to conduct problems in both generations. Extended twin-family studies are able to test both causal and selection processes, but the design includes several major methodological assumptions and restrictions that limit the interpretability and generalizability of the results (D'Onofrio et al, 2003;Rutter et al, 2001). …”