Adoptive Siblings Research Articles

Genetic and Familial Environmental Influences on the Risk for Drug Abuse

Prior research suggests that drug abuse (DA) is strongly influenced by both genetic and familial environmental factors. No large-scale adoption study has previously attempted to verify and integrate these findings. To determine how genetic and environmental factors contribute to the risk for DA. Follow-up in 9 public databases (1961-2009) of adopted children and their biological and adoptive relatives. Sweden. The study included 18 115 adopted children born between 1950 and 1993; 78,079 biological parents and siblings; and 51,208 adoptive parents and siblings. Drug abuse recorded in medical, legal, or pharmacy registry records. Risk for DA was significantly elevated in the adopted offspring of biological parents with DA (odds ratio, 2.09; 95% CI, 1.66-2.62), in biological full and half siblings of adopted children with DA (odds ratio, 1.84; 95% CI, 1.28-2.64; and odds ratio, 1.41; 95% CI, 1.19-1.67, respectively), and in adoptive siblings of adopted children with DA (odds ratio, 1.95; 95% CI, 1.43-2.65). A genetic risk index (including biological parental or sibling history of DA, criminal activity, and psychiatric or alcohol problems) and an environmental risk index (including adoptive parental history of divorce, death, criminal activity, and alcohol problems, as well as an adoptive sibling history of DA and psychiatric or alcohol problems) both strongly predicted the risk for DA. Including both indices along with sex and age at adoption in a predictive model revealed a significant positive interaction between the genetic and environmental risk indices. Drug abuse is an etiologically complex syndrome strongly influenced by a diverse set of genetic risk factors reflecting a specific liability to DA, by a vulnerability to other externalizing disorders, and by a range of environmental factors reflecting marital instability, as well as psychopathology and criminal behavior in the adoptive home. Adverse environmental effects on DA are more pathogenic in individuals with high levels of genetic risk. These results should be interpreted in the context of limitations of the diagnosis of DA from registries.

Journal Digest

Journal Digest

Confirming the etiology of adolescent acting-out behaviors: an examination of observer-ratings in a sample of adoptive and biological siblings.

A recent meta-analysis revealed moderate shared environmental influences (C) on most forms of child and adolescent psychopathology (Burt, 2009), including antisocial behavior. Critically, however, the research analyzed in this meta-analysis relied largely on specific informant-reports (and particularly parent and child reports), each of which is subject to various sources of rater bias. Observer-ratings of children's behaviors avoid many of these biases, and are thus well suited to verify the presence of C. Given this, we sought to buttress the evidence supporting C in two key ways. First, we sought to confirm that C contributes to observer-ratings in a sample of adoptive siblings, as similarity between adoptive siblings constitutes a 'direct' estimate of C. Second, we sought to confirm that these shared environmental influences persist across informants (i.e., the effects are not specific to the rater or the context in question). The current study examined the etiology of observer-ratings of acting-out behaviors, as well as sources of etiological overlap across observer-ratings, adolescent self-report and maternal-report in sample of over 600 biological and adoptive sibling pairs from the Sibling Interaction and Behavior Study (SIBS). Results revealed moderate and significant shared environmental influences on observer-ratings (31%), as well as on the other informant-reports (20-23%). Moreover, a portion of these effects overlapped across measures (C correlations ranged from .32 to .34). Such findings argue against passive gene-environment correlations (rGE) and rater bias as primary explanations for earlier findings of C on antisocial behavior, and in this way, offer a critical extension of prior work indicating that the role of shared environmental influences on child and adolescent antisocial behavior was dismissed too soon.

Genetic Influences on Incidence and Case-Fatality of Infectious Disease

BackgroundFamily, twin and adoption studies suggest that genetic susceptibility contributes to familial aggregation of infectious diseases or to death from infections. We estimated genetic and shared environmental influences separately on the risk of acquiring an infection (incidence) and on dying from it (case fatality).MethodsGenetic influences were estimated by the association between rates of hospitalization for infections and between case-fatality rates of adoptees and their biological full- and half- siblings. Familial environmental influences were investigated in adoptees and their adoptive siblings. Among 14,425 non-familial adoptions, granted in Denmark during the period 1924–47, we selected 1,603 adoptees, who had been hospitalized for infections and/or died with infection between 1977 and 1993. Their siblings were considered predisposed to infection, and compared with non-predisposed siblings of randomly selected 1,348 adoptees alive in 1993 and not hospitalized for infections in the observation period. The risk ratios presented were based on a Cox regression model.ResultsAmong 9971 identified siblings, 2829 had been hospitalised for infections. The risk of infectious disease was increased among predisposed compared with non-predisposed in both biological (1.18; 95% confidence limits 1.03–1.36) and adoptive siblings (1.23; 0.98–1.53). The risk of a fatal outcome of the infections was strongly increased (9.36; 2.94–29.8) in biological full siblings, but such associations were not observed for the biological half siblings or for the adoptive siblings.ConclusionRisk of getting infections appears to be weakly influenced by both genetically determined susceptibility to infection and by family environment, whereas there appears to be a strong non-additive genetic influence on risk of fatal outcome.

Family Likeness: Sex, Marriage, and Incest from Jane Austen to Virginia Woolf (review)

Reviewed by: Family Likeness: Sex, Marriage, and Incest from Jane Austen to Virginia Woolf Tess O'Toole (bio) Family Likeness: Sex, Marriage, and Incest from Jane Austen to Virginia Woolf by Mary Jean Corbett; pp. 264 Ithaca: Cornell UP, 2008. $26.05. As familiar and well-mined a topic as the Victorian marriage plot is, Mary Jean Corbett's fascinating study allows us to view it afresh by attending to the "cultural meanings" (175) attached to incest in nineteenth-century Britain. Our critical tradition, Corbett suggests, has overemphasized both the cultural injunction to exogamy in the period and the generic plot of "romance between strangers" (vii). But in an era when the distinction between consanguinity and affinity (relationships created by marriage) was contested, affective bonds between siblings and cousins informed conjugal bonds in powerful and complex ways. In compelling readings of narratives depicting what she terms "marriage within the family" (34) in such forms as marriage with a cousin, a deceased wife's sister, or an adoptive sibling, Corbett encourages us to rethink not only Victorian novels but also our own normative models of family life. Corbett approaches incest as an "historically variable concept" (68) that in the Victorian context, connoted "a different set of perceived transgressions [End Page 244] than we associate with the term today" (7). She charts its changing valences and the practical forms it assumed throughout the nineteenth century, tracking in particular the way its definition gradually disentangled biological and affinal forms of relationship defining incest as well as the complicated and counterintuitive overlaps between concerns about incest and about the practice that would appear to be its exogamous opposite, miscegenation (a relationship she makes especially visible in a reading of Wuthering Heights). Central to Corbett's reconstruction of this history is the debate over the law that prohibited a widower from marrying his sister-in-law. Repeal of the prohibition with the passage of the Deceased Wife's Marriage Act in 1907 was a watershed: decriminalizing affinal incest, it "effectively enabled the institution of legal penalties for consanguineal incest" a year later and paved the way for our own cultural understanding of the term (4). But for the ban's Victorian proponents and opponents alike, Corbett argues, the affective charge of the wife's unmarried sister reveals an "ambiguity in the boundaries of the family" (59) that is central to what she defines as "nineteenth-century middle-class incests" (19). In that ambiguity, Corbett finds openness and possibility. In a surprising and persuasive reading of Mansfield Park, for instance, she invites us to imagine "the force and scope the now-anomalous alternative plot of marriage within the family had for Austen's original audience" (55) and argues that Austen's characters "have opportunities to maintain and extend kinship ties ... through the creation of second families not exclusively centered on the heterosexual couple and its offspring" (56). She locates a similar flexibility in Gaskell's Wives and Daughters, where the blended family formed by Dr. Gibson's remarriage and the figurative adoption of Molly Gibson by the Hamleys mediate the courtship plot in a way that suggests family relations are "not ... fixed or given ... [but rather] malleable, situational, and fungible ... [depending on] action more than essence" (148). Thus, while the literary trope of incest has generally been associated with contraction and enclosure, Corbett's approach identifies it with expansiveness and extension; this is perhaps the most revisionary aspect of her study. Like the work of Sharon Marcus, whose Between Women: Friendship, Desire, and Marriage in Victorian England Corbett references several times, Family Likeness productively reframes the critical conversation around domestic fiction. Particularly impressive is Corbett's deft integration of the personal narrative—the affective dimension of the negotiation between first-family and conjugal bonds, the potential of "marriage within the family" to foster a woman's agency—with the cultural narrative whereby the "middle-class incests" depicted in the marriage plots she addresses were poised against and increasingly distinguished from working-class pathologies of family life (13). She considers fictional texts alongside legal, political, and scientific treatises that work through related problems: Henry Maine's anthropological account of adoption, for instance, frames Corbett's account of...

Behavioral Adjustment of Adopted Chinese Girls in Single-Mother, Lesbian-Couple, and Heterosexual-Couple Households

This study compared the behavioral adjustment of girls from families headed by single mothers and lesbian couples with their peers from married heterosexual households. The sample included 93 Chinese girls adopted by the three types of families (31 girls in each type of family). The girls in the three types of families were matched on age at adoption, age at assessment, and number of adoptive siblings. The Child Behavior Checklist was used to measure their behavior adjustment (i.e., internalizing problems, externalizing problems, and overall behavioral problems). General linear modeling revealed that children from the three types of families were not statistically different in behavioral adjustment except in the preschool-aged group's internalizing problems and the school-aged group's externalizing problems, wherein children in single-mother households scored lower than their peers from lesbian-couple households. Psychological and social-political implications are discussed.

Environmental contributions to the stability of antisocial behavior over time: are they shared or non-shared?

It has recently been argued that shared environmental influences are moderate, identifiable, and persistent sources of individual differences in most forms of child and adolescent psychopathology, including antisocial behavior. Unfortunately, prior studies examining the stability of shared environmental influences over time were limited by possible passive gene-environment correlations, shared informants effects, and/or common experiences of trauma. The current study sought to address each of these limitations. We examined adolescent self-reported antisocial behavior in a 3.5 year longitudinal sample of 610 biological and adoptive sibling pairs from the Sibling Interaction and Behavior Study (SIBS). Results revealed that 74-81% of shared environmental influences present at time 1 were also present at time 2, whereas most non-shared environmental influences (88-89%) were specific to a particular assessment period. Such results provide an important constructive replication of prior research, strongly suggesting that shared environmental contributions to antisocial behavior are systematic in nature.

Are there shared environmental influences on adolescent behavior? Evidence from a study of adoptive siblings.

The failure to identify specific non-shared environmental influences on behavior coupled with the belief that shared environmental factors contribute minimally to individual differences in behavior has led to the concern that major environmental determinants of behavior may be idiosyncratic, and therefore undetectable. We used data on adoptive (N = 246) and biologically related (N = 130) same-sex sibling pairs (mean ages = 16.1 years older sibling; 13.8 years younger sibling) from the Sibling Interaction and Behavior Study (SIBS) to determine whether non-idiosyncratic environmental factors shared by siblings contributed to individual differences in a diverse set of behavioral outcomes. Evidence for shared environmental influence was sought for eight composite measures covering a wide array of adolescent functioning: Academic Achievement, Total IQ, Substance Use Disorders, Externalizing Disorders, Internalizing Disorders, Peer Groups, Disinhibited Personality, and Negative Emotionality. For six of eight composites, significant shared environmental effects, accounting for 14-22% of the variance, were observed for these same-sex sibling pairs. These findings support the use of adoptive sibling designs to directly estimate shared environmental effects and implicate the existence of systematic environmental influences on behavior that are potentially detectable.

Shared-environmental contributions to high cognitive ability.

Using a combined sample of adolescent twins, biological siblings, and adoptive siblings, we estimated and compared the differential shared-environmentality for high cognitive ability and the shared-environmental variance for the full range of ability during adolescence. Estimates obtained via multiple methods were in the neighborhood of 0.20, and suggest a modest effect of the shared environment on both high and full-range ability. We then examined the association of ability with three measures of the family environment in a subsample of adoptive siblings: parental occupational status, parental education, and disruptive life events. Only parental education showed significant (albeit modest) association with ability in both the biological and adoptive samples. We discuss these results in terms of the need for cognitive-development research to combine genetically sensitive designs and modern statistical methods with broad, thorough environmental measurement.

Eastern European adoption: policies, practice, and strategies for change

Between 1990 and 2004, more than 68,000 children born in Europe were adopted into American families. Almost two-thirds of these children came from Russia. And in contrast to children adopted from Korea, China, Central America, and South America, most of the Russian children were not infants, but between one and four years old. This volume addresses adoption policies and practices as they pertain to adopted children from Europe, children who have histories of pre-adoption adversity. Drawing on her decade-long experience as an adoptive parent of siblings born in Russia and her expertise as an applied sociologist, Josephine Ruggiero examines the central issues involved in international adoptions, focusing on older children as well as siblings, and suggesting needed changes in policy and practice. Regardless of whether children are adopted domestically or internationally, age is a significant factor in their ability to adjust to and function well in their new families. Only about three in ten Russian adoptees joined their new families as infants. Pre-adoption experiences are also significant factors in a child's ability to adjust and function well in a new family. Countries differ in risk factors that may figure into the likelihood of adoptees adapting to life in a new family. Fetal Alcohol Syndrome, serious medical conditions, emotional problems, behavioral problems, attachment issues, learning disabilities, and exposure to family violence must be considered as potential risk factors in adoptions. Pre-adoption adversity is less likely when children from birth families that are economically poor but have bonded with them. At a time when adoption has finally come out of the closet and the definition of the family is changing dramatically, Eastern European Adoption takes a much-needed look at current adoption policies and practices and how well they do or do not work. Ruggiero draws on the literature on older-child and sibling adoption, and data from a questionnaire survey she designed and conducted with 121 adoptive parents. Ruggiero's examples from real adoptive families give a human face to the issues, needs, and strategies she discusses.

‘One in, One Out’?: The Dilemma of having Multiple Children in Foster Placements

Practitioners in a specialist service for looked after children and their carers have indicated a tendency for children to be placed in households where there are multiple foster children. This has led to concern that previously settled children's placements were disrupting following the introduction of a new child into the household. A file audit was conducted to gather information regarding the incidence of disruption and the contributing factors, as reported in clients' files. While the study reported here by Germaine Ingley and Louise Earley did not show a high rate of movement into placements, it did indicate that when a new child was moved into the home of an already ‘established’ child, the ‘established’ child's placement often disrupted. In addition, qualitative information obtained from files and letters revealed that conflicts with another child in placement, either a sibling or unrelated child, was the most frequently cited factor associated with disruption. Attachment literature and ideas from the study of adoptive families and sibling relationships in birth families are drawn upon to explain these findings, and recommendations are made to lessen the potential difficulties associated with the multiple placements of children in foster homes.

Genetic and Environmental Effects on Mortality Before Age 70 Years

There is a familial influence on risk of many diseases and on mortality in general, which, according to studies of twins, is due to a combination of genetic and environmental effects. Adoption studies, which rest on different assumptions, may also be used to estimate separately the genetic and environmental effects on rate of dying. The genetic influence on the rate of dying before age 70 years was investigated by estimation of the associations in total and cause-specific mortality of Danish adoptees and their biologic full and half siblings. Familial environmental influences shared at the same time in life were investigated in adoptees and their adoptive siblings. The study basis is the 14,425 nonfamilial adoptions formally granted in Denmark during the period 1924 through 1947, recorded in the Danish Adoption Register. From this register we selected the 1552 "case" adoptees (who died before 01 April 1993) and 1710 "noncase" adoptees alive at that date. The siblings of the case and noncase adoptees were traced in the archives and followed forward, and the rates of dying before age 70 years were compared. Compared with mortality of the biologic siblings of noncase adoptees, the mortality of biologic siblings of dead adoptees was approximately 2-fold higher for death with infections and vascular causes, and around 45% increased for natural causes and for all causes. The results suggest that there is a genetic effect on the rate of death with infections, vascular causes, natural causes and all causes, whereas there is no indication of an influence of shared sibling environment.

A sibling adoption study of adult attachment: The influence of shared environment on attachment states of mind

This study extends existing research investigating sibling concordance on attachment by examining concordance for adult attachment in a sample of 126 genetically unrelated sibling pairs. The Adult Attachment Interview (George, Kaplan, & Main, 1985; Main, Goldwyn, & Hesse, 2003) was used to assess states of mind with regard to attachment. The average age of the participants was 39 years old. The distribution of attachment classifications was independent of adoptive status. Attachment concordance rates were unassociated with gender concordance and sibling age difference. Concordance for autonomous/non-autonomous classifications was significant at 61% as was concordance for primary classifications at 53%. The concordance rate for not-unresolved/unresolved was non-significant at 67%. Our findings demonstrate similarity of working models of attachment between siblings independent of genetic relatedness between siblings and generations (i.e., parent and child). These findings extend previous research by further implicating shared environment as a major influence on sibling similarities on organized patterns of attachment in adulthood. The non-significant concordance for the unresolved classification suggests that unresolved loss or trauma may be less influenced by shared environment and more likely to be influenced by post-childhood experiences or genetic factors.

The Environments of Adopted and Non-adopted Youth: Evidence on Range Restriction From the Sibling Interaction and Behavior Study (SIBS)

Previous reviews of the literature have suggested that shared environmental effects may be underestimated in adoption studies because adopted individuals are exposed to a restricted range of family environments. A sample of 409 adoptive and 208 non-adoptive families from the Sibling Interaction and Behavior Study (SIBS) was used to identify the environmental dimensions on which adoptive families show greatest restriction and to determine the effect of this restriction on estimates of the adoptive sibling correlation. Relative to non-adoptive families, adoptive families experienced a 41% reduction of variance in parent disinhibitory psychopathology and an 18% reduction of variance in socioeconomic status (SES). There was limited evidence for range restriction in exposure to bad peer models, parent depression, or family climate. However, restriction in range in parent disinhibitory psychopathology and family SES had no effect on adoptive-sibling correlations for delinquency, drug use, and IQ. These data support the use of adoption studies to obtain direct estimates of the importance of shared environmental effects on psychological development.

The role of conduct disorder in explaining the comorbidity between alcohol and illicit drug dependence in adolescence

Background Conduct disorder (CD), alcohol dependence (AD), and illicit drug dependence (IDD) frequently co-occur. This paper describes the result of an investigation of the extent to which comorbid alcohol and illicit drug dependence in adolescents are explained by etiological factors in common with conduct disorder. Methods Participants were 645 MZ twin pairs, 702 DZ twin pairs, 429 biological sibling pairs, and 96 adoptive sibling pairs, aged 12–18 years, from a community based sample. Conduct disorder was measured using the Diagnostic Interview Schedule for Children-IV. Alcohol and illicit drug dependence were assessed using the Composite International Diagnostic Interview-Substance Abuse Module (CIDI-SAM). For each outcome, subjects were categorized into those with no symptoms, those with one or more symptoms but no diagnosis, and those with a diagnosis. Results The heritability estimates for CD, AD, and IDD were 58, 66, and 36%, respectively. The genetic correlation between AD and IDD was partially explained by the genetic risk they both share with conduct disorder. Conclusions We conclude that conduct disorder in adolescents explains, in part, the co-occurrence of alcohol and illicit drug dependence. Specifically, the genetic contribution to their covariation is explained partially by the genetic contribution in common with conduct disorder.

Genetic and Environmental Influences on Age at Sexual Initiation in the Colorado Adoption Project

Whereas the majority of research on adolescent sexual initiation has focused solely on environmental factors, the present study used behavioral genetic analyses to investigate the relative contributions of genetic and environmental influences. Structural equation models were fitted to data from adoptive and non-adoptive sibling pairs (231 biologically related pairs and 169 unrelated pairs) from the Colorado Adoption Project. Information from censored individuals who had not yet experienced sexual initiation was maximized by adapting the twin survival analysis method of Pickles et al. (Behav Genet 24(5):457-468, 1994) to accommodate adoptive and non-adoptive siblings. Point estimates of variance components from an ACE model, including additive genetic (A), shared environmental (C), and non-shared environmental (E) influences were 28%, 24%, and 48%, respectively. Despite the lower point estimate for shared environmental effects than additive genetic effects, a CE model provided the best fit to the data. However, because adoptive siblings provide a direct estimate of shared environmental influences there is greater power to detect shared environmental effects in adoption designs. Evidence for genetic influences from our data were somewhat lower than those obtained in previous twin studies, possibly reflecting a return to more socially conservative sexual attitudes, changing sexual behaviors, or ambiguities in the wording of questions commonly used in research on adolescent sexuality.

Genetic and Environmental Vulnerabilities Underlying Adolescent Substance Use and Problem Use: General or Specific?

Are genetic and environmental risks for adolescent substance use specific to individual substances or general across substance classes? We examined this question in 645 monozygotic twin pairs, 702 dizygotic twin pairs, 429 biological sibling pairs, and 96 adoptive (biologically unrelated) sibling pairs ascertained from community-based samples, and ranging in age from 12 to 18 years. Substance use patterns and symptoms were assessed using structured psychiatric interviews. Biometrical model fitting was carried out using age- and sex-specific thresholds for (a) repeated use and (b) problem use, defined as one or more DSM-IV symptoms of abuse or dependence. We hypothesized that problem use would be more heritable than use in adolescence, and that both genetic and environmental risks underlying tobacco, alcohol, and marijuana use and problem use would be significantly correlated. Results of univariate analyses suggested significant heritable factors for use and problem use for all substances with the exception of alcohol use. Shared environmental factors were important in all cases and special twin environmental factors were significant for tobacco use, tobacco problem use, and alcohol use. Multivariate analyses yielded significant genetic correlations between each of the substances (for both levels studied), and significant shared environmental correlations among use variables only. Our results suggest that tobacco, alcohol, and marijuana problem use are mediated by common genetic influences, but shared environmental influences may be more substance-specific for problem use.

Reading Skills in Early Readers

The present study combined parallel data from the Northeast-Northwest Collaborative Adoption Projects (N2CAP) and the Western Reserve Reading Project (WRRP) to examine sibling similarity and quantitative genetic model estimates for measures of reading skills in 272 school-age sibling pairs from three family types (monozygotic twins, dizygotic twins, and unrelated adoptive siblings). The study included measures of letter and word identification, phonological awareness, phonological decoding, rapid automatized naming, and general cognitive ability. Estimates of additive genetic effects and shared environmental effects were moderate and significant. Furthermore, shared environmental effects estimated in twins were generally similar in magnitude to adoptive sibling correlations, suggesting highly replicable estimates across different study designs.

Thanks for the Sibling Adoption Article

Thanks for the Sibling Adoption Article

(Letters) Thanks for Sibling Adoption Article

In my work as an adoption supervisor at Children and Family Services in Cleveland, Ohio, I have been using the article “Siblings and Out-Of-Home Placements: Best Practices” [October-December issue, 2003]. Several times in the past 6 months I have used the article in situations where I believe that the people involved do not have a clear understanding of the importance of the sibling bond. I have also given it to all my workers and we have discussed it at our unit meeting. Many of my colleagues have found the article very informative and useful. In one instance, one of my workers was convinced that there was no problem in separating siblings currently on her caseload, but once she read through the article she had a different opinion. The article has been especially helpful in difficult situations.