Does Marriage Moderate Genetic Effects on Delinquency and Violence?

• Author: Hexuan Liu,Yi Li,Guang Guo
• Date: 01 October 2015
• DOI: http://doi.org/10.1111/jomf.12208
• Published date: 01 October 2015

Y L University of North Carolina at Chapel Hill

H L University of North Carolina at Chapel Hill∗

G G University of North Carolina at Chapel Hill∗∗

Does Marriage Moderate Genetic Effects

on Delinquency and Violence?

Using data from the National Longitudinal Study

of Adolescent to Adult Health (N=1,254), the

authors investigated whether marriage can fos-

ter desistance from delinquency and violence by

moderating genetic effects. In contrast to exist-

ing gene–environment research that typically

focuses on one or a few genetic polymorphisms,

they extended a recently developed mixed lin-

ear model to consider the collective inuence

of 580 single nucleotide polymorphisms in 64

genes related to aggression and risky behav-

ior. The mixed linear model estimates the pro-

portion of variance in the phenotype that is

explained by the single nucleotide polymor-

phisms. The authors found that the proportion of

variance in delinquency/violence explained was

smaller among married individuals than unmar-

ried individuals. Because selection, confound-

ing, and heterogeneity may bias the estimate of

Department of Sociology, 155 Hamilton Hall, Universityof

North Carolina, Chapel Hill, NC 27599 (yili@live.unc.edu).

∗Department of Sociology and Carolina Population Center,

206 W. Franklin St., University of North Carolina, Chapel

Hill, NC 27599.

∗∗Department of Sociology, Carolina Population Center,

and Carolina Center for Genome Sciences, 206 W. Franklin

St., University of North Carolina, Chapel Hill, NC 27599.

This article was edited by Robert Crosnoe.

Key Words: aggression, marriage, National Longitudi-

nal Study of Adolescent to Adult Health (Add Health),

youth/emergent adulthood.

the Gene ×Marriage interaction, theyconducted

a series of analyses to address these issues.

The ndings suggest that the Gene ×Marriage

interaction results werenot seriously affected by

these issues.

The impact of marriage on individuals’

well-being has long been studied. Married

individuals exhibit higher levels of healthy

behaviors, survival probability, wages, and so

forth than unmarried individuals (Waite, 1995).

Of particular interest has been the inhibiting

effect of marriage on antisocial behavior such

as delinquency and crime. Researchers have

found that the transition to marriage is linked to

a decline in antisocial behavior. This desistance

effect of marriage has been noted in multiple

cohorts (King, Massoglia, & Macmillan, 2007;

Sampson & Laub, 1993) and in different coun-

tries (Blokland & Nieuwbeerta, 2005; Theobald

& Farrington, 2009).

In recent years, researchers have increasingly

incorporated genetic variables into their exam-

inations of the effects of social environments

on antisocial behavior (e.g., Caspi et al., 2002).

The ndings that social factors interact with

genes to inuence antisocial behavior under-

line the importance of gene–environment inter-

action (G×E, a term that refers to processes

wherein genetic inuences depend on environ-

mental factors or vice versa). But existing G ×E

research almost exclusively focuses on one or

Journal of Marriage and Family 77 (October 2015): 1217–1233 1217

DOI:10.1111/jomf.12208

1218 Journal of Marriage and Family

a few genetic variants. Unlike rare Mendelian

traits that are determined by a single gene or

allele, overall genetic inuence on antisocial

behavior comprises a large number of genetic

effects (Anholt & Mackay, 2012). Therefore, it

is essential to examine more than a few genetic

variants in G ×E research on antisocial behavior.

In this study, we extended previous G×E

research by considering a large number of

genetic variants. Drawing on data from the

National Longitudinal Study of Adolescent to

Adult Health (Add Health; see http://www.cpc.

unc.edu/projects/addhealth), we examined

whether marriage moderates the collective

inuence of 580 single nucleotide polymor-

phisms (SNPs) in 64 genes on delinquency and

violence. To do so we used a recently devel-

oped mixed linear model implemented in the

genome-wide complex traits analysis (GCTA)

software (Yang, Lee, Goddard, & Visscher,

2011). This new method estimates a heritability

parameter: the proportion of variance in the

phenotype that is jointly explained by the SNPs.

We examined the Gene×Marriage interaction

by comparing the proportion of variance in anti-

social behavior explained by 580 SNPs among

married and unmarried individuals. The samples

in the mixed linear models were drawn from the

Add Health genetic subsample. Our approach

might be implemented using larger data in the

future. Selection, confounding, and heterogene-

ity can bias the estimate of the Gene ×Marriage

interaction. We conducted a series of analyses

to address these issues.

B

Marriage and Antisocial Behavior

Social scientists have long noticed that marriage

is an important life course transition with seem-

ingly far-reaching impact. In general, married

individuals consider marriage a long-term con-

tract (Waite, 1995). To maintain the contract,

they tend to do things that pay off in the long run,

and they refrain from behaviors that bring instant

gratication or the possibility of harmful conse-

quences. This idea is supported by research nd-

ings indicating that marriage may deter criminal

activity and deviant behavior (e.g., Blokland &

Nieuwbeerta, 2005; Farrington & West, 1995;

Horney, Osgood, & Marshall, 1995; Sampson &

Laub, 1993; Warr, 1998).

The effect of marriage on antisocial behav-

ior may be thought of as the result of three

processes. First, marriage may strengthen con-

nections within the family. Married couples are

connected to each other in relationships for

which there are strong social norms. Married

people tend to fulll the normative expecta-

tions implied by marriage. On the basis of

social control theory (Hirschi, 1969), Sampson,

Laub, and colleagues have focused on bonds

and ties created within marriage (Laub, Nagin,

& Sampson, 1998; Laub & Sampson, 2003;

Sampson & Laub, 1993; Sampson, Laub, &

Wimer, 2006). This line of research proposes

that marriage establishes strong bonds and ties

that prevent individuals from committing crime

over the life course. Interpersonal attachment to

a partner serves as a control mechanism. Over

time, individuals invest more and more social

and nancial resources in a marriage. Engag-

ing in criminal activity is not a rational choice

because it threatens that investment. Summariz-

ing their position, Sampson and Laub (1993)

stated that marriage creates “interdependent sys-

tems of obligation and constraints that impose

signicant costs for translating criminal propen-

sities into action” (p. 141).

Second, marriage may weaken connections

outside of the family that might lead to antisocial

behavior. Peer inuence can be a major source

of variation in antisocial behavior (Osgood,

Wilson, O’Malley, Bachman, & Johnston,

1996). The transition to marriage usually means

that routine activities are primarily devoted to

the spouse and family. Warr (1998) showed that

marriage may weaken or disrupt connections

with peers, including delinquent ones. After the

transition to marriage, time spent with peers

decreases dramatically. As a result, opportu-

nities and motivations to engage in crime and

delinquency are signicantly limited. Warr

found that these changes largely account for

the association between marriage and antisocial

behavior. In addition, the obligations that come

with marriage tend to leave less time for leisure

activities outside of the family (Osgood & Lee,

1993); therefore, unstructured socializing with

delinquent peers may also be limited.

Third, marriage may lead to changes at the

psychological level and, by extension,alter one’s

perception of antisocial behavior. Because mar-

riage implies meaningful commitment, married

persons may develop a sense of obligation to

their partners that reduces the appeal of behav-

iors that might threaten the relationship. Cog-

nitive and identity transformations are at work