Peer substance involvement modifies genetic influences on regular substance involvement in young women.
OBJECTIVE
Peer substance involvement (PSI) is a robust correlate of adolescent substance use. A small number of genetically informative studies suggest that shared genetic and environmental factors contribute to this association. We examine mechanisms by which PSI influences the etiology of regular substance involvement (RSI), particularly in women.


METHODS
Population-based cohort study of twin women from the US Midwest.


METHODS
2176 twin women.


METHODS
To examine the relationship between self-reported PSI during adolescence and a composite RSI representing regular tobacco, alcohol and cannabis use during young adulthood, using genetically informative correlation, moderation and joint correlation-moderation models.


RESULTS
There was evidence for a significant additive genetic X environment interaction. PSI was moderately heritable (h(2) = 0.25). Genetic, shared and non-shared influences on RSI overlapped with influences on PSI (genetic correlation of 0.43). Even after controlling for these shared genetic influences, RSI was more heritable in those reporting greater PSI.


CONCLUSIONS
While young women may select peers based on certain dispositional traits (e.g. permissiveness towards substance use), the social milieu constructed by PSI does modify the architecture of increased RSI in those individuals with increasing levels of PSI being associated with stronger expression of heritable influences.
Agrawal
Arpana
A
Washington University School of Medicine, Department of Psychiatry, St Louis, MO 63110, USA. arpana@wustl.edu
Balasubramanian
Sumitra
S
Smith
Emily K
EK
Madden
Pamela A F
PA
Bucholz
Kathleen K
KK
Heath
Andrew C
AC
Lynskey
Michael T
MT
D000293:Adolescent; D000294:Adolescent Behavior / Q000523:psychology; D000328:Adult; D000428:Alcohol Drinking / Q000453:epidemiology / Q000235:genetics* / Q000523:psychology; D004200:Diseases in Twins; D004812:Epidemiologic Methods; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D008385:Marijuana Smoking / Q000453:epidemiology / Q000235:genetics / Q000523:psychology; D010379:Peer Group; D012907:Smoking / Q000453:epidemiology / Q000235:genetics* / Q000523:psychology; D012931:Social Environment; D013223:Statistics as Topic; D019966:Substance-Related Disorders / Q000453:epidemiology / Q000235:genetics* / Q000523:psychology; D014481:United States / Q000453:epidemiology; D055815:Young Adult