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Factors influencing adjustment in siblings of children with autism spectrum disorders
Research in Autism Spectrum Disorders 5 (2011) 1413–1420
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Factors influencing adjustment in siblings of children with autism spectrum disorders Katherine A. Meyer *, Brooke Ingersoll, David Z. Hambrick Department of Psychology, Michigan State University, East Lansing, MI, USA
A R T I C L E I N F O
A B S T R A C T
Article history: Received 26 January 2011 Accepted 30 January 2011 Available online 25 February 2011
Siblings of children with autism spectrum disorders (ASD) may be at an increased risk of adjustment problems. To examine possible predictors of adjustment difficulties in siblings, 70 mothers with at least one child with ASD and one typical child completed surveys of symptom severity in the child with ASD, impact of the child with ASD on the sibling, maternal depression, and broader autism phenotype (BAP) and behavioral adjustment in the typical sibling. A path analysis indicated that symptom severity in the children with ASD was positively associated with adjustment difficulties in the typical siblings; this relationship was mediated by maternal depression, but not sibling impact. Further, greater expression of the BAP in the siblings was associated with more adjustment difficulties, and this relationship was moderated by autism severity in the children with ASD, such that the relationship was stronger at high levels of ASD severity than at lower levels. These findings highlight the importance of assessing functioning of all family members when working with individuals with ASD and their families. ß 2011 Elsevier Ltd. All rights reserved.
Keywords: Autism Sibling adjustment Broader autism phenotype
1. Introduction Previously researchers have suggested that siblings of children with autism spectrum disorders (ASD) may be at increased risk of adjustment problems. However, findings in this area have been inconsistent. Several studies have indicated that siblings of children with ASD experience increased behavioral or emotional problems compared to normative samples and siblings of typically developing children or children with other developmental disabilities (Gold, 1993; Hastings, 2003a; Rodrigue, Geffken, & Morgan, 1993; Ross & Cuskelly, 2006; Verte´, Roeyers, & Buysse, 2003). However, some studies have found no difference between siblings of children with ASD and other groups (Kaminsky & Dewey, 2002; Pilowsky, Yirmiya, Doppelt, Gross-Tsur, & Shalev, 2004), while others have reported mixed findings (Fisman et al., 1996; Macks & Reeve, 2007; Petalas, Hastings, Nash, Lloyd, & Dowey, 2009). For example, Macks and Reeve (2007) found that having a sibling with ASD enhanced psychosocial well-being when demographic risk factors were limited, but was detrimental when more risk factors were present. Given these contradictory findings, it is important to consider factors that may influence the relationship between having a sibling with ASD and adjustment problems (Orsmond & Seltzer, 2007). One factor that may affect sibling adjustment is the level of impairment of the child with ASD. Qualitative research suggests that typically developing siblings perceive behavior problems such as aggression and acting out in their siblings with ASD to be problematic and embarrassing in their daily lives (Mascha & Boucher, 2006). Indeed, symptom severity and behavior problems in the child with ASD have been found to be positively associated with adjustment difficulties in typically developing siblings both concurrently and over time (Benson & Karlof, 2008; Hastings, 2003b, 2007).
* Corresponding author at: 69F Psychology Building, Michigan State University, East Lansing, MI 48824, USA. Tel.: +1 517 432 8031. E-mail address: [email protected] (K.A. Meyer). 1750-9467/$ – see front matter ß 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.rasd.2011.01.027
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While autism severity may have a direct impact on sibling adjustment (e.g., exposure to more severe symptoms increases sibling stress), it is also important to examine factors that may mediate or moderate this relationship. One possible mediator is the impact of the child with ASD on the sibling’s daily life. Mascha and Boucher (2006) found that the concerns of siblings of children with ASD include difficulties interacting with their sibling, behavior problems such as aggression in their sibling, feelings of embarrassment, difficulties explaining the disability, and increased household responsibility. These problems may be greater when the child with ASD is more severely affected and may lead to increased emotional and behavioral difficulties in the typical sibling. Another possible mediator of the relationship between ASD severity and sibling adjustment difficulties is maternal depression. Studies have found that the degree of impairment in the child with ASD is positively correlated with maternal depression (e.g., Baker-Ericzen, Brookman-Frazee, & Stahmer, 2005; Benson, 2006; Davis & Carter, 2008). In addition, a large literature indicates that maternal depression has adverse effects on child mental health (see Downey & Coyne, 1990 for review). While the relationship between maternal depression and child mental health may be partially accounted for by shared genetic risk factors, models of risk transmission of maternal depression propose that experiential factors such as exposure to the parent’s negative behaviors, cognitions, and affect also play a significant role in the elevated risk for children of depressed mothers (Goodman & Gotlib, 1999). Anotherfactorthatmaycontributetoincreasedadjustmentdifficultiesisthepresenceofthebroaderautismphenotype(BAP)in siblingsofchildrenwithASD(Bauminger&Yirmiya,2001;Orsmond&Seltzer,2007).TheBAPisasubclinicalsetofpersonalitytraits and social, cognitive, and language deficits often found in family members that are thought to represent a familiality or genetic liability for ASD (e.g., Bailey, Palferman, Heavey, & Le Couteur, 1998). Although limited research has directly examined this possibility, a number of studies have found that siblings of children with ASD are more likely to have subtle cognitive, language, academic,andsocialinteractiondeficitsthansiblingsoftypicallydevelopingchildren(e.g.,Ben-Yizhaketal.,inpress;Constantino etal.,2006;Gamliel,Yirmiya,Jaffe,Manor,&Sigman,2009).Asthesedeficitsareindependentriskfactorsforadjustmentproblemsin children more generally (Constantino, Hudziak, & Todd, 2003), these findings suggest a possible link between the BAP and adjustment problems in siblings with ASD. It is also possible that the presence of the BAP in siblings interacts with environmental stressors to increase the risk for adjustment problems. For example, Orsmond and Seltzer (2009) found that BAP characteristics in adolescent sisters of children with ASD interacted with negative life events to predict depression and anxiety symptoms. These findings suggest that the BAP may be a significant risk factor for adjustment difficulties in siblings of children with ASD. The goal of this study was to examine the relationship between child autism severity, sibling BAP, and adjustment problems in siblings of children with ASD. In particular, we examined whether child autism severity and sibling BAP predicted adjustment problems in siblings, and whether negative impact on the sibling and maternal depression mediated or moderated the effect of child autism severity on sibling adjustment. We also examined whether child autism severity, maternal depression, or impact on the sibling moderated the effect of sibling BAP on adjustment problems. We predicted that child autism severity would be related to sibling adjustment problems, primarily through its impact on the sibling’s daily life and maternal depression. Further, we predicted that the BAP would be directly associated with adjustment problems in the siblings, a relationship that might be moderated by other family factors such as maternal depression or child autism severity. 2. Methods 2.1. Participants and procedure Participants were 90 mothers who had at least one biological child aged 2–18 with an ASD and at least one typically developing child aged 6–18. In order to obtain information on sibling dyads at a variety of ages and birth orders, mothers of children with ASD who had more than one typically developing sibling in the targeted age range were instructed to report on a typically developing sibling of their choice. Participants were recruited using the Interactive Autism Network (IAN) Research Database. IAN is a free online service that links individuals with ASD and their families with ongoing research projects. To register as a research participant, children must have received an ASD diagnosis from a professional and parents must complete a number of questionnaires regarding their child’s diagnosis, history, and ASD symptoms. Eligible participants were recruited via an e-mail that explained the purpose of the study and included a link to the online survey. All data were collected anonymously. Missing data were excluded case-wise, yielding 70 participants who completed all measures in the survey (78% completion rate). 2.2. Measures 2.2.1. Child autism severity The Autism Behavior Checklist (ABC; Krug, Arick, & Almond, 1980) is a 57-item parent-report questionnaire that asks about common symptoms of ASD and associated behavior problems. Items are weighted in importance and summed for a total score ranging from 0 to 156, with higher scores representing more severe autistic symptomatology. 2.2.2. Impact on sibling The Family Impact Questionnaire (FIQ; Donenberg & Baker, 1993) is a 50-item parent report measure that asks parents to answer questions about the impact of their child on the family compared to other children of the same age. For this study, we
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used only the 9-item ‘‘impact on siblings’’ subscale of the FIQ. This subscale includes questions about the sibling relationship and about child behaviors that impact siblings. Scores on the FIQ-siblings subscale range from 0 to 27, with higher scores indicating more negative impact of the child on his/her sibling. 2.2.3. Maternal depressive symptoms The Center for Epidemiological Studies-Depression Scales (CES-D; Radloff, 1977) is a 20-item self-report scale designed to measure depressive symptoms in the general population. Respondents rate how often they have experienced each symptom over the past week on a 4-point scale. Total scores on the CES-D can range from 0 to 60, with higher scores indicating more depressive symptoms. 2.2.4. Sibling broader autism phenotype The Social Responsiveness Scale (SRS; Constantino, 2002) is a 65-item parent report questionnaire that asks parents to rate their child on a Likert-type scale about a variety of behaviors characteristic of ASD. This scale been used to identify children at risk for ASD as well as measure severity of symptoms of autism in children with and without a diagnosis of ASD. Scores are converted to T-scores and higher scores suggest a greater number of symptoms of autism. 2.2.5. Sibling behavioral adjustment The Strengths and Difficulties Questionnaire (SDQ; Goodman, 1997) is a 25-item parent-report questionnaire designed as a brief behavioral screener. Parents answer each item as ‘‘Not true,’’ ‘‘Somewhat true,’’ or ‘‘Certainly true’’ with regard to the child. Each item is scored 0–2 and item scores are summed. The SDQ includes five subscales: (1) emotional symptoms, (2) conduct problems, (3) hyperactivity/inattention, (4) peer relationship problems, and (5) prosocial behavior. The first four scales can be summed to obtain a Total Problems Score, which ranges from 0 to 40, with higher scores indicating more problems. The Total Problems Score was used as a measure of siblings’ behavioral adjustment. Table 1 Sample demographics. Variables Parent age Parent race/ethnicity White Black Hispanic Asian Native American Maternal education level Some high school High school diploma Some college/specialized training 4-Year college degree Graduate degree Marital status Married Not married Annual family income $24,999 or less $25–$49,999 $50–$74,999 $75–$99,999 $100,000 or more Child with ASD age Child with ASD gender Male Female Child with ASD diagnosis Autistic disorder/autism PDD-NOS Asperger’s syndrome Other ASD Sibling age Sibling gender Male Female Sibling birth order Typical sibling younger Typical sibling older Same age
Mean (SD)/percent of sample N = 70 40.7 (6.7) 94% 3% 3% 0% 0% 3% 4% 32% 41% 20% 80% 20% 6% 21% 27% 18% 28% 9.5 (3.8) 86% 14% 52% 20% 25% 3% 10.5 (3.6) 49% 51% 44% 51% 5%
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2.3. Statistical analysis We performed a path analysis with sibling adjustment as the outcome variable, and child autism severity and sibling BAP as predictor variables. Child’s impact on the sibling and maternal depression were entered as possible mediators of the relationship between child autism severity and sibling adjustment. Missing item-level data (0.0004% of total data) were multiply-imputed five times. In this analysis, mediation would be indicated by a statistically significant effect of a predictor variable (e.g., child autism severity) on a mediator variable (e.g., maternal depression) and of that mediator variable on sibling adjustment, along with a non-significant effect of the predictor variable on sibling adjustment (i.e., a non-significant direct effect). Partial mediation would be indicated by a significant indirect effect along with a significant direct effect. We also performed a series of regression analyses to test for possible moderator effects (i.e., interactions). Specifically, we tested for interactions between the predictor variables (child autism severity, sibling BAP) and the hypothesized mediator variables (maternal depression and impact on sibling) in predicting sibling adjustment. In addition, we tested whether the two predictor variables interacted with each other to predict sibling adjustment. 3. Results 3.1. Descriptive statistics and normative comparisons Descriptive statistics for sociodemographic variables are reported in Table 1. Regarding normative comparisons for the measures used, there are three points of interest. First, the mean score of the typically developing siblings on the SDQ was 10.3 (SD = 7.3, range = 0–27). A one-sample t-test indicated that this mean was significantly higher than the mean for American children (t = 3.64, p = .001) in the normative sample (Centers for Disease Control, 2001). Notably, 25.4% of siblings scored above the recommended clinical cutoff of 17 on this scale. Second, the mean score of mothers on the CES-D was 17.8 (SD = 12.7, range = 0–55), which was significantly higher than the mean of 9.25 reported in the initial normative sample (t = 5.63, p < .001) and 52.1% of mothers (as compared to 19% of participants in the normative sample) scored at or above the clinical cutoff of 16 (Radloff, 1977). Finally, the mean T-score of typically developing siblings on the SRS was 51.51 (SD = 15.8). This mean was not significantly different from the mean T-score of 50 in the normative sample (t = .80, p > .10). 3.2. Path analysis The results of the path analysis are shown in Fig. 1 (see Table 2 for zero-order correlations). All correlations not predicted by our theoretical model were tested in the path model and found to be nonsignificant. They were subsequently trimmed from the model. It can be seen that child symptom severity was a positive predictor of maternal depressive symptoms (.58), which in turn was a positive predictor of sibling adjustment problems (.23). Child symptom severity was also a positive predictor of the child with ASD’s impact on siblings (.47), but sibling impact did not significantly predict sibling adjustment
[()TD$FIG]
Sibling Broader Ausm Phenotype Maternal Depression .23
.58 Child with ASD Ausm Severity
.02
.47
.50
Sibling Adjustment Problems .18
Child with ASD Impact on Siblings Solid Line: Significant path Dashed Line: Non-significant path Fig. 1. Path analysis testing for direct and indirect effects of Autism Spectrum Disorder (ASD) severity in the child with autism on adjustment problems in the typical sibling. Non-predicted correlations (based on the theoretical model) were found to be nonsignificant and were trimmed from the final model. Cross refer Table 2 for zero-order correlations between all study variables.
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Table 2 Correlation matrix. Autism severity Autism severity Sibling BAP Maternal depression Impact on siblings Sibling adjustment problems
(.88)
Sibling BAP .08 (.97)
Maternal depression **
Impact on siblings **
.27* .56** .38** .37** (.87)
.47 .22 .34** (.77)
.58 .17 (.94)
Sibling adjustment problems
Note: Cronbach’s alphas for each variable are depicted in parentheses along the diagonal. * p < .05. ** p < .01.
problems. As shown in Table 3, approximately 91% of the relationship between child autism severity and sibling adjustment was mediated through maternal depression and impact on siblings. That is, the total indirect effect of child autism severity on sibling adjustment involving these two mediators (the sum of the indirect effects) was 91% of the total effect of child autism severity (the sum of the direct and indirect effects) on sibling adjustment (i.e., .21/.23 100 = 91%). Furthermore, maternal depression was the more important of the two mediators, as it accounted for approximately 57% of the relationship between child autism severity and sibling adjustment (i.e., .13/.23 100 = 57%), compared to 35% for impact on siblings (i.e., .08/ .23 100 = 35%). Finally, the BAP in siblings was a direct positive predictor of adjustment difficulties (.50). Relationships between all other variables were nonsignificant. Overall, this model accounted for 37.3% of the variance in sibling adjustment. 3.3. Moderator analyses We performed regression analyses to test for statistical interactions between pairs of predictor variables in the model shown in Fig. 1 (cf. Cohen, Cohen, West, & Aiken, 2003). In each analysis, we entered the two predictor variables (meancentered) in the first step, and an interaction term in the second step (i.e., the product of the predictors). Our specific questions were; (1) does child autism severity interact with maternal depression or impact on sibling to predict sibling adjustment; (2) does sibling BAP interact with maternal depression or impact on sibling to predict sibling adjustment; (3) do child autism severity and sibling BAP interact with one another to predict sibling adjustment? Results are shown in Table 4. As can be seen, there was a significant interaction between sibling BAP and child autism severity on sibling adjustment, R2 = .45, b = .29, F = 9.3, p < .01. As can be seen in Fig. 2, there was a stronger positive
Table 3 Summary of direct and indirect effects of child symptom severity, maternal depression, and impact on siblings on sibling adjustment. Sibling adjustment (SDQ) Child symptom severity (ABC) direct effect !Indirect effect: parent depression (CES-D) !Indirect effect: impact on siblings (FIQ) Total effect Percent indirect effect (total) !Percent indirect effect: parent depression !Percent indirect effect: impact on siblings
.02 .13* .08 .23 91% 57% 35%
(.58 .23 = .13) (.47 .18 = .08) (.21/.23 = 91%) (.13/.23 = 57%) (.08/.23 = 35%)
Note: Coefficients for predictor ! mediator path and mediator ! outcome path were multiplied to obtain value for indirect effect, and direct and indirect effects were summed to obtain value for total effect (an indirect effect is assumed to be statistically significant if both of these effects are significant; cf. Kline, 2005). Strengths and Difficulties Questionnaire (SDQ); Autism Behavior Checklist (ABC); Center for Epidemiological Studies-Depression Scales (CESD); Family Impact Questionnaire (FIQ). * p < .05.
Table 4 Results of tests for statistical interactions in regression analyses.
Autism severity impact on sibling Autism severity maternal depression Sibling BAP impact on sibling Sibling BAP maternal depression Autism severity sibling BAP *
p < .01.
Inc. R2
F1,66
b
.17 .16 .40 .42 .45
1.87 1.21 2.57 2.74 9.28*
.16 .14 .16 .17 .29
[()TD$FIG]
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25
Sibling Adjustment Difficules
High Ausm Severity Low Ausm Severity 20
15
10
5
0 Low
High
Sibling Broader Ausm Phenotype Fig. 2. Predicted values for sibling adjustment (Strengths and Difficulties Questionnaire) for low vs. high levels of autism severity in the child with autism (Autism Behavior Checklist) and broader autism phenotype in the sibling (Social Responsiveness Scale).
relationship between BAP in the sibling and sibling adjustment at high levels of ASD severity than at lower levels. No other interactions were significant (Fs < 3). 4. Discussion Siblings of children with ASD exhibited higher rates of adjustment problems than children in the normative sample. This finding is consistent with reports suggesting that siblings of children with ASD may be at an increased risk of adjustment problems. Similarly, mothers of children with ASD reported significantly higher rates of depressive symptoms than the normative sample. Again, this finding is consistent with research indicating an increased risk of depression in mothers of children with ASD. Our findings suggest two possible mechanisms by which siblings of children with ASD may be at heightened risk for adjustment difficulties. First, siblings of children with more severe ASD symptoms were more likely to exhibit adjustment difficulties. This finding is consistent with other studies that have found relationships between autism severity and behavior problems of children with ASD and adjustment difficulties in their typically developing siblings (Benson & Karlof, 2008; Hastings, 2003b, 2007). However, we found that this relationship was fully mediated by maternal depressive symptoms. Thus, our results do not support the idea that child autism severity affects sibling adjustment directly. Rather, the relationship is likely influenced by increased rates of depressive symptoms in mothers of more severely affected children with ASD, a finding which is consistent with research indicating detrimental effects of maternal depression on children (Downey & Coyne, 1990). A parent who is experiencing significant levels of depressive symptoms (potentially as a result of parenting a child with severe ASD symptoms) may be less effective in balancing the demands of multiple children with different developmental needs and may be less adept at providing both necessary emotional support and effective discipline. In addition, a depressed parent may model less adaptive coping styles that are then adopted by their typically developing children. Interestingly, although the impact of the child with ASD on the sibling was associated both with child autism severity and with sibling adjustment, it did not mediate the relationship between these two variables in the path analysis. This may be partially explained by the observed positive correlation between sibling impact and maternal depression (a correlation between the two mediator variables in the path model reduces the variance explained by each independent predictor). It is possible that mothers who are experiencing more depressive symptoms allow the child with ASD to have a greater impact of the sibling’s life. For example, depressed mothers may have less energy to attend to the sibling’s social/emotional needs or may monitor the child with ASD less closely, leading to negative behaviors such as aggression toward the sibling. Second, siblings of children with ASD who exhibit a greater number of BAP characteristics may be more likely to have adjustment difficulties. Further, this relationship appears to be moderated by autism severity in the child with autism. While the siblings in this sample did not score above average on our measure of BAP as a group, approximately 23% of siblings scored in the at-risk or clinical range for an ASD diagnosis, suggesting that many of the siblings in our sample were experiencing a significant number of characteristics of autism. Siblings who exhibit characteristics associated with the BAP, such as social difficulties and maladaptive personality traits, may be less likely to seek social support when needed and more likely to react negatively to the stress of having a sibling with ASD or other stressful life events. Having a sibling with more severe ASD characteristics and general behavior problems (the Autism Behavior Checklist measures both symptoms specific to autism and general behavioral problems such as tantrums and aggression) may serve as one such stressor for siblings of children with ASD. While siblings who themselves exhibit few ASD traits may be able to relate to and empathize with a
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sibling at any functioning level, relating to a lower-functioning sibling may be more difficult for siblings who have difficulties with important skills such as social relatedness, empathy, and emotional awareness. This finding is consistent with previous research indicating that siblings with more BAP characteristics are more likely to develop depression and anxiety in response to stressful life events (Orsmond & Seltzer, 2009). To our knowledge, this is the first study to find a direct relationship between the BAP and adjustment difficulties in siblings of children with ASD. This study has several limitations. First, although evidence suggests that internet parent report of ASD status is valid (Rosenberg et al., 2009), we were unable to confirm the ASD diagnoses in the ASD sample or rule out an ASD diagnosis in the typically developing siblings. While we have only one measure of ASD symptoms in the sibling with autism (the ABC), the mean ABC score in the children with autism in this sample was 59.2 (SD = 27.8). This score falls well above the cutoff score for autism that Wadden, Bryson, and Roger (1991) reported to best discriminated autism from non-autism groups on the ABC. In addition, the Interactive Autism Network (IAN), from which the families in this study were recruited, asks parents to fill out a variety of diagnostic questionnaires for the children with ASD. While we do not have access to the scores of specific children in our sample on these measures, Lee, Marvin, Watson, Piggot, and Law (2010) found that 98% of a group of children representative of the overall pool of participants in the IAN network were ASD-positive based on clinician’s best estimate, with 99% scoring ASD-positive based on the Autism Diagnostic Interview-Revised and 93% scoring ASD-positive based on direct observational assessment. These data indicate that the great majority of children involved in the IAN subject pool do have ASD diagnoses. Finally, it is important to note that while the diagnoses of the children in this study were not confirmed by investigators (and thus it is possible that the sample includes some children who do not meet full criteria for ASD), the families in this study are self-identifying as having a child with ASD. Families of children with ASD who are accessing the family-related services in the community where these findings are likely to be most applicable (e.g., parent or sibling support groups) are those who self-identify as having a child with ASD. Therefore, including these families in this type of research may increase the ecological validity of the findings. However, future research that can replicate these findings in a group of families whose diagnoses are confirmed by the investigators is an important next step. Second, because all data were collected from the children’s mothers, it is possible that the relationships between the different measures in this study were influenced by overall positive or negative reporting biases of individual mothers. In particular, high levels of maternal depression might lead to a negative reporting bias on measures of child functioning for both children (Fergusson, Lynskey, & Horwood, 1993). However, Davis and Carter (2008) found that parental depression may affect parental appraisal of child behavior less in families of children with ASD than families of typically developing children. Nevertheless, it is important for future research to obtain data from multiple informants, including the typically developing siblings, to ensure that the relationships found in this study were not primarily due to response bias of a single reporter. Third, our sample consisted primarily of families from Caucasian, highly educated, married, and middle- to high-income households. Therefore, the findings of this study cannot be generalized to all families with a child with ASD. Finally, as the data in this study were cross-sectional, the direction of effect of the associations cannot be determined. Thus, future research that uses longitudinal designs with families with a wider range of racial, ethnic, and socioeconomic backgrounds is needed. These findings have important implications for the assessment and treatment of family members of individuals with ASD and stress the need for a family-level approach to treating difficulties in these families. First, given the high rates of maternal depression and sibling adjustment difficulties found in this study, particularly among family members of severely affected individuals with ASD, it is important for those who treat people with ASD (e.g., teachers, psychologists, physicians) to be alert for potential difficulties in other family members in order to provide needed support or make appropriate referrals. These findings also stress that characteristics of the sibling with autism, the typically developing sibling, and the mother may all interact to contribute to adjustment difficulties in typically developing siblings. Thus, treatments or support groups that include the entire family may be more effective for these siblings than individual treatments that do not address the characteristics and needs of the entire family. In sum, our findings suggest that adjustment problems in siblings of children with ASD are related both to increased symptom severity in the child with ASD, via its effect on maternal depressive symptoms, and the expression of a greater number of characteristics of autism in the siblings themselves. Further, greater expression of autism characteristics in the siblings was most detrimental to sibling adjustment when the child with ASD had more severe symptoms. 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Siblings of individuals with autism spectrum disorders across the life course. Mental Retardation and Developmental Disabilities Research Reviews, 13, 313–320. Orsmond, G., & Seltzer, M. (2009). Adolescent siblings of individuals with an autism spectrum disorder: Testing a diathesis-stress model of sibling well-being. Journal of Autism and Developmental Disorders, 39, 1053–1065. Petalas, M. A., Hastings, R. P., Nash, S., Lloyd, T., & Dowey, A. (2009). Emotional and behavioural adjustment in siblings of children with intellectual disability with and without autism. Autism, 13, 471–483. Pilowsky, T., Yirmiya, N., Doppelt, O., Gross-Tsur, V., & Shalev, R. S. (2004). Social and emotional adjustment in siblings of children with autism. Journal of Child Psychology and Psychiatry, 45, 855–865. Radloff, L. S. (1977). The CES-D scale: A self-report depression scale for research in the general population. Applied Psychological Measurement, 1, 385–401. Rodrigue, J. R., Geffken, G. R., & Morgan, S. B. (1993). Perceived competence and behavioral adjustment of siblings of children with autism. Journal of Autism and Developmental Disorders, 23, 665–674. Rosenberg, R. E., Law, J. K., Yenokyan, G., McGready, J., Kaufmann, W. E., & Law, P. A. (2009). Characteristics and concordance of autism spectrum disorders among 277 twin pairs. Archives of Pediatrics & Adolescent Medicine, 163(10), 907–914. Ross, P., & Cuskelly, M. (2006). Adjustment, sibling problems, and coping strategies of brothers and sisters of children with autistic spectrum disorder. Journal of Intellectual and Development Disability, 31, 77–86. Verte´, S, Roeyers, H., & Buysse, A. (2003). Behavioural problems, social competence, and self-concept in siblings of children with autism. Child: Care, Health, & Development, 29, 193–205. Wadden, N. P., Bryson, S. E., & Rodger, R. S. (1991). A closer look at the Autism Behavior Checklist: Discriminant validity and factor structure. 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Research in Autism Spectrum Disorders Journal homepage: http://ees.elsevier.com/RASD/default.asp
Factors influencing adjustment in siblings of children with autism spectrum disorders Katherine A. Meyer *, Brooke Ingersoll, David Z. Hambrick Department of Psychology, Michigan State University, East Lansing, MI, USA
A R T I C L E I N F O
A B S T R A C T
Article history: Received 26 January 2011 Accepted 30 January 2011 Available online 25 February 2011
Siblings of children with autism spectrum disorders (ASD) may be at an increased risk of adjustment problems. To examine possible predictors of adjustment difficulties in siblings, 70 mothers with at least one child with ASD and one typical child completed surveys of symptom severity in the child with ASD, impact of the child with ASD on the sibling, maternal depression, and broader autism phenotype (BAP) and behavioral adjustment in the typical sibling. A path analysis indicated that symptom severity in the children with ASD was positively associated with adjustment difficulties in the typical siblings; this relationship was mediated by maternal depression, but not sibling impact. Further, greater expression of the BAP in the siblings was associated with more adjustment difficulties, and this relationship was moderated by autism severity in the children with ASD, such that the relationship was stronger at high levels of ASD severity than at lower levels. These findings highlight the importance of assessing functioning of all family members when working with individuals with ASD and their families. ß 2011 Elsevier Ltd. All rights reserved.
Keywords: Autism Sibling adjustment Broader autism phenotype
1. Introduction Previously researchers have suggested that siblings of children with autism spectrum disorders (ASD) may be at increased risk of adjustment problems. However, findings in this area have been inconsistent. Several studies have indicated that siblings of children with ASD experience increased behavioral or emotional problems compared to normative samples and siblings of typically developing children or children with other developmental disabilities (Gold, 1993; Hastings, 2003a; Rodrigue, Geffken, & Morgan, 1993; Ross & Cuskelly, 2006; Verte´, Roeyers, & Buysse, 2003). However, some studies have found no difference between siblings of children with ASD and other groups (Kaminsky & Dewey, 2002; Pilowsky, Yirmiya, Doppelt, Gross-Tsur, & Shalev, 2004), while others have reported mixed findings (Fisman et al., 1996; Macks & Reeve, 2007; Petalas, Hastings, Nash, Lloyd, & Dowey, 2009). For example, Macks and Reeve (2007) found that having a sibling with ASD enhanced psychosocial well-being when demographic risk factors were limited, but was detrimental when more risk factors were present. Given these contradictory findings, it is important to consider factors that may influence the relationship between having a sibling with ASD and adjustment problems (Orsmond & Seltzer, 2007). One factor that may affect sibling adjustment is the level of impairment of the child with ASD. Qualitative research suggests that typically developing siblings perceive behavior problems such as aggression and acting out in their siblings with ASD to be problematic and embarrassing in their daily lives (Mascha & Boucher, 2006). Indeed, symptom severity and behavior problems in the child with ASD have been found to be positively associated with adjustment difficulties in typically developing siblings both concurrently and over time (Benson & Karlof, 2008; Hastings, 2003b, 2007).
* Corresponding author at: 69F Psychology Building, Michigan State University, East Lansing, MI 48824, USA. Tel.: +1 517 432 8031. E-mail address: [email protected] (K.A. Meyer). 1750-9467/$ – see front matter ß 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.rasd.2011.01.027
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While autism severity may have a direct impact on sibling adjustment (e.g., exposure to more severe symptoms increases sibling stress), it is also important to examine factors that may mediate or moderate this relationship. One possible mediator is the impact of the child with ASD on the sibling’s daily life. Mascha and Boucher (2006) found that the concerns of siblings of children with ASD include difficulties interacting with their sibling, behavior problems such as aggression in their sibling, feelings of embarrassment, difficulties explaining the disability, and increased household responsibility. These problems may be greater when the child with ASD is more severely affected and may lead to increased emotional and behavioral difficulties in the typical sibling. Another possible mediator of the relationship between ASD severity and sibling adjustment difficulties is maternal depression. Studies have found that the degree of impairment in the child with ASD is positively correlated with maternal depression (e.g., Baker-Ericzen, Brookman-Frazee, & Stahmer, 2005; Benson, 2006; Davis & Carter, 2008). In addition, a large literature indicates that maternal depression has adverse effects on child mental health (see Downey & Coyne, 1990 for review). While the relationship between maternal depression and child mental health may be partially accounted for by shared genetic risk factors, models of risk transmission of maternal depression propose that experiential factors such as exposure to the parent’s negative behaviors, cognitions, and affect also play a significant role in the elevated risk for children of depressed mothers (Goodman & Gotlib, 1999). Anotherfactorthatmaycontributetoincreasedadjustmentdifficultiesisthepresenceofthebroaderautismphenotype(BAP)in siblingsofchildrenwithASD(Bauminger&Yirmiya,2001;Orsmond&Seltzer,2007).TheBAPisasubclinicalsetofpersonalitytraits and social, cognitive, and language deficits often found in family members that are thought to represent a familiality or genetic liability for ASD (e.g., Bailey, Palferman, Heavey, & Le Couteur, 1998). Although limited research has directly examined this possibility, a number of studies have found that siblings of children with ASD are more likely to have subtle cognitive, language, academic,andsocialinteractiondeficitsthansiblingsoftypicallydevelopingchildren(e.g.,Ben-Yizhaketal.,inpress;Constantino etal.,2006;Gamliel,Yirmiya,Jaffe,Manor,&Sigman,2009).Asthesedeficitsareindependentriskfactorsforadjustmentproblemsin children more generally (Constantino, Hudziak, & Todd, 2003), these findings suggest a possible link between the BAP and adjustment problems in siblings with ASD. It is also possible that the presence of the BAP in siblings interacts with environmental stressors to increase the risk for adjustment problems. For example, Orsmond and Seltzer (2009) found that BAP characteristics in adolescent sisters of children with ASD interacted with negative life events to predict depression and anxiety symptoms. These findings suggest that the BAP may be a significant risk factor for adjustment difficulties in siblings of children with ASD. The goal of this study was to examine the relationship between child autism severity, sibling BAP, and adjustment problems in siblings of children with ASD. In particular, we examined whether child autism severity and sibling BAP predicted adjustment problems in siblings, and whether negative impact on the sibling and maternal depression mediated or moderated the effect of child autism severity on sibling adjustment. We also examined whether child autism severity, maternal depression, or impact on the sibling moderated the effect of sibling BAP on adjustment problems. We predicted that child autism severity would be related to sibling adjustment problems, primarily through its impact on the sibling’s daily life and maternal depression. Further, we predicted that the BAP would be directly associated with adjustment problems in the siblings, a relationship that might be moderated by other family factors such as maternal depression or child autism severity. 2. Methods 2.1. Participants and procedure Participants were 90 mothers who had at least one biological child aged 2–18 with an ASD and at least one typically developing child aged 6–18. In order to obtain information on sibling dyads at a variety of ages and birth orders, mothers of children with ASD who had more than one typically developing sibling in the targeted age range were instructed to report on a typically developing sibling of their choice. Participants were recruited using the Interactive Autism Network (IAN) Research Database. IAN is a free online service that links individuals with ASD and their families with ongoing research projects. To register as a research participant, children must have received an ASD diagnosis from a professional and parents must complete a number of questionnaires regarding their child’s diagnosis, history, and ASD symptoms. Eligible participants were recruited via an e-mail that explained the purpose of the study and included a link to the online survey. All data were collected anonymously. Missing data were excluded case-wise, yielding 70 participants who completed all measures in the survey (78% completion rate). 2.2. Measures 2.2.1. Child autism severity The Autism Behavior Checklist (ABC; Krug, Arick, & Almond, 1980) is a 57-item parent-report questionnaire that asks about common symptoms of ASD and associated behavior problems. Items are weighted in importance and summed for a total score ranging from 0 to 156, with higher scores representing more severe autistic symptomatology. 2.2.2. Impact on sibling The Family Impact Questionnaire (FIQ; Donenberg & Baker, 1993) is a 50-item parent report measure that asks parents to answer questions about the impact of their child on the family compared to other children of the same age. For this study, we
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used only the 9-item ‘‘impact on siblings’’ subscale of the FIQ. This subscale includes questions about the sibling relationship and about child behaviors that impact siblings. Scores on the FIQ-siblings subscale range from 0 to 27, with higher scores indicating more negative impact of the child on his/her sibling. 2.2.3. Maternal depressive symptoms The Center for Epidemiological Studies-Depression Scales (CES-D; Radloff, 1977) is a 20-item self-report scale designed to measure depressive symptoms in the general population. Respondents rate how often they have experienced each symptom over the past week on a 4-point scale. Total scores on the CES-D can range from 0 to 60, with higher scores indicating more depressive symptoms. 2.2.4. Sibling broader autism phenotype The Social Responsiveness Scale (SRS; Constantino, 2002) is a 65-item parent report questionnaire that asks parents to rate their child on a Likert-type scale about a variety of behaviors characteristic of ASD. This scale been used to identify children at risk for ASD as well as measure severity of symptoms of autism in children with and without a diagnosis of ASD. Scores are converted to T-scores and higher scores suggest a greater number of symptoms of autism. 2.2.5. Sibling behavioral adjustment The Strengths and Difficulties Questionnaire (SDQ; Goodman, 1997) is a 25-item parent-report questionnaire designed as a brief behavioral screener. Parents answer each item as ‘‘Not true,’’ ‘‘Somewhat true,’’ or ‘‘Certainly true’’ with regard to the child. Each item is scored 0–2 and item scores are summed. The SDQ includes five subscales: (1) emotional symptoms, (2) conduct problems, (3) hyperactivity/inattention, (4) peer relationship problems, and (5) prosocial behavior. The first four scales can be summed to obtain a Total Problems Score, which ranges from 0 to 40, with higher scores indicating more problems. The Total Problems Score was used as a measure of siblings’ behavioral adjustment. Table 1 Sample demographics. Variables Parent age Parent race/ethnicity White Black Hispanic Asian Native American Maternal education level Some high school High school diploma Some college/specialized training 4-Year college degree Graduate degree Marital status Married Not married Annual family income $24,999 or less $25–$49,999 $50–$74,999 $75–$99,999 $100,000 or more Child with ASD age Child with ASD gender Male Female Child with ASD diagnosis Autistic disorder/autism PDD-NOS Asperger’s syndrome Other ASD Sibling age Sibling gender Male Female Sibling birth order Typical sibling younger Typical sibling older Same age
Mean (SD)/percent of sample N = 70 40.7 (6.7) 94% 3% 3% 0% 0% 3% 4% 32% 41% 20% 80% 20% 6% 21% 27% 18% 28% 9.5 (3.8) 86% 14% 52% 20% 25% 3% 10.5 (3.6) 49% 51% 44% 51% 5%
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2.3. Statistical analysis We performed a path analysis with sibling adjustment as the outcome variable, and child autism severity and sibling BAP as predictor variables. Child’s impact on the sibling and maternal depression were entered as possible mediators of the relationship between child autism severity and sibling adjustment. Missing item-level data (0.0004% of total data) were multiply-imputed five times. In this analysis, mediation would be indicated by a statistically significant effect of a predictor variable (e.g., child autism severity) on a mediator variable (e.g., maternal depression) and of that mediator variable on sibling adjustment, along with a non-significant effect of the predictor variable on sibling adjustment (i.e., a non-significant direct effect). Partial mediation would be indicated by a significant indirect effect along with a significant direct effect. We also performed a series of regression analyses to test for possible moderator effects (i.e., interactions). Specifically, we tested for interactions between the predictor variables (child autism severity, sibling BAP) and the hypothesized mediator variables (maternal depression and impact on sibling) in predicting sibling adjustment. In addition, we tested whether the two predictor variables interacted with each other to predict sibling adjustment. 3. Results 3.1. Descriptive statistics and normative comparisons Descriptive statistics for sociodemographic variables are reported in Table 1. Regarding normative comparisons for the measures used, there are three points of interest. First, the mean score of the typically developing siblings on the SDQ was 10.3 (SD = 7.3, range = 0–27). A one-sample t-test indicated that this mean was significantly higher than the mean for American children (t = 3.64, p = .001) in the normative sample (Centers for Disease Control, 2001). Notably, 25.4% of siblings scored above the recommended clinical cutoff of 17 on this scale. Second, the mean score of mothers on the CES-D was 17.8 (SD = 12.7, range = 0–55), which was significantly higher than the mean of 9.25 reported in the initial normative sample (t = 5.63, p < .001) and 52.1% of mothers (as compared to 19% of participants in the normative sample) scored at or above the clinical cutoff of 16 (Radloff, 1977). Finally, the mean T-score of typically developing siblings on the SRS was 51.51 (SD = 15.8). This mean was not significantly different from the mean T-score of 50 in the normative sample (t = .80, p > .10). 3.2. Path analysis The results of the path analysis are shown in Fig. 1 (see Table 2 for zero-order correlations). All correlations not predicted by our theoretical model were tested in the path model and found to be nonsignificant. They were subsequently trimmed from the model. It can be seen that child symptom severity was a positive predictor of maternal depressive symptoms (.58), which in turn was a positive predictor of sibling adjustment problems (.23). Child symptom severity was also a positive predictor of the child with ASD’s impact on siblings (.47), but sibling impact did not significantly predict sibling adjustment
[()TD$FIG]
Sibling Broader Ausm Phenotype Maternal Depression .23
.58 Child with ASD Ausm Severity
.02
.47
.50
Sibling Adjustment Problems .18
Child with ASD Impact on Siblings Solid Line: Significant path Dashed Line: Non-significant path Fig. 1. Path analysis testing for direct and indirect effects of Autism Spectrum Disorder (ASD) severity in the child with autism on adjustment problems in the typical sibling. Non-predicted correlations (based on the theoretical model) were found to be nonsignificant and were trimmed from the final model. Cross refer Table 2 for zero-order correlations between all study variables.
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Table 2 Correlation matrix. Autism severity Autism severity Sibling BAP Maternal depression Impact on siblings Sibling adjustment problems
(.88)
Sibling BAP .08 (.97)
Maternal depression **
Impact on siblings **
.27* .56** .38** .37** (.87)
.47 .22 .34** (.77)
.58 .17 (.94)
Sibling adjustment problems
Note: Cronbach’s alphas for each variable are depicted in parentheses along the diagonal. * p < .05. ** p < .01.
problems. As shown in Table 3, approximately 91% of the relationship between child autism severity and sibling adjustment was mediated through maternal depression and impact on siblings. That is, the total indirect effect of child autism severity on sibling adjustment involving these two mediators (the sum of the indirect effects) was 91% of the total effect of child autism severity (the sum of the direct and indirect effects) on sibling adjustment (i.e., .21/.23 100 = 91%). Furthermore, maternal depression was the more important of the two mediators, as it accounted for approximately 57% of the relationship between child autism severity and sibling adjustment (i.e., .13/.23 100 = 57%), compared to 35% for impact on siblings (i.e., .08/ .23 100 = 35%). Finally, the BAP in siblings was a direct positive predictor of adjustment difficulties (.50). Relationships between all other variables were nonsignificant. Overall, this model accounted for 37.3% of the variance in sibling adjustment. 3.3. Moderator analyses We performed regression analyses to test for statistical interactions between pairs of predictor variables in the model shown in Fig. 1 (cf. Cohen, Cohen, West, & Aiken, 2003). In each analysis, we entered the two predictor variables (meancentered) in the first step, and an interaction term in the second step (i.e., the product of the predictors). Our specific questions were; (1) does child autism severity interact with maternal depression or impact on sibling to predict sibling adjustment; (2) does sibling BAP interact with maternal depression or impact on sibling to predict sibling adjustment; (3) do child autism severity and sibling BAP interact with one another to predict sibling adjustment? Results are shown in Table 4. As can be seen, there was a significant interaction between sibling BAP and child autism severity on sibling adjustment, R2 = .45, b = .29, F = 9.3, p < .01. As can be seen in Fig. 2, there was a stronger positive
Table 3 Summary of direct and indirect effects of child symptom severity, maternal depression, and impact on siblings on sibling adjustment. Sibling adjustment (SDQ) Child symptom severity (ABC) direct effect !Indirect effect: parent depression (CES-D) !Indirect effect: impact on siblings (FIQ) Total effect Percent indirect effect (total) !Percent indirect effect: parent depression !Percent indirect effect: impact on siblings
.02 .13* .08 .23 91% 57% 35%
(.58 .23 = .13) (.47 .18 = .08) (.21/.23 = 91%) (.13/.23 = 57%) (.08/.23 = 35%)
Note: Coefficients for predictor ! mediator path and mediator ! outcome path were multiplied to obtain value for indirect effect, and direct and indirect effects were summed to obtain value for total effect (an indirect effect is assumed to be statistically significant if both of these effects are significant; cf. Kline, 2005). Strengths and Difficulties Questionnaire (SDQ); Autism Behavior Checklist (ABC); Center for Epidemiological Studies-Depression Scales (CESD); Family Impact Questionnaire (FIQ). * p < .05.
Table 4 Results of tests for statistical interactions in regression analyses.
Autism severity impact on sibling Autism severity maternal depression Sibling BAP impact on sibling Sibling BAP maternal depression Autism severity sibling BAP *
p < .01.
Inc. R2
F1,66
b
.17 .16 .40 .42 .45
1.87 1.21 2.57 2.74 9.28*
.16 .14 .16 .17 .29
[()TD$FIG]
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25
Sibling Adjustment Difficules
High Ausm Severity Low Ausm Severity 20
15
10
5
0 Low
High
Sibling Broader Ausm Phenotype Fig. 2. Predicted values for sibling adjustment (Strengths and Difficulties Questionnaire) for low vs. high levels of autism severity in the child with autism (Autism Behavior Checklist) and broader autism phenotype in the sibling (Social Responsiveness Scale).
relationship between BAP in the sibling and sibling adjustment at high levels of ASD severity than at lower levels. No other interactions were significant (Fs < 3). 4. Discussion Siblings of children with ASD exhibited higher rates of adjustment problems than children in the normative sample. This finding is consistent with reports suggesting that siblings of children with ASD may be at an increased risk of adjustment problems. Similarly, mothers of children with ASD reported significantly higher rates of depressive symptoms than the normative sample. Again, this finding is consistent with research indicating an increased risk of depression in mothers of children with ASD. Our findings suggest two possible mechanisms by which siblings of children with ASD may be at heightened risk for adjustment difficulties. First, siblings of children with more severe ASD symptoms were more likely to exhibit adjustment difficulties. This finding is consistent with other studies that have found relationships between autism severity and behavior problems of children with ASD and adjustment difficulties in their typically developing siblings (Benson & Karlof, 2008; Hastings, 2003b, 2007). However, we found that this relationship was fully mediated by maternal depressive symptoms. Thus, our results do not support the idea that child autism severity affects sibling adjustment directly. Rather, the relationship is likely influenced by increased rates of depressive symptoms in mothers of more severely affected children with ASD, a finding which is consistent with research indicating detrimental effects of maternal depression on children (Downey & Coyne, 1990). A parent who is experiencing significant levels of depressive symptoms (potentially as a result of parenting a child with severe ASD symptoms) may be less effective in balancing the demands of multiple children with different developmental needs and may be less adept at providing both necessary emotional support and effective discipline. In addition, a depressed parent may model less adaptive coping styles that are then adopted by their typically developing children. Interestingly, although the impact of the child with ASD on the sibling was associated both with child autism severity and with sibling adjustment, it did not mediate the relationship between these two variables in the path analysis. This may be partially explained by the observed positive correlation between sibling impact and maternal depression (a correlation between the two mediator variables in the path model reduces the variance explained by each independent predictor). It is possible that mothers who are experiencing more depressive symptoms allow the child with ASD to have a greater impact of the sibling’s life. For example, depressed mothers may have less energy to attend to the sibling’s social/emotional needs or may monitor the child with ASD less closely, leading to negative behaviors such as aggression toward the sibling. Second, siblings of children with ASD who exhibit a greater number of BAP characteristics may be more likely to have adjustment difficulties. Further, this relationship appears to be moderated by autism severity in the child with autism. While the siblings in this sample did not score above average on our measure of BAP as a group, approximately 23% of siblings scored in the at-risk or clinical range for an ASD diagnosis, suggesting that many of the siblings in our sample were experiencing a significant number of characteristics of autism. Siblings who exhibit characteristics associated with the BAP, such as social difficulties and maladaptive personality traits, may be less likely to seek social support when needed and more likely to react negatively to the stress of having a sibling with ASD or other stressful life events. Having a sibling with more severe ASD characteristics and general behavior problems (the Autism Behavior Checklist measures both symptoms specific to autism and general behavioral problems such as tantrums and aggression) may serve as one such stressor for siblings of children with ASD. While siblings who themselves exhibit few ASD traits may be able to relate to and empathize with a
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sibling at any functioning level, relating to a lower-functioning sibling may be more difficult for siblings who have difficulties with important skills such as social relatedness, empathy, and emotional awareness. This finding is consistent with previous research indicating that siblings with more BAP characteristics are more likely to develop depression and anxiety in response to stressful life events (Orsmond & Seltzer, 2009). To our knowledge, this is the first study to find a direct relationship between the BAP and adjustment difficulties in siblings of children with ASD. This study has several limitations. First, although evidence suggests that internet parent report of ASD status is valid (Rosenberg et al., 2009), we were unable to confirm the ASD diagnoses in the ASD sample or rule out an ASD diagnosis in the typically developing siblings. While we have only one measure of ASD symptoms in the sibling with autism (the ABC), the mean ABC score in the children with autism in this sample was 59.2 (SD = 27.8). This score falls well above the cutoff score for autism that Wadden, Bryson, and Roger (1991) reported to best discriminated autism from non-autism groups on the ABC. In addition, the Interactive Autism Network (IAN), from which the families in this study were recruited, asks parents to fill out a variety of diagnostic questionnaires for the children with ASD. While we do not have access to the scores of specific children in our sample on these measures, Lee, Marvin, Watson, Piggot, and Law (2010) found that 98% of a group of children representative of the overall pool of participants in the IAN network were ASD-positive based on clinician’s best estimate, with 99% scoring ASD-positive based on the Autism Diagnostic Interview-Revised and 93% scoring ASD-positive based on direct observational assessment. These data indicate that the great majority of children involved in the IAN subject pool do have ASD diagnoses. Finally, it is important to note that while the diagnoses of the children in this study were not confirmed by investigators (and thus it is possible that the sample includes some children who do not meet full criteria for ASD), the families in this study are self-identifying as having a child with ASD. Families of children with ASD who are accessing the family-related services in the community where these findings are likely to be most applicable (e.g., parent or sibling support groups) are those who self-identify as having a child with ASD. Therefore, including these families in this type of research may increase the ecological validity of the findings. However, future research that can replicate these findings in a group of families whose diagnoses are confirmed by the investigators is an important next step. Second, because all data were collected from the children’s mothers, it is possible that the relationships between the different measures in this study were influenced by overall positive or negative reporting biases of individual mothers. In particular, high levels of maternal depression might lead to a negative reporting bias on measures of child functioning for both children (Fergusson, Lynskey, & Horwood, 1993). However, Davis and Carter (2008) found that parental depression may affect parental appraisal of child behavior less in families of children with ASD than families of typically developing children. Nevertheless, it is important for future research to obtain data from multiple informants, including the typically developing siblings, to ensure that the relationships found in this study were not primarily due to response bias of a single reporter. Third, our sample consisted primarily of families from Caucasian, highly educated, married, and middle- to high-income households. Therefore, the findings of this study cannot be generalized to all families with a child with ASD. Finally, as the data in this study were cross-sectional, the direction of effect of the associations cannot be determined. Thus, future research that uses longitudinal designs with families with a wider range of racial, ethnic, and socioeconomic backgrounds is needed. These findings have important implications for the assessment and treatment of family members of individuals with ASD and stress the need for a family-level approach to treating difficulties in these families. First, given the high rates of maternal depression and sibling adjustment difficulties found in this study, particularly among family members of severely affected individuals with ASD, it is important for those who treat people with ASD (e.g., teachers, psychologists, physicians) to be alert for potential difficulties in other family members in order to provide needed support or make appropriate referrals. These findings also stress that characteristics of the sibling with autism, the typically developing sibling, and the mother may all interact to contribute to adjustment difficulties in typically developing siblings. Thus, treatments or support groups that include the entire family may be more effective for these siblings than individual treatments that do not address the characteristics and needs of the entire family. In sum, our findings suggest that adjustment problems in siblings of children with ASD are related both to increased symptom severity in the child with ASD, via its effect on maternal depressive symptoms, and the expression of a greater number of characteristics of autism in the siblings themselves. Further, greater expression of autism characteristics in the siblings was most detrimental to sibling adjustment when the child with ASD had more severe symptoms. Future research should examine whether these relationships persist when input on child and sibling behavior is solicited from multiple sources and from a more diverse sample. Acknowledgements This research was supported by grants from Autism Speaks to the first and second authors. We would like to thank the families who participated in the research. References Bailey, A., Palferman, S., Heavey, L., & LeCouteur, A. (1998). Autism: The phenotype in relatives. Journal of Autism and Developmental Disorders, 28, 369–392. Baker-Ericzen, M. J., Brookman-Frazee, L., & Stahmer, A. (2005). Stress levels and adaptability in parents of toddlers with and without autism spectrum disorders. Research and Practice for Persons with Severe Disabilities, 30, 194–204. Bauminger, N., & Yirmiya, N. (2001). The functioning and well-being of siblings of children with autism: Behavioral-genetic and familial contributions. In J. A. Burack, T. Charman, N. Yirmiya, & P. R. Zelazo (Eds.), The development of autism: Perspectives from theory and research (pp. 61–80). Mahwah, NJ: Lawrence Erlbaum Associates.
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