Introduction

SIBLINGS OF INDIVIDUALS WITH AUTISM

SPECTRUM DISORDERS ACROSS THE LIFE COURSE

Gael I. Orsmond1* and Marsha Mailick Seltzer2 1Department of Occupational Therapy and Rehabilitation Counseling, Boston University, Boston, Massachusetts

2Waisman Center, University of Wisconsin-Madison, Madison, Wisconsin

In this article, we review the literature on siblings of individuals with autism spectrum disorders (ASD) from a lifespan developmental per- spective, from infancy through adulthood, focusing on the sibling rela- tionship and sibling well-being. We situate this review within the larger body of research on siblings of individuals with developmental disabilities (DD) across the lifespan. We then consider the genetic aspects of ASDs and their implications for siblings. We conclude that there is an evidence of atypical social and communication development in some siblings of children with an ASD during infancy. During childhood and adolescence, siblings describe both positive and negative aspects of their sibling rela- tionship and there is some evidence that siblings of children with an ASD may be at heightened risk for social and behavioral adjustment problems. The limited research on adulthood suggests that lack of closeness in the sibling relationship and social and emotional difficulties may continue. We encourage more attention focused on developmental issues, specifi- cally with respect to samples in narrower age groups and in longitudinal research. Finally, we note the variability in sibling outcomes, and suggest further examination of potential moderating and mediating factors, including genetic predispositions. ' 2007 Wiley-Liss, Inc.

MRDD Research Reviews 2007;13:313–320.

Key Words: siblings; lifespan; sibling relationship; well-being

In this article, we provide a developmental perspective onthe sibling relationship and well-being of siblings of indi- viduals with autism spectrum disorders (ASD). We use the

term ASD to include children with autism, Asperger syn- drome, and pervasive developmental disorders (PDD). All of these disorders share impairments in communication, social reciprocity, and the presence of restricted and repetitive behav- iors [APA, 2000]. We organize this review from a develop- mental perspective, discussing the literature on two topics, sib- ling relationships and sibling well-being, within each life stage, from infancy through adulthood. The term ‘‘sibling relation- ship’’ includes the physical actions and interactions between siblings, as well as the more subjective, cognitive, and affective components of the relationship [Cicirelli, 1995]. Research, therefore, has focused on the dimensions of companionship, affect, and caregiving in the sibling relationships. The term ‘‘sibling well-being’’ includes outcomes that represent well- being according to the age of the sibling, such as social engagement and communication in infancy, behavioral adjust- ment during childhood, and mental health in adolescence and adulthood.

Among all human relationships, sibling relationships typ- ically last the longest. The sibling relationship is also unique in that it is ascribed rather than achieved, and typically one of relative egalitarianism [Cicirelli, 1995]. Nurturance and con- flict in the sibling relationship provide siblings with experi- ences that foster the development of emotional understanding, self-regulation, and a sense of belonging and comfort [Brody, 2004]. Siblings begin as play partners and sources of support through intimate daily contact during childhood. During ado- lescence and young adulthood, siblings experience decreased contact and intimacy as they establish their independent lives. Intimacy in the sibling relationship during adulthood is main- tained through telephone and other forms of communication and through periodic visits. Thus, the sibling relationship in adulthood is more susceptible to change due to factors in the individual siblings’ lives [Cicirelli, 1995]. Finally, during mid- dle and later adulthood, sibling relationships often become more salient, especially when other family and social supports are less available [White, 2001].

The literature on siblings in the general population indi- cates that sibling relationships show considerable continuity throughout childhood and adolescence [Dunn et al., 1994], although more recent research has focused on the personal, interpersonal, and ecological variables that influence sibling relationships [Kramer and Kowal, 2005]. Overall, girls tend to report more affection and intimacy in their sibling relation- ships than boys [Akiyama et al., 1996; Kim et al., 2006], although the sex constellation may also make a difference. In a recent study, sibling intimacy was relatively stable in same-sex dyads from childhood through adolescence, but in mixed-sex dyads intimacy declined from middle childhood through early adolescence and then increased in middle adolescence [Kim et al., 2006]. With respect to parental influences, considerable

Grant sponsor: National Institute on Aging; Grant number: R01 AG08768; Grant sponsor: National Institute on Child Health and Human Development; Grant num- bers: P30 HD03352, R03 HD039185; Grant sponsor: Graduate School of the Uni- versity of Wisconsin-Madison. *Correspondence to: Gael I. Orsmond, Department of Occupational Therapy and Rehabilitation Counseling, Boston University, 635 Commonwealth Avenue, Boston, MA 02215. E-mail: [email protected] Received 20 August 2007; Accepted 22 August 2007 Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/mrdd.20171

MENTAL RETARDATION AND DEVELOPMENTAL DISABILITIES RESEARCH REVIEWS 13: 313 – 320 (2007)

' 2007Wiley -Liss, Inc.

research supports a positive association between positivity in the parent–child relationship and positive affect and pro- social behavior in the sibling relation- ship [Brody, 1998], although the relative importance of the mother–child versus the father–child relationship remains debated [Kim et al., 2006]. Further- more, children and adolescents who per- ceive that they receive less warm and more negative treatment from their parents than their siblings have greater emotional and behavioral difficulties, especially if they perceive that treatment to be unjust [Brody, 2004].

With these life course patterns and influences on the sibling relation- ship in mind, one additional factor that can influence the life course trajectory of the sibling relationship is the pres- ence of disability in a sibling. Consider- able research has examined how the sib- ling relationship is affected, and whether the well-being of the non-dis- abled sibling is impacted, when one sib- ling has a developmental disability (DD) other than an ASD [see Rossiter and Sharpe, 2001, for a review], but compa- ratively little research has focused on the sibling relationship when one sib- ling has an ASD. Therefore, we begin our review by summarizing the research on sibling relationships in DDs other than ASDs. This research is helpful in understanding how the presence of cog- nitive impairment affects sibling well- being and sibling relationships. Most individuals with ASDs have cognitive limitations, but they also have social and behavioral characteristics that might challenge the sibling relationship, such as impairment in social reciprocity and the presence of rigid behaviors [APA, 2000]. Thus, in understanding how ASDs affect the sibling relationship, it is helpful to contextualize our review within the larger body of research on siblings of individuals with DD other than ASDs.

SIBLINGS OF INDIVIDUALS WITH DEVELOPMENTAL DISABILITIES

In reviewing the research on sib- ling relationships when one sibling has a DD, Stoneman [2001, 2005] concluded that there are high levels of interaction when one sibling has a DD, especially during childhood, although some of this interaction is likely due to the expanded childcare roles that non-disabled sib- lings, especially sisters, often play. A meta-analytic review of the effects on the sibling relationship and sibling well- being came to a more negative conclu-

sion [Rossiter and Sharpe, 2001]. On the basis of 25 studies on siblings of individuals with DD, Rossiter and Sharpe concluded that there was a stat- istically significant but small negative effect on the psychological functioning of these siblings (depression, anxiety, and behavioral adjustment in terms of internalizing and externalizing behav- iors). The effect varied at different stages of the life. The effects for siblings during childhood and adolescence were negative, although only the effect size for childhood was significant. The effect size for siblings during adulthood was positive but not significantly different from zero. Rossiter and Sharpe com- ment on these age-related findings, pointing out that only two studies were included in the analysis regarding adult siblings, and pondering whether the findings reflect effects due to self-report (which tend to be more positive than parental reports across ages) versus pa- rental report (which is more common in studies on children and adolescents). Rossiter and Sharpe [2001] also specu- late that the effect on siblings during adulthood may be less negative because of the decreased influence of the birth family on adults and also possibly because of the development of more mature and effective coping strategies. These observations of age-related differ- ences in the effects of the sibling rela- tionship underscore the importance of a life course perspective when assessing the impact of a sibling with a disability.

Our own research substantiates that sibling relationships are relatively positive during adulthood, and also pro- vides considerable information regard- ing the factors that affect sibling rela- tionships during this life stage [see Selt- zer et al., 2005, for a recent review]. We have found that non-disabled sib- lings are often considered a member of the social support network of adult brothers and sisters with a DD [Krauss et al., 1992], and that the sibling who is most involved has a considerable amount of contact and relatively posi- tive relationships with the brother or sister [Krauss et al., 1996], especially in comparison with siblings who have a brother or sister with mental illness (MI) [Seltzer et al., 1997]. Siblings of adults with DD generally provide higher levels of emotional rather than instrumental support [Seltzer et al., 1991], and provide more emotional support than siblings of adults with MI [Greenberg et al., 1999].

We have also found that sibling gender has important effects on sibling

caregiving and involvement. The most involved sibling is likely to be a sister [Seltzer et al., 1991], and she is likely to have an equally close relationship if she has a sister or brother with DD [Ors- mond and Seltzer, 2000]. Brothers’ sib- ling relationships are conditioned by the gender of their sibling; brothers with a brother with DD have closer relation- ships than brothers with a sister with DD. Furthermore, there is considerable variability regarding expectations of future caregiving roles [Krauss et al., 1996]. Although almost 20% of siblings expected to have their sibling with DD live with them in the future [Krauss et al., 1996], when followed up at a later point in time only 10% of siblings actually coresided [Freedman et al., 1997]. Finally, we found that when the sibling with DD moves out of the pa- rental home to a community residential living arrangement, non-disabled sib- lings tend to be less worried about their brother or sister’s future and have increased contact with their sibling, when compared with siblings when the brother or sister continues to live at home [Seltzer et al., 2001]. Thus, our research indicates that during adult- hood, sibling relationships are relatively positive but are more likely to involve emotional support than direct caregiv- ing. Furthermore, gender of both sib- lings and living arrangement of the brother or sister with DD (in the paren- tal home, elsewhere) are important fac- tors contributing to sibling closeness.

We now turn to the literature on siblings of individuals with ASDs, focus- ing on the sibling relationship and sib- ling well-being. However, first we begin with a brief review of the genetic basis of ASDs.

THE GENETIC BASIS OF ASDS We need to consider both genetic

and environmental effects when exam- ining the impact of ASDs on siblings. There is a general consensus that there is a genetic basis to autism [see Rutter, 2000; Wassink et al., 2004; for reviews]. Siblings of individuals with an ASD are at greater risk for ASDs themselves as well as a range of related impairments. This is termed the ‘‘broader autism phe- notype’’ (BAP) [Baurminger and Yir- miya, 2001]. Concordance rates for monozygotic twins range from 60 to 96% [Bailey et al., 1995; Ritvo, 1985] and from 0 to 24% for dizygotic twins [Bailey et al., 1995; Ritvo, 1985]. Re- currence rates (meaning the occurrence of an ASD in another immediate family member) for ASDs in siblings have con-

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sistently been reported in the 3–5% range [Micali et al., 2004]. Therefore, any consideration of the impact on a non-diagnosed sibling who has a brother or sister with an ASD must take the BAP into account when interpret- ing the data, and acknowledge its potential to increase the vulnerability of siblings who do not have an ASD. Thus, it is ultimately not possible to fully differentiate BAP (i.e., genetic) factors from the reactive effects of growing up with a sibling with an ASD (i.e., environmental factors).

PRIOR REVIEWS OF THE WELL-BEING OF BROTHERS AND SISTERS OF INDIVIDUALS WITH AN ASD

There are no prior reviews of research on the sibling relationship when one sibling has an ASD. How- ever, there have been prior reviews on the well-being of such siblings. The most recent review on the cognitive and psychiatric outcomes of siblings of individuals with an ASD is a meta-anal- ysis and methodological critique of 18 studies by Yirmiya et al. [2001], which concluded that there is insufficient data to support the notion that siblings of children with an ASD are at increased risk for negative cognitive and psychiat- ric outcomes, with the exception of the increased genetic risk of ASDs (including the BAP). They note several limitations in the literature that preclude firm conclusions: the relatively small number of studies that are comparable to one another; the small samples stud- ied, which makes it difficult to observe recurrence if rates are low; and the lack of comparison groups that also have genetic liabilities such as siblings of individuals with learning disabilities or psychiatric disorders.

Other reviews include a summary of the research by Bauminger and Yirmiya [2001] and a comprehensive review by Lainhart [1999] on the pres- ence of psychiatric problems in siblings (and other relatives) of individuals with an ASD. Lainhart’s review concluded that first degree-relatives of individuals with an autism (including siblings) are at increased risk of major depression, but the findings for other psychiatric disorders are mixed. The current review differs from these prior ones in that we examine both the sibling relationship and sibling well-being, and attempt to understand sibling outcomes in siblings of individuals with an ASD according to life stage, from infancy through adulthood.

SIBLINGS OF INDIVIDUALS WITH AN ASD IN INFANCY

A relatively recent development in the research literature on siblings of individuals with an ASD has been a focus on infant siblings. Although a pri- mary purpose of this research is to identify atypical patterns of develop- ment that may be early markers for ASDs, these studies also provide infor- mation regarding the development of such siblings during the early years of life. In line with the skills of infants, these studies have focused on the devel- opment of social engagement and com- munication [Goldberg et al., 2005; Zwaigenbaum et al., 2005; Mitchell et al., 2006; Yirmiya et al., 2006].

At a very young age, 4-month- old siblings of children with autism did not differ from siblings of typically developing (TD) children on most measures of early social engagement, such as infant gaze, positive or negative affect when the mother stopped inter- acting with the infant, and their response to their mother when she started inter- acting with them again. However, their interactions with their mothers were less synchronous when they began the interaction, and they showed more neu- tral affect and were less likely to cry when their mother stopped interacting with them [Yirmiya et al., 2006]. Inter- estingly, more infant siblings of children with autism responded to their name being called than siblings of TD chil- dren. In another study, at 12 months of age, atypical language skills, imitation, and responsiveness to social and nonso- cial stimuli were observed, which were later found to be related to the develop- ment of an ASD in some siblings [Zwaigenbaum et al., 2005].

At age 14 months, Yirmiya et al. [2006] found no differences between siblings of children with an ASD when compared with siblings of TD children on cognitive or motor development, but siblings of children with an ASD showed delayed requesting behaviors. Goldberg et al. [2005] reported similar findings regarding language and early social communication behaviors. At 14–19 months, infant siblings of chil- dren with an ASD showed significantly less eye contact, fewer gestures, less turn-taking, less pointing and showing behaviors, and fewer requesting behav- iors than siblings of TD children. Gold- berg and colleagues also found that sib- lings not later diagnosed with an ASD performed more similarly to siblings later diagnosed with an ASD on these social and communication behaviors

than they did in comparison to siblings of TD children.

In contrast, Mitchell et al. [2006] found that at 12 months, siblings not later diagnosed with an ASD were simi- lar to siblings of TD children on lan- guage and communication skills, but that by 18 months siblings of children with an ASD produced fewer play- related gestures than the TD group. Differences across these studies on infant siblings of children with an ASD likely arise because of the small samples, which may not be representative of the population, and differences in the types of measures used.

These infant sibling studies sug- gest some evidence of difficulties in social and communication behavior at a young age, even in siblings who are not later diagnosed with an ASD. The authors of these infant sibling studies argue that these developmental differen- ces are due to genetic liability, although Yirmiya et al. [2006] acknowledge that the findings may be due in part to envi- ronmental effects. Social relationships and mother–child interactions in the family could be affected by the presence of the sibling with an ASD or the pres- ence of BAP characteristics in mothers, independent of the BAP characteristics in siblings.

SIBLINGS OF INDIVIDUALS WITH AN ASD IN CHILDHOOD AND ADOLESCENCE

Sibling Relationships During childhood, siblings of

children with an ASD spend a consider- able amount of time with their brother or sister. In an observational study of siblings ages 2–12, siblings spent on av- erage 40 minutes out of every hour to- gether when observed at home, and engaged in a variety of activities to- gether, including pretend and rough and tumble play [Knott et al., 1995]. However, the siblings of children with autism spent less time together than sib- lings of children with Down syndrome (DS), and their brother or sister with autism responded less positively to ini- tiations by the sibling. Another study using self-reports from siblings found that siblings of brothers and sisters with autism ages 7–12 expressed primarily positive feelings about their sibling rela- tionship [Rivers and Stoneman, 2003].

The majority of studies on sib- lings of children with autism have grouped together siblings spanning the childhood and adolescent years, obscur- ing differences between these stages of

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life. These studies agree that siblings describe the relationship with the brother or sister with autism in positive terms, although some negative aspects are noted, such as embarrassment or and disruptive behavior by the brother or sister with an ASD. Several studies show the similarity between sibling relationships when a sibling has an ASD when compared with a DD other than an ASD in terms of qualitative descrip- tions of the sibling relationship by sib- lings [Fisman et al., 1996, 2000; Pilow- sky et al., 2004].

Roeyers and Mycke [1995] found no differences between siblings ages 8 and 14 of children with autism when compared with siblings of children with DD, but siblings of children with autism reported more acceptance and less verbal aggression compared with siblings of TD children. In a study by Kaminsky and Dewey [2001], siblings ages 8–18 of children with autism reported greater admiration of and less competition and conflict with their brother or sister than siblings of TD children, and were simi- lar to siblings of children with DS in these aspects of the sibling relationship. However, they reported lower levels of closeness and intimacy than siblings of children with DS.

In terms of activities that siblings do together, in a qualitative study, almost half of the siblings ages 7–20 mentioned the good nature of their brother or sister with autism and that they played and had fun together, although feelings of embarrassment were also mentioned as well as concerns for the future of their brother or sister [Mascha and Boucher, 2006]. The most frequent activities they engaged in were playing together, watching television, and spending time outside.

Negative aspects of the relation- ship have also been identified by sib- lings. Some siblings reported greater feelings of embarrassment than siblings of children with DD or no disability [Roeyers and Mycke, 1995]. In a study by Ross and Cuskelly [2006], 84% of siblings (ages 8–15) reported aggression by the brother or sister with autism in their sibling interactions, which pro- voked feelings of anger. B€agenholm and Gillberg [1991] found that siblings ages 5–20 of children with autism played and interacted less with their brother or sister than siblings who had a brother or sister with DD. Furthermore, siblings of children with autism reported less favor- able attitudes toward their brother or sister and saw their brother or sister’s role in the family more negatively than

siblings who had a brother or sister with DD. More than half of the siblings of children with autism were unable to explain their brother or sister’s disability, and one-third said they could only talk with someone outside their family about their brother or sister’s condition. They also reported problems with de- structive behavior in their brother or sister, and were concerned about their brother or sister’s future.

In summary, siblings during child- hood and adolescence describe positive aspects of their sibling relationship, including siblings as activity partners, greater admiration, and less competition and conflict. There are also significant indications, however, that sibling rela- tionships are less close when the brother or sister has an ASD than when they have DS or a DD other than an ASD. Siblings also are concerned about embarrassment, destructive behavior, social isolation, and their brother or sis- ter’s future.

Sibling Well-Being Studies examining sibling well-

being have either included siblings spanning the childhood and adolescent years, or only focused on adolescent siblings. Notably, no studies of sibling well-being specifically during childhood have been conducted.

From a genetics perspective, sev- eral researchers have studied social and emotional skills associated with the BAP. Dorris et al. [2004] found that siblings ages 7–17 of children with Asperger syndrome showed impairment in facial emotion recognition compared with siblings of TD children. Constan- tino et al. [2006] found evidence for subtle social impairments in male sib- lings ages 4–18 of children with autism. Using his Social Responsiveness Scale, siblings from multiple-incidence families were rated as having the highest degree of social impairment, followed by sib- lings with only one brother or sister with autism. Siblings of children with a variety of other psychological or behav- ioral disabilities had the lowest scores.

Further evidence of social difficul- ties comes from a study by B€agenholm and Gillberg [1991] wherein 35% of the siblings age 5–20 reported feeling lonely and that they had no friends. In con- trast, sibling of children with mental re- tardation in this study did not report the same degree of loneliness and sib- lings of children without disabilities reported no feelings of being lonely. Other researchers have found that sib- lings whose brother or sister had ASD

are equally or more socially competent than siblings of children with DS or no disability [Gold, 1993; Rodrigue et al., 1993; Kaminsky and Dewey, 2002; Verte et al., 2003]

The research examining psycho- logical well-being in this age range has focused on the presence of clinical psy- chiatric diagnosis as well as behavioral adjustment. Pilowsky et al. [2004] found no differences in rates of clinical diag- noses (including ADHD, ODD, and anxiety) between siblings ages 6–15 of children with autism, MR of unknown genetic etiology, and developmental lan- guage disorder. Gold [1993] studied sib- lings of boys with autism and found that they scored significantly higher on a screening measure of clinical depression than siblings of TD children.

A relatively large number of stud- ies have examined sibling behavioral adjustment during childhood through adolescence using parental report, fre- quently examining internalizing and externalizing types of behavior problems with the Achenbach Child Behavior Checklist [CBCL; Achenbach and Resclora, 2001]. Studies of children and adolescents tend to report higher levels of adjustment problems in siblings of children with an ASD than in siblings of children with no disability, with mixed findings as to how siblings of children with an ASD compare with siblings of children with other DDs such as DS.

Smith and Perry [2005] reported that 36% of siblings ages 6–16 of a brother or sister with an ASD had bor- derline to clinically significant internal- izing behavior problems and 20% had externalizing problems. Similarly, Verte et al. [2003] reported that siblings ages 6–16 of high functioning children with autism had significantly more internaliz- ing and externalizing behavior problems than siblings of TD children. Fisman et al. [1996] reported that siblings ages 8–16 of children with PDD had more internalizing behavior problems accord- ing to both parent and teacher report on the CBCL than siblings of children with DS or no disability. Externalizing behavior problems were elevated only according to parent report. Three years later, siblings of children with PDD no longer scored higher in internalizing behaviors according to parental report, but continued to exhibit higher levels of externalizing behaviors [Fisman et al., 2000].

Similarly, Rodrigue et al. [1993] found that siblings with a mean age of 9 years had significantly more internal- izing and externalizing behavior prob-

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lems than siblings of TD children, but not more than siblings of children with DS. Hastings [2003a,b] reported on the adjustment of siblings ranging in age from 4 to 16 years using the Strengths and Difficulties Questionnaire (SDQ). Compared to normative data, the sib- lings of children with autism had more peer problems, more overall adjustment problems, and lower levels of prosocial behavior. B€agenholm and Gillberg [1991] used the Rutter scales with sib- lings ages 5–20 and found that siblings of children with autism scored higher on the inattention/hyperactivity and conduct problems scales (externalizing types of behavior problems) than did siblings of TD children, but similar to siblings of children with DD (including DS). Almost all of these authors empha- size that although scores on the mea- sures of behavior adjustment may be elevated in siblings of children with an ASD, they are generally within the non-clinical range.

In several other studies, siblings of children with an ASD were not found to be at greater risk of adjustment prob- lems. Ferrari [1984] found no differ- ences in behavior problems on the CBCL between siblings ages 6–13 of brothers with PDD, diabetes, and no health or developmental problems. Both Gold [1993] and Kaminsky and Dewey [2002] found no differences in adjust- ment problems (as measured by the CBCL) between siblings ages 7–18 of children with autism and siblings of TD children (in both studies) and DS [Kaminsky and Dewey, 2002]. Two additional studies did not use compari- son groups, but examined adjustment problems in siblings in comparison to normative data. Mates [1990] found that home, school, and academic adjustment in siblings ages 5–17 of children with autism were not significantly different from normative samples. Ross and Cuskelly [2006] reported than mean scores of internalizing and externalizing behavior problems as measured by the CBCL by parent report were within the non-clinical range for a sample of sib- lings ages 8–15. Forty percent of the siblings were experiencing adjustment problems. With a larger sample of fami- lies participating in ABA therapy, Hast- ings [2003b] reported that siblings were reported as having fewer problems on the SDQ compared with the normative data.

Positive outcomes have been con- sistently noted in the domains of sibling self-concept and self-competence. Sev- eral authors have found that siblings of

children with an ASD report positive self-concept similar to norms [Mates, 1990] or comparison groups of siblings of TD children or children with DD or DS [Ferrari, 1984; B€agenholm and Gill- berg, 1991; Rodrige et al., 1993]. Simi- larly, Verte et al. [2003] found that self- concept did not differ for younger sib- lings ages 6–11, but that adolescent female siblings age 12–16 of children with high-functioning autism (HFA) had a more positive self-concept than adolescent females of TD siblings.

Some of these studies spanning the childhood and adolescent years have examined age-related differences in sib- ling well-being. These studies are mixed in their findings. Gold [1993] found that siblings ages 7–12 reported signifi- cantly fewer depressive symptoms than siblings ages 13–17. Similarly, Rodrigue et al. [1993] reported that siblings younger in age (mean age was 9.11 years) had fewer internalizing and exter- nalizing behavior problems than siblings older in age. In contrast, Hastings [2003b] found that older siblings (late childhood and adolescence) had higher prosocial behavior scores than younger children, and Verte et al. [2003] found that siblings ages 6–11 who had a brother or sister with HFA had more internalizing and externalizing behavior problems than siblings ages 12–16.

In our own research, we have focused on the psychological well-being of siblings during adolescence [ages 12–18; Orsmond and Seltzer, 2006]. With a sample of 57 siblings, just over one-third (36%) of siblings reported depressive symptoms at or above the clinical cut-off score of 16 on the Cen- ter for Epidemiological Studies Depres- sion Scale [Radloff, 1977] and 8.5% of siblings reported clinically relevant anxi- ety symptoms on the Reynolds Child Manifest Anxiety Scale [Reynolds and Richmond, 1978]. Notably, these levels of depressive and anxiety symptoms are comparable to levels found in adoles- cent community samples [Radloff, 1991; Dierker et al., 2001].

To summarize, the literature yields mixed results regarding whether there is a negative impact on siblings when they have a brother or sister with an ASD, perhaps both due to a genetic (i.e., the BAP) and an environmental influence. There are also some indica- tions that siblings are at greater risk of adjustment problems during childhood compared with siblings of TD children, with the risk possibly increasing during adolescence, although study findings are not consistent. The variability in these

findings is possibly due to small sample sizes, differences in age ranges of sib- lings who participated, and different measures used to examine well-being and adjustment. The research, however, has been consistent in noting that self- concept and self-competence do not appear to be negatively affected in sib- lings who have a brother or sister with an ASD and some studies observe com- parable levels of depression and anxiety as age peers without a sibling with a disability.

SIBLINGS OF INDIVIDUALS WITH AN ASD IN ADULTHOOD

Sibling Relationships There are few studies examining

the sibling relationship during adult- hood when one sibling has an ASD. Holmes and Carr [1991] included sib- lings ages 16 years and older who had an adult brother or sister with autism or DS. The two groups did not differ in their involvement in direct caregiving (and therefore the results were presented together for both groups). Over one- third of siblings helped their brother or sister during mealtimes. Both siblings who lived at home and those who lived away from the parental home often watched their brother or sister when their parents went out. Importantly, the mothers recognized siblings as a source of help in caring for the family member with autism or DS.

In our recent research, we have examined how sibling relationships are affected by an ASD during adulthood [Orsmond and Seltzer, 2007]. Com- pared with siblings of adults with DS, siblings of adults with an ASD had less contact with their brother or sister, reported lower levels of positive affect in the relationship, felt more pessimistic about their brother or sister’s future, and were more likely to report that their relationships with their parents had been affected. Different factors were associated with the sibling rela- tionship for each group. For siblings of adults with an ASD, a closer sibling relationship was observed when the sib- ling had lower education levels, lived closer to the brother or sister with an ASD, used more problem-focused coping strategies, and when his or her brother or sister with an ASD had higher levels of functional independ- ence. In interpreting these findings, we speculate that greater similarity among siblings (i.e., in education level and functional abilities) might promote sib- ling closeness.

MRDD Research Reviews DOI 10.1002/mrdd � ASD SIBLINGS � Orsmond and Seltzer 317

To summarize, there is only a lit- tle research describing sibling relation- ships during adulthood when one sib- ling has an ASD. The available data suggest relatively lower levels of engage- ment in the sibling relationship during adulthood, especially compared with siblings of individuals with DS. Given the increasing prevalence rates [Rice, 2007] and the large number of individ- uals with ASDs who will be transition- ing to adulthood over the next several years, there is a great need for more research. At this point, we have only a limited understanding of the extent to which siblings are involved in their brother or sister’s lives, and whether or not they are positioned to take on increased caregiving responsibilities as their parents age and ultimately die.

Sibling Well-Being Similar to the research on sibling

relationships in adulthood, only a few studies have examined sibling well- being exclusively in adults. Some studies have included siblings of various ages, spanning childhood through adulthood, and these are included in this section.

There is some evidence of social and emotional difficulties in siblings of individuals with an ASD during adult- hood. Smalley and Asarnow [1990] found that siblings (mean age of 25) of individuals with autism showed greater impairments in facial emotion recogni- tion than siblings of individuals with no disability, supporting impairments in line with the BAP. Similarly, Piven et al. [1997] reported higher rates of social impairments (33%) in siblings who had more than one brother or sis- ter with autism compared with siblings of children with a brother or sister with DS (0%).

In another study, Piven et al. [1989] used family history methods with 67 adult siblings (average age of 33 years) and found that 15% of the sample had received treatment for depression or mania, which they reported to be con- siderably higher than rates reported in epidemiological studies (roughly 3% of the general population). Other studies also suggest higher rates of affective dis- order than in the general population [DeLong and Dwyer, 1988; Smalley et al., 1995].

In our own research, we exam- ined the incidence of diagnosed disabil- ities in a sample of 117 siblings (mean age of 21 years) in our longitudinal study of families of adolescents and adults with autism [Seltzer et al., 2003]. The most frequent disabilities in siblings

were attention and hyperactivity disor- ders (4.6%), ASDs (2.4%), and psychiat- ric disorders (2.1%) [Orsmond et al., 2007]. Only ASDs were elevated com- pared with the general population. We also found that the presence of disability in multiple siblings was associated with poorer maternal well-being [Orsmond et al., 2007].

To summarize, as in other age groups, the research presents mixed results as to whether siblings of individ- uals with an ASD have poorer well- being during adulthood as compared with their age peers. Although some researchers have found elevated rates of psychological distress, we have not found such in our research. These dif- ferences are likely attributable to differ- ent samples (e.g., community, clinical, multiple incidence families) and also differences in the measures and methods employed.

SUMMARY AND AGENDA FOR FUTURE RESEARCH

Reviewing the literature on sib- lings of individuals with an ASD from a developmental perspective helps us to understand at which points in the life course siblings may be at greater risk, and how the sibling relationship and sibling well-being may change over time. With regard to this latter point, there are very few longitudinal studies, and thus inferences about age-related differences based on cross-sectional comparisons must remain tentative. Some of the patterns observed at differ- ent life stages may be due to cohort effects. For example, the adult siblings reported in the studies to date grew up in a time when there were relatively fewer services and less developed educa- tional programs for children with au- tism. Their experiences were likely dif- ferent from those of younger siblings in recent studies. Thus, our first suggestion is for more longitudinal research. Cross- sequential designs may also be fruitful as they control for both time and cohort effects. Using such approaches will be the only way to truly understand how the sibling relationship and sibling well- being change over time when one sib- ling has an ASD. Understanding sibling relationships from a developmental per- spective is complicated, however, as one needs to take into account and measure developmental changes in the sibling, his or her brother or sister with the dis- ability, and other life course changes in the family.

Second, understanding the devel- opment of siblings of individuals with

an ASD is complicated by the inclusion of a wide age range in the samples of many studies. The risk of psychological and psychiatric problems generally increases in late adolescence and early adulthood [APA, 2000], and thus including siblings in samples ranging from childhood through adulthood may obscure true age-specific prevalence rates. Furthermore, there is considerable literature on the changes in sibling and family relationships from childhood through adulthood [White, 2001; Parke, 2004]. Thus, we recommend that future research on siblings should take a life course developmental approach, consid- ering the context of the life stage of the sibling and the unique risks for the sib- ling relationship and sibling well-being associated with each life stage.

Third, another challenge to understanding continuities and disconti- nuities in the sibling relationship has to do with measurement. The methodolo- gies used in the studies are obviously dependent upon the skills and develop- ment of the sibling. The research on siblings in infancy and young childhood is dependent upon observational meas- ures and parent report. Self-report is of- ten employed during adolescence or adulthood. As Rossiter and Sharpe [2001] observed, the findings varied by the measurement method employed. Moreover, the siblings’ own under- standing and ability to evaluate aspects of the sibling relationship and their well-being change over time.

Fourth, the variability noted in both the sibling relationship and sibling well-being at each life stage suggests that we need to pay greater attention to understanding factors that put siblings at greater risk or, alternatively, that serve as protective factors across the life course. Some of the inconsistent find- ings across studies may be due to differ- ent sample characteristics, methods for data collection, and measures. Attempts towards greater consistency in methods across studies will allow for more appropriate direct comparisons and more accurate information regarding the well-being and sibling relationship when one sibling has an ASD.

Moroever, this variability in find- ings suggests that there may be unmeas- ured factors that are influencing the sibling relationship and well-being. Par- alleling the research on sibling relation- ships in TD individuals, the research on the impact of disability on the siblings has moved from descriptive to explana- tory research. Researchers have begun to examine the important influences of

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factors such as marital stress and coping on the sibling relationship when one sibling has autism [e.g., Rivers and Stoneman, 2003; Ross and Cuskelly, 2006]. Further research along these lines will help us better understand the influ- ences that might be altered through support or intervention to help siblings.

Another factor that has the poten- tial to influence sibling well-being and the sibling relationship is the genetic predisposition siblings may have to the BAP. As Bauminger and Yirmiya [2001] suggest, a genetic predisposition (BAP) may operate as a diathesis (vulner- ability), which under certain stressful environmental conditions, may result in a particular outcome. In our research, we have conducted analyses investigat- ing the interplay between genetic vul- nerability (expressed as the BAP in sib- lings or the mother, family history of ASDs) and stressful family situations (e.g., behavior problems in the brother or sister with ASD) [Orsmond and Selt- zer, 2006]. We found adolescent siblings with a family history of ASD reported significantly more depressive symptoms than those without a family history of ASD. Siblings also were at greater risk of depressive and anxiety symptoms when they had high BAP characteristics and experienced more life events in the past year. Finally, siblings were also at elevated risk for greater anxiety symp- toms when their mothers reported BAP characteristics and higher depressive symptoms (which could act as both a genetic liability and an environmental stress). More research along these lines, examining how biological and environ- mental factors interact to influence sibling well-being and the sibling rela- tionship, will be fruitful in terms of identifying siblings at risk for negative outcomes and for developing interven- tions that promote individual and family well-being.

Other mediating or moderating factors that have been explored in the research reviewed in this article include sibling characteristics (such as gender, birth order, social support, coping, self- concept, and social competence), char- acteristics of the brother or sister with an ASD (such as age, gender, level of functioning), and other family charac- teristics (such as family size, socioeco- nomic status, the parental marital rela- tionship, parental preferential treatment of siblings). For almost all of these fac- tors there are contradictory findings. Furthermore, it is impossible to deter- mine, at this point, which factors are more important at which life stages.

Moreover, studies of siblings of individ- uals with an ASD have been conducted almost exclusively with Caucasian fami- lies in the Western countries. More attention paid to cultural influences will be important in understanding the sib- ling relationship and sibling well-being in this context.

Finally, as Bauminger and Yirmiya [2001] point out, a major impediment to reaching firm conclusions about the sibling relationship and sibling well- being when one sibling has an ASD is the use of different comparison groups in different studies. Many studies com- pare siblings of individuals with an ASD with siblings of individuals with DS, which controls for environmental effects (e.g., the stress of growing up with a sibling with a disability). Few studies have used comparison groups with known complex genetic liabilities, such learning disabilities or psychiatric con- ditions. In addition, few studies have sought to identify variables and mecha- nisms that put siblings of individuals with an ASD at elevated risk.

To conclude, the limited literature about siblings of individuals with an ASD across the life course suggests an elevated risk of negative well-being out- comes and poorer relationships. How- ever, this pattern is tempered by find- ings suggesting positive relationship quality. Nevertheless, the well-being outcomes are danger signals that should be taken seriously, as these siblings are in line to inherit the responsibility for long-term family caregiving from their parents. These results call for not only more research but also more clinical and support services for siblings of indi- viduals with an ASD. n

REFERENCES Achenbach TM, Rescorla LA. 2001. Manual for

ASEBA school-age forms and profiles. Burlington, VT: University of Vermont, Research Center for Children, Youth, and Families.

Akiyama H, Elliot K, Antonucci TC. 1996. Same-sex and cross-sex relationships. J Ger- ontol: Psychol Sci B 51:P374–P382.

American Psychiatric Association. 2000. Diagnos- tic and statistical manual of mental disorders, 4th ed., text revision. Washington, DC: American Psychiatric Association.

Bailey A, Le Couteur A, Gottesman I, et al. 1995. Autism as a strongly genetic disorder: evidence from a British twin study. Psychol Med 25:63–77.

B€agenholm A, Gillberg C. 1991. Psychosocial effects on siblings of children with autism and mental retardation: a population-based study. J Ment Defic Res 35:291–307.

Bauminger N, Yirmiya N. 2001.The functioning and well-being of siblings of children with autism: behavioral-genetic and familial con-

tributions. In: Burack JA, Charman T, Yir- miya N, Zelazo PR, editors. The develop- ment of autism: Perspectives from theory and research. Mahwah, NJ: Lawrence Erlbaum Associates, Publishers. p 61–80.

Brody GH. 1998. Sibling relationship quality: its causes and consequences. Annu Rev Psychol 49:1–24.

Brody GH. 2004. Siblings’ direct and indirect contributions to child development. Curr Dir Psychol Sci 13:124–126.

Cicirelli VG. 1995. Sibling relationships across the life span. New York: Plenum Press.

Constantino JN, Lajonchere C, Lutz M, et al. 2006. Autistic social impairment in the sib- lings of children with pervasive developmen- tal disorders. Am J Psychiatry 163:294–296.

DeLong GR, Dwyer JT. 1988. Correlation of family history with specific autistic sub- groups: asperger’s syndrome and bipolar affective disease. J Autism Dev Disord 18:593–600.

Dierker LC, Albano AM, Clarke GN, et al. 2001. Screening for anxiety and depression in early adolescence. J Am Acad Child Ado- lesc Psychiatry 40:929–936.

Dorris L, Espie CAE, Knott F, et al. 2004. Mind- reading difficulties in the siblings of people with Asperger’s syndrome: evidence for a genetic influence in the abnormal develop- ment of a specific cognitive domain. J Child Psychol Psychiatry 45:412–418.

Dunn J, Slomkowski C, Beardsall L. 1994. Sibling relationships from the preschool period through middle childhood and early adoles- cence. Dev Psychol 30:315–324.

Fisman S, Wolf L, Ellison D, et al. 1996. Risk and protective factors affecting the adjust- ment of siblings of children with chronic disabilities. J Am Acad Child Adolesc Psy- chiatry 35:1532–1541.

Fisman S, Wolf L, Ellison D, et al. 2000. A longi- tudinal study of siblings of children with chronic disabilities. Can J Psychiatry 45: 369–375.

Ferrari M. 1984. Chronic illness: psychosocial effects on siblings. I. Chronically ill boys. J Child Psychol Psychiatry 25:459–476.

Freedman RI, Krauss MS, Seltzer MM. 1997. Aging parents’ residential plans for adult children with mental retardation. Ment Retard 35:114–123.

Gold N. 1993. Depression and social adjustment in siblings of boys with autism. J Autism Dev Disord 23:147–163.

Goldberg WA, Jarvis KL, Osann K, et al. 2005. Brief report: early social communication behaviors in the younger siblings of children with autism. J Autism Dev Disord 35: 657–664.

Greenberg JS, Seltzer MM, Orsmond GI, et al. 1999. Siblings of adults with mental illness or mental retardation: current involvement and expectation of future caregiving. Psy- chiatr Serv 50:1214–1219.

Hastings RP. 2003a. Behavioral adjustment of sib- lings of children with autism. J Autism Dev Disord 33:99–104.

Hastings RP. 2003b. Behavioral adjustment of sib- lings of children with autism engaged in applied behavior analysis early intervention programs: the moderating role of social sup- port. J Autism Dev Disord 33:141–150.

Holmes N, Carr J. 1991. The pattern of care in families of adults with a mental handicap: a comparison between families of autistic adults and Down syndrome adults. J Autism Dev Disord 21:159–176.

MRDD Research Reviews DOI 10.1002/mrdd � ASD SIBLINGS � Orsmond and Seltzer 319

Kaminsky L, Dewey D. 2001. Sibling relationships of children with autism. J Autism Dev Dis- ord 31:399–410.

Kaminsky L, Dewey D. 2002. Psychosocial adjust- ment in siblings of children with autism. J Child Psychol Psychiatry 43:225–232.

Kim JY, McHale SM, Wayne Osgood D, et al. 2006. Longitudinal course and family corre- lates of sibling relationships from childhood through adolescence. Child Dev 77:1746–1761.

Knott F, Lewis C, Williams T. 1995. Sibling interac- tions of children with learning disabilities: a comparison of autism and Down’s syndrome. J Child Psychol Psychiatry 56:965–976.

Kramer L, Kowal AK. 2005. Sibling relationship quality from birth to adolescence: the endur- ing contributions of friends. J Fam Psychol 19:503–511.

Krauss MW, Seltzer MM, Goodman SJ. 1992. Social support networks of adults with men- tal retardation who live at home. Am J Ment Retard 96:432–441.

Krauss MW, Seltzer MM, Gordon R, et al. 1996. Binding ties: the roles of adult siblings of persons with mental retardation. Ment Retard 34:83–93.

Lainhart JE. 1999. Psychiatric problems in indi- viduals with autism, their parents and sib- lings. Int Rev Psychiatry 11:278–298.

Mascha K, Boucher J. 2006. Preliminary investiga- tion of a qualitative method of examining siblings’ experiences of living with a child with ASD. Br J Dev Disabil 52:19–28.

Mates TE. 1990. Siblings of autistic children: their adjustment and performance at home and in school. J Autism Dev Disord 20:545– 553.

Micali N, Chakrabarti S, Fombonne E. 2004. The broad autism phenotype. Autism 8:21–37.

Mitchell S, Brian J, Zwaigenbaum L, et al. 2006. Early language and communication develop- ment of infants later diagnosed with autism spectrum disorder. J Dev Behav Pediatr 27:S69–S78.

Orsmond GI, Lin LY, Seltzer MM. 2007. Mothers of adolescents and adults with autism: the contribution of disability in siblings to maternal well-being and family adjustment. Intellect Dev Disabil 45:257–270.

Orsmond GI, Seltzer MM. 2000. Brothers and sisters of adults with mental retardation: gen- dered nature of the sibling relationship. Am J Ment Retard 105:486–508.

Orsmond GI, Seltzer MM. 2006. Adolescent sib- lings of individuals with autism: a diathesis- stress model of the genetic vulnerability on well-being. Poster presented at the Interna- tional Meeting for Autism Research, Mon- treal, Canada.

Orsmond GI, Seltzer MM. 2007. Siblings of indi- viduals with autism or Down syndrome: effects on adult lives. J Intellect Disabil Res 51:682–696.

Parke R. 2004. Development in the family. Annu Rev Psychol 55:365–399.

Pilowsky T, Yirmiya N, Doppelt O, et al. 2004. Social and emotional adjustment of siblings of children with autism. J Child Psychol Psychiatry 45:855–865.

Piven J, Gayle J, Chase GA, et al. 1989. A family history study of neuropsychiatric disorders in the adult siblings of autistic individuals. J Am Acad Child Adolesc Psychiatry 29: 177–183.

Piven J, Palmer P, Jacobi D, et al. 1997. Broader autism phenotype: evidence from a family history study of multiple-incidence autism families. Am J Psychiatry 154:185–190.

Radloff LS. 1977. The CES-D Scale: a self-report depression scale for research in the general population. Appl Psychol Meas 1:385– 401.

Radloff LS. 1991. The use of the Center for Epi- demiologic Studies Depression Scale in ado- lescents and young adults. J Youth Adolesc 20:149–166.

Reynolds CR, Richmond BO. 1978. What I think and feel: a revised measure of child- ren’s manifest anxiety. J Abnorm Child Psy- chol 6:271–280.

Rice C. 2007. Prevalence of autism spectrum dis- orders–autism and developmental disabilities monitoring network, six sites, United States, 2000. Morb Mortal Wkly Rep 56:1–11.

Ritvo ER. 1985. Concordance for the syndrome of autism in 40 pairs of afflicted twins. Am J Psychiatry 142:74–77.

Rivers JW, Stoneman Z. 2003. Sibling relation- ships when a child has autism: marital stress and support coping. J Autism Dev Disord 33:383–394.

Rodrigue JR, Geffken GR, Morgan SB. 1993. Perceived competence and behavioral adjust- ment of siblings of children with autism. J Autism Dev Disord 23:665–674.

Roeyers H, Mycke K. 1995. Siblings of a child with autism, with mental retardation and with normal development. Child: Care, Health, Dev 21:305–319.

Ross P, Cuskelly M. 2006. Adjustment, sibling problems and coping strategies of brothers and sisters of children with autistic spectrum disorder. J Intellect Dev Disabil 31:77– 86.

Rossiter L, Sharpe D. 2001. The siblings of indi- viduals with mental retardation: a quantita- tive integration of the literature. J Child Fam Stud 10:65–84.

Rutter M. 2000. Genetic studies of autism: from the 1970s into the millennium. J Abnorm Child Psychol 28:3–14.

Seltzer GB, Begun A, Seltzer MM, et al. 1991. Adults with mental retardation and their aging mothers: impacts of siblings. Fam Relat 40:310–317.

Seltzer MM, Greenberg JS, Krauss MW, et al. 1997. Siblings of adults with mental retarda- tion or mental illness: effects on lifestyle and psychological well-being. Fam Relat 46: 395–405.

Seltzer MM, Greenberg JS, Orsmond GI, et al. 2005. Life course studies of siblings of indi- viduals with developmental disabilities. Ment Retard 43:354–359.

Seltzer MM, Krauss MW, Hong J, et al. 2001. Continuity or discontinuity of family involvement following residential transitions of adults who have mental retardation. Ment Retard 39:181–194.

Seltzer MM, Krauss MW, Shattuck PT, et al. 2003. The symptoms of autism spectrum disorders in adolescence and adulthood. J Autism Dev Disord 33:565–581.

Smalley SL, Asarnow RF. 1990. Brief report: cog- nitive subclinical markers in autism. J Autism Dev Disord 20:271–278.

Smalley SL, McCracken J, Tanguay P. 1995. Au- tism, affective disorders, and social phobia. Am J Med Genet 60:19–26.

Smith T, Perry A. 2005. A sibling support group for brothers and sisters of children with au- tism. J Dev Disabil 11:77–88.

Stoneman Z. 2001. Supporting positive sibling relationships during childhood. Ment Retard Dev Disabil Res Rev 7:134–142.

Stoneman Z. 2005. Siblings of children with dis- abilities: research themes. Ment Retard 43: 339–350.

Verte S, Roeyers H, Buysse A. 2003. Behavioural problems, social competence and self-con- cept in siblings of children with autism. Child: Care Health Dev 29:193– 205.

Wassink TH, Brzustowicz LM, Bartlett CW, et al. 2004. The search for autism disease genes. Ment Retard Dev Disabil Res Rev 10: 272–283.

White L. 2001. Sibling relationships over the life course: a panel analysis. J Marriage Fam 63:555–568.

Yirmiya N, Gamliel I, Pilowsky T, et al. 2006. The development of siblings of children with autism at 4 and 14 months: social engagement, communication, and cog- nition. J Child Psychol Psychiatry 47:511– 523.

Yirmiya N, Shaked M, Erel O. 2001. Comparison of siblings of individuals with autism and siblings of individuals with other diagnoses: an empirical summary. In: Schopler E, Yirmiya N, Shulman C, Marcus LM, edi- tors. The research basis for autism interven- tion. Kluwer Academic/Plenum Publishers. p 59–73.

Zwaigenbaum L, Bryson S, Rogers T, et al. 2005. Behavioral manifestations of autism in the first year of life. Int J Dev Neurosci 23:143–152.

320 MRDD Research Reviews DOI 10.1002/mrdd � ASD SIBLINGS � Orsmond and Seltzer