Anderson, K.N., Lee, R.M., Rueter, M.A., & Kim, O.M. (2015). Associations between discussions of racial and ethnic differences in internationally adoptive families and delinquent behavior among Korean adopted adolescents. Children and Youth Services Review, 51, 66-73. PMCID: PMC4341837

Abstract: Internationally adopted adolescents may have more delinquent behavior than non-adopted adolescents. One explanation is these adolescents experience discrimination and loss of culture, and adoptive parents are not adequately addressing these experiences. However, studies have not examined the effects of family discussions of racial and ethnic differences within adoptive families on adopted adolescents' delinquent behavior. To test this relationship, this study utilized data from 111 U.S. internationally adoptive families with 185 South Korean adopted adolescents (55% female, M age = 17.75). During an observational assessment, families discussed the importance of their racial and ethnic differences, and adolescents completed a delinquent behavior questionnaire. Analysis of covariance showed differences in adolescent delinquent behavior across three ways adoptive families discussed racial and ethnic differences; adolescents whose families acknowledged differences had the fewest mean delinquent behaviors. There were no significant differences in delinquent behavior between adolescents whose families acknowledged or rejected the importance of racial and ethnic differences. However, adopted adolescents whose families held discrepant views of differences had significantly more problem behavior than adolescents whose families either acknowledged or rejected the importance of racial and ethnic differences. Clinicians, adoption professionals, and other parenting specialists should focus on building cohesive family identities about racial and ethnic differences, as discrepant views of differences are associated with the most adoptee delinquent behavior.

Garcia, S.E., Tully, E.C., Tarantino, N., South, S., Iacono W.G., & McGue M.(2013). Changes in genetic and environmental influences on trait anxiety from middle adolescence to early adulthood. Journal of Affective Disorders, 151(1), 46-53. PMCID: PMC3769500

Results: The heritability of trait anxiety increased with age, particularly between ages 14 and 18, no significant new genetic influences emerged after age 14, and the genetic influences were highly correlated across the three ages, supporting developmentally stable genetic risk factors. The environmental effects shared by members of a family decreased in influence across adolescence, while the influence of environmental effects unique to each individual twin remained relatively stable over the course of development and were largely age-specific
Limitations: The twin study design does not inform about specific genes and environmental risk factors.
Conclusions: Genetic influences increased in importance from middle to late adolescence but common genetic factors influenced trait anxiety across the three ages. Shared environmental influences decreased in importance and demonstrated negligible influence by late adolescence/early adulthood. Nonshared environmental effects were almost entirely age-specific. These findings support the importance of developmentally-sensitive interventions that target shared environmental factors prior to middle adolescence and shifting non-shared environmental risks at each age.

Kim, O., Reichwald, R., & Lee, R. (2012). Cultural socialization in families with adopted korean adolescents: A mixed-method, multi-informant study. Journal of Adolescent Research, 28(1), 69-95. doi: 10.1177/0743558411432636. PMCID: PMC3825402

Abstract: Transracial, transnational families understand and transmit cultural socialization messages in ways that differ from same-race families. This study explored the ways in which transracial, transnational adoptive families discuss race and ethnicity and how these family discussions compared to self-reports from adoptive parents and adolescents regarding the level of parental engagement in cultural socialization. Of the thirty families with at least one adolescent-aged child (60% female, average age 17.8 years) who was adopted from South Korea, nine families acknowledged racial and ethnic differences, six families rejected racial and ethnic differences, and fifteen families held a discrepancy of views. Parents also reported significantly greater engagement in cultural socialization than adolescents' reports of parental engagement. However, only adolescent self-reports of parental engagement in cultural socialization matched the qualitative coding of family conversations.

Smith, A., Ribeiro, J., Mikolajewski, A., Taylor, J., Joiner, T., Iacono, W. (2012). An examination of environmental and genetic contributions to the determinants of suicidal behavior among male twins. Psychiatry Research,197(2012), 60-65. PMCID: PMC3376176

Abstract: The purpose of the present study was to examine the relative association of genetic and environmental factors with individual differences in each of the proximal, jointly necessary, and sufficient causes for suicidal behavior, according to the Interpersonal-Psychological Theory of Suicide (IPTS; Joiner, 2005). We examined data on derived scales measuring acquired capability, belongingness, and burdensomeness (the determinants of suicidal behavior, according to theory) from 348 adolescent male twins. Univariate biometrical models were used to estimate the magnitude of additive genetic (A), non-additive genetic (D), shared environmental (C), and nonshared environmental (E) effects associated with the variance in acquired capability, belongingness, and burdensomeness. The best fitting model for the acquired capability allowed for additive genetic and environmental effects, whereas the best fitting model for burdensomeness and belongingness allowed for shared and nonshared environmental effects. The present research extends prior work by specifying the environmental and genetic contributions to the components of the IPTS, and our findings suggest that belongingness and burdensomeness may be more appropriate targets for clinical intervention than acquired capability as these factors may be more malleable or amenable to change.

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.