Does marriage inhibit antisocial behavior?: An examination of selection vs causation via a longitudinal twin design.
BACKGROUND
Previous studies have indicated that marriage is negatively associated with male antisocial behavior. Although often interpreted as a causal association, marriage is not a random event. As such, the association may stem from selection processes, whereby men less inclined toward antisocial behavior are more likely to marry.


OBJECTIVE
To evaluate selection vs causation explanations of the association between marriage and desistence from antisocial behavior.


METHODS
Co-twin control analyses in a prospective twin study provided an analogue of the idealized counterfactual model of causation. The co-twin control design uses the unmarried co-twin of a married twin to estimate what the married twin would have looked like had he remained unmarried. Discordant monozygotic (MZ) twins are particularly informative because they share a common genotype and rearing environment.


METHODS
General community study.


METHODS
Two hundred eighty-nine male-male twin pairs (65.1% MZ) from the Minnesota Twin Family Study underwent assessment at 17, 20, 24, and 29 years of age. None of the participants were married at 17 years of age, and 2.6% were married at 20 years of age. By 29 years of age, 58.8% of the participants were or had been married.


METHODS
A tally of criterion C symptoms of DSM-III-R antisocial personality disorder, as assessed via structured clinical interview.


RESULTS
Mean differences in antisocial behavior across marital status at age 29 years were present even at 17 and 20 years of age, suggesting a selection process. However, the within-pair effect of marriage was significant for MZ twins, such that the married twin engaged in less antisocial behavior following marriage than his unmarried co-twin. Results were equivalent to those in dizygotic twins and persisted when controlling for prior antisocial behavior.


CONCLUSIONS
Results indicate an initial selection effect, whereby men with lower levels of antisocial behavior are more likely to marry. However, this tendency to refrain from antisocial behavior appears to be accentuated by the state of marriage.
Department of Psychology, Michigan State University, East Lansing, 48824, USA. burts@msu.edu
S Alexandra
SA
Burt
M Brent
MB
Donnellan
Mikhila N
MN
Humbad
Brian M
BM
Hicks
Matt
M
McGue
William G
WG
Iacono
D000293:Adolescent; D000328:Adult; D000987:Antisocial Personality Disorder / Q000453:epidemiology* / Q000235:genetics* / Q000523:psychology; D039721:Diagnostic and Statistical Manual of Mental Disorders; D004200:Diseases in Twins / Q000453:epidemiology* / Q000235:genetics; D005260:Female; D006801:Humans; D008297:Male; D008393:Marriage / Q000523:psychology* / Q000706:statistics & numerical data*; D008910:Minnesota / Q000453:epidemiology; D011446:Prospective Studies; D012919:Social Behavior; D012931:Social Environment; D014427:Twins / Q000235:genetics / Q000523:psychology*; D014429:Twins, Dizygotic / Q000523:psychology; D014430:Twins, Monozygotic / Q000523:psychology; D055815:Young Adult