Extended Twin Kinship Designs

Limitations of Twin Studies

• Limited to “ACE” model• No test of assumptions of twin design• C biased by assortative mating, passive rGE,

stratification• C and D tend to cancel• Cannot separate components of C: vertical cultural

inheritance, extra-familial shared environment, special C in twins, parent-child interaction

• Twin pairs are same age

Extending the Phenotype

Me

World Parents

Siblings

Child

Spouse

Extended Phenotype

Extending Twin Kinships

Extensions: Design

• Twins and Parents (TAP)• Longitudinal Twins and Parents (LTAP)• Children of Twins (COT)• Spouses of Twins (SPOT)• Siblings of Twins • The Full Monty: Extended Twin Kinship Design

E.T. (AKA “Stealth”, “Cascade”).

Extensions: Assessment

• MEASURE THE ENVIRONMENT• MEASURE THE GENOTYPE• MEASURE THE ENDOPHENOTYPE AND

EPIGENOME• DYADIC ASSESSMENT (interactions of relative

pairs).

Some else’s model may not suit your problem

Be creative!!!

Parents of Twins

• Anticipate “adult outcome” of child phenotype (quick and dirty developmental study)

• Provide environment for offspring (parent-child interaction)

• Spousal resemblance• Clue to non-additive genetic effects

Siblings of Twins

• “Are twins special? Funny? Different?”• Sibling interaction effects, confluence, density,

family size (also non-twin singletons)• Age-moderation of family resemblance (are

different genes/environments expressed at different ages – GxAge interaction).

Children of Twins

• Resolve effects of maternal and offspring genotype on offspring behavior

• Resolve genetic and non-genetic components of parent-child resemblance

The Virginia 30,000

Unpacking Assortative Mating

Phenotypic Assortment

Assortment for Latent Trait

Social Homogamy

Spousal Intersaction

The mediating effect of parental neglect on adolescent and young

adult anti-sociality: A longitudinal study of twins

and their parents (LTAP).

Lindon Eaves, Liz Prom, Judy Silberg

Parental ASP and Child Neglect/Adversity

So: Does neglect cause childhood antisocial

behavior (“environmentally”)?

OR

Is it a result of the fact that neglect is an expression of (genetic?) anti-social behavior in

the parents?

OR BOTH.

Conceptual Model

Initial Model for Genetic Effects

Polychoric correlations between anti-social behavior of (adult) parents and adult and juvenile anti-social behavior of their offspring.

Twin correlations

Model comparison

Genetic effects of assortment andPassive rGE

Significant assortment doesn’t do much genetically (here)Not much passive rGE even though parental ASP geneticand affects child’s environment

Non-genetic transmission

Unique and Shared Environment

Children of Twins (COT)

Unraveling the effect of genes and environment in the transmission of parental

antisocial behavior to children’s conduct disturbance, depression, and hyperactivity.

Judy Silberg, Hermine Maes, Lindon Eaves