Rural environments reduce the genetic influence on adolescent substance use and rule-breaking behavior.
BACKGROUND
There is increasing evidence that certain environmental factors can modify genetic effects. This is an important area of investigation as such work will help to guide the development of new intervention programs. In this paper, we address whether rural environments moderate the genetic influence on adolescent substance use and rule-breaking behavior (i.e. externalizing psychopathology).


METHODS
Over 1200 Minnesotan 17-year-old twins were classified as either urban or rural. Externalizing behavior was operationalized as the use and abuse of alcohol and drugs along with symptoms of conduct, oppositional defiant, and antisocial personality disorders. Biometric factor modeling estimated whether the relative contribution of genetic and shared environmental factors varied from urban to rural settings.


RESULTS
Residency effects reached statistical significance in the male sample only. In urban environments, externalizing behavior was substantially influenced by genetic factors, but in rural environments, shared environmental factors became more influential. This was apparent at both the individual-variable and factor levels.


CONCLUSIONS
These findings suggest a gene-environment interaction in the development of male adolescents' problem behaviors, including substance use. The results fit within an expanding literature demonstrating both the contextual nature of the heritability statistic and how certain environments may constrain the expression of genetic tendencies.
Legrand
L N
LN
Department of Psychology, University of Minnesota, Twin Cities Campus, Minneapolis, MN 55455, USA. legra002@umn.edu
Keyes
M
M
McGue
M
M
Iacono
W G
WG
Krueger
R F
RF
D000293:Adolescent; D000294:Adolescent Behavior / Q000523:psychology*; D000987:Antisocial Personality Disorder / Q000453:epidemiology / Q000235:genetics / Q000523:psychology; D019958:Attention Deficit and Disruptive Behavior Disorders / Q000453:epidemiology / Q000235:genetics / Q000523:psychology; D001699:Biometry / Q000379:methods; D019955:Conduct Disorder / Q000453:epidemiology / Q000235:genetics / Q000523:psychology; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D007389:Internal-External Control; D007604:Juvenile Delinquency / Q000523:psychology* / Q000706:statistics & numerical data*; D008297:Male; D008910:Minnesota / Q000453:epidemiology; D012424:Rural Population / Q000706:statistics & numerical data*; D017678:Sex Distribution; D012931:Social Environment; D019966:Substance-Related Disorders / Q000453:epidemiology* / Q000235:genetics / Q000523:psychology; D014505:Urban Population / Q000706:statistics & numerical data