Enviromental & Family Influence

Johnson, W., McGue, M. & Iacono, W.G. (2006) Genetic and Environmental Influences on Academic Achievement Trajectories during Adolescence. Developmental Psychology, 42, 514-532.

Herndon, R.W., McGue, M., Krueger, R.F. & Iacono, W.G. (2005). Genetic and Environmental Influences on Adolescents’ Perceptions of Current Family Environment. Behavior Genetics, 35, 373-380.

King, S.M., Burt, A., Malone, S.M., McGue, M. & Iacono, W.G. (2005). Etiological Contributions to Heavy Drinking from Late Adolescents to Young Adulthood. Journal of Abnormal Psychology, 114, 587-598.

The authors examined genetic and environmental contributions to stability and change in heavy drinking from late adolescence to young adulthood in a sample of 1,152 twin pairs. In men, heavy drinking was similarly heritable at ages 17 (h2 _ .57) and 20 (h2 _ .39), and its stability owed primarily to common genetic factors. In women, heavy drinking was less heritable than in men at ages 17 (h2 _ .18) and 20 (h2 _ .30) and its stability was primarily due to enduring shared environmental influences. P3 amplitude, an event-related brain potential marker of alcoholism risk, was less predictive of heavy drinking in women than in men, providing further support for the proposition that biological factors have less impact on heavy drinking in young adult women than in young adult men.

Freivalds, S. (2004). Nature and Nurture: A new look at how families work. Families by Law: A Adoption Reader (pp. 85-87) New York and London: New York University Press.

Walden, B., McGue, M., Iacono, W. G., Burt, A. & Elkins I. (2004). Identifying Shared Environmental Contributions to Early Substance Use: The Respective Roles of Peers and Parents. Journal of Abnormal Psychology, 113, 440-450.
Although behavior genetic studies have suggested that early substance use is primarily environmentally mediated, no study has sought to identify the specific sources of environmental variance. Using data obtained from multiple informants, this study assessed the contributions of peer deviance and parent–child relationship problems to substance use in 14-year-old male and female twins (N _ 1,403) drawn from the Minnesota Twin Family Study (MTFS). All three phenotypes were influenced primarily by shared environmental variance (average c2 _ .51), as was the overlap among them. Moreover, peer deviance and parent– child relationship problems accounted for approximately 77% of the variance in early substance use. Findings also indicated that peer deviance, but not parent– child relationship problems, accounted uniquely for variance in early substance use.

Klump, K. L., M. McGue, et al. (2000). "Age differences in genetic and environmental influences on eating attitudes and behaviors in preadolescent and adolescent female twins." Journal of Abnormal Psychology 109(2): 239-251.
This study made use of MTFS 11-year-old and 17-year-old females to examine age differences in genetic and environmental influences on eating disordered behaviors and attitudes and associations between body mass index and eating disorders.  Shared environmental influences on both the eating disorders and their associations with body mass index were more important for 11-year-olds, while genetic influences were more important for 17-year-olds.  Still, for the older twins, most of the genetic influences on eating disorders were independent of the genetic associations with body mass index.

Shiner, R. L. and N. R. Marmorstein (1998). "Family environments of adolescents with lifetime depression: associations with maternal depression history." J Am Acad Child Adolesc Psychiatry 37(11): 1152-60.
To assess family functioning of adolescents with a history of depression, taking into account maternal history of depression. METHOD: Lifetime major depression was assessed with standardized interviews in an epidemiological sample of adolescent twins and their parents. Family members completed questionnaires measuring family functioning. The families of three groups of adolescents were compared: ever-depressed adolescents with ever-depressed mothers (n = 37), ever- depressed adolescents with never-depressed mothers (n = 42), and never- depressed control adolescents (n = 82). RESULTS: A greater proportion of ever-depressed adolescents had ever-depressed mothers than did control adolescents (47% versus 18%); rates of paternal depression did not differ between the two groups. Ever-depressed adolescents with ever- depressed mothers described poorer family functioning than did ever- depressed adolescents with never-depressed mothers and controls. Relative to control mothers, mothers of both groups of ever-depressed adolescents reported family difficulties, particularly in the father- adolescent relationship. Fathers' descriptions of family relationships did not differ among the three groups. Ever-depressed adolescents came disproportionately from divorced families. CONCLUSIONS: These results highlight the importance of considering parental depression in the treatment of adolescent depression and underscore the need to understand the interactional patterns in families of depressed youth, particularly those with multiple depressed members.

Elkins, I. J., M. McGue, et al. (1997). "Genetic and environmental influences on parent-son relationships: evidence for increasing genetic influence during adolescence." Dev Psychol 33(2): 351-63.
Genetic and environmental influences on self-reported parent-child relationships were examined in a sample of 824 individual male twins and their parents. Cross-sectional comparisons of twin similarity at ages 11 and 17 were undertaken to identify developmental changes in the contribution of genetic and environmental factors to family relationships. Significant genetic influences were found on perceptions of parent-son conflict, regard, involvement, and overall support. Heritabilities were significantly higher in older twins, suggesting increased genetic influence with age. Age differences were present primarily in the father-son relationship. These results provide support for the proposal of S. Scarr and K. McCartney (1983) that the importance of active gene-environment correlations increases during adolescence. Older adolescents may have more choice and impact on the nature of the relationships they have with their parents.

Billig, J. P., S. L. Hershberger, et al. (1996). "Life events and personality in late adolescence: genetic and environmental relations." Behavior Genetics 26(6): 543-54.
The relationship between life events and personality was investigated in the Minnesota Twin/Family Study, using 216 monozygotic and 114 dizygotic 17-year-old male twin pairs. Participants completed a life events interview designed for adolescents and the Multidimensional Personality Questionnaire. Life events were categorized into three types: life events to which all members of a family would be subject and those affecting an individual, which can be broadly construed as either nonindependent or independent. Univariate genetic model fitting indicated the presence of significant genetic effects (h2 = 49%) for nonindependent nonfamily life events but not for the other two types of life events. Bivariate genetic model fitting further confirmed that the significant phenotypic correlation between nonindependent life events and personality is in part genetically mediated. Specifically, the findings suggest that genetically influenced individual differences in constraint play a substantial role in life events whose occurrence is not independent of the individual's behavior.



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