Richard P. Hastings 1 INTRODUCTION

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1 Journal of Autism and Developmental Disorders, Vol. 33, No. 2, April 2003 ( 2003) Behavioral Adjustment of Siblings of Children with Autism Engaged in Applied Behavior Analysis Early Intervention Programs: The Moderating Role of Social Support Richard P. Hastings 1 There have been few studies of the impact of intensive home-based early applied behavior analysis (ABA) intervention for children with autism on family functioning. In the present study, behavioral adjustment was explored in 78 siblings of children with autism on ABA programs. First, mothers ratings of sibling adjustment were compared to a normative sample. There were no reported increases in behavioral adjustment problems in the present sample. Second, regression analyses revealed that social support functioned as a moderator of the impact of autism severity on sibling adjustment rather than a mediator or compensatory variable. In particular, siblings in families with a less severely autistic child had fewer adjustment problems when more formal social support was also available to the family. The implications of these data for future research and for practice are discussed. KEY WORDS: Applied behavior analysis; autism; siblings; social support. INTRODUCTION Over the past two decades, a number of researchers have reported encouraging data on the efficacy of intensive early intervention approaches for children with autism. Intervention models with the strongest empirical base have been associated with the principles of applied behavior analysis (ABA) (Smith, 1999). One of the most influential of these behavioral early intervention models has undoubtedly been that of Lovaas et al. (e.g., McEachin, Smith, & Lovaas, 1993; Lovaas, 1987). There has been considerable academic debate associated with the UCLA project (e.g., Gresham & McMillan, 1997; Kazdin, 1993; Lovaas, Smith, & McEachin, 1989; Mesibov, 1993; Schopler, Short, & Mesibov, 1989; Smith & Lovaas, 1997), and parents of children with autism have been instrumental in disseminating ABA intervention within the United States (e.g., Jacobson, 2000) 1 School of Psychology, University of Wales, Bangor, Gwynedd, LL57 2DG, Wales, United Kingdom, r.hastings@bangor. ac.uk 141 and internationally (e.g., Hastings & Johnson, 2001; Mudford, Martin, Eikeseth, & Bibby, 2001). Researchers assessing the efficacy of ABA intensive early intervention for children with autism have understandably focused on outcomes for children with autism. There are currently few studies presenting data on the impact of engagement in intensive ABA interventions upon family functioning. Such data are likely to be significant clinically for several reasons. First, family members of children with autism may already be at increased risk of stress and other psychological problems, including depression (e.g., Gold, 1993; Koegel et al., 1992). Clinicians need to be aware of any additional negative effects of engagement in ABA interventions on the family in order to offer appropriate support. Furthermore, research on factors contributing to stress and other psychological problems in these families is needed. Second, many parents are involved as therapists on their child s program. Their performance is likely to be affected by their levels of stress. Although there are currently no data addressing the potential impact of stress levels on therapist performance in ABA /03/ / Plenum Publishing Corporation

2 142 Hastings programs, this seems a reasonable assumption. Thus, psychological distress may also have a direct impact on the quality of ABA intervention. A small number of published studies have provided data on the functioning of family members in the context of ABA intervention. Several researchers have reported parental stress outcomes as a part of the evaluation of an ABA intervention. For example, Birnbrauer and Leach (1993) found that mothers in an ABA treatment group (n 9) reported less stress than control group mothers (n 5) after 2 years of the intervention program, although they were similar at intake. Smith et al., have also reported on parental outcomes (Smith, Buch, & Gamby, 2000a; Smith, Groen, & Wynn, 2000b). Two approaches have been adopted. First, as in Birnbrauer and Leach s (1993) study, the Parenting Stress Index (Abidin, 1990) was used with six mothers of children on parent-directed programs at 3 months into therapy and at a 2 3 year follow-up (Smith et al., 2000a). Although the sample size was too small for formal statistical analysis, mothers stress levels had decreased on average from the 80th to 90th centiles down to the 25th to 35th centiles. Smith s second approach has been to seek parental ratings of stress during treatment at follow-up points (i.e., parents report retrospectively on stress during treatment). In comparing parents who had engaged in ABA intensive treatment for their child with autism (n 15) with a comparison group undergoing a parent-training intervention (n 13), Smith et al. (2000b) found no differences in terms of ratings of stress for the child or the parents during therapy. Although the result was reported as nonsignificant, the data presented by Smith, et al. (2000b) do show an effect size for the difference between intensive and parent-training groups on parent stress during treatment of over 1.0 (present author s calculation). Parents in the intensive intervention group reported less stress on themselves during treatment than parents in the less intensive parenttraining group. In a larger sample, such a difference would be likely to be statistically significant. In a further recent cross-sectional study of 141 parents whose children with autism were engaged in various stages of ABA intervention, Hastings and Johnson (2001) reported that mothers in the sample (n 130) reported similar levels of stress to mothers of children with autism in other research studies. Hastings and Johnson (2001) also explored predictors of stress within the sample of parents. Program variables (e.g., child s age when the program was started, length of time the child had been engaged on the program, whether parents were also therapists for the child) did not predict parental stress, but other psychological variables did so (e.g., social support, positive reframing coping strategies, and parents beliefs about the efficacy of the ABA methods). The research reviewed above indicates that parents whose children with autism are engaged in intensive ABA interventions may be no more stressed than other parents of children with autism, and that stress may decrease over the course of an ABA intervention. There are still many unanswered questions about the impact of intensive ABA interventions on parents, but perhaps the most stark point to date is the absence of data on other family members, particularly siblings. If a great deal of the family s financial and time resource is being directed into the ABA program for the child with autism (Johnson & Hastings, 2002), then siblings may well be at an increased risk of negative effects. The purpose of the present paper is to explore the potential impact of intensive ABA programs on the psychological adjustment of siblings. In particular, the analysis addresses factors that may predict sibling adjustment. However, data are also presented on how sibling functioning in ABA families compares to normative samples. A focus on siblings of children on intensive ABA programs is warranted for a number of reasons. First, it is important clinically to be aware of family outcomes within such programs given the reality that many families are engaged in them internationally. Second, the intensive nature of ABA home programs logically has implications for quantitative and perhaps qualitative dimensions of parent-child relationships, which may then affect sibling adjustment. Third, ABA programs are perhaps unique in the frequency of input to the family home from therapists and their supervisors. There is likely to be some variability in the perception of support provided by the therapy team to the family. In particular, where parents have relatively poor relationships with their child s therapy team, this is likely to reduce the level of support, which again may affect parents relationships with siblings of the children with autism. In terms of broader research on the potential impact of children with disabilities on their siblings, narrative reviews have tended to conclude that there is some evidence of negative effects but also evidence of positive effects (e.g., Boyce & Barnett, 1993; Hannah & Midlarsky, 1999; Howlin, 1988; Summers, White, & Summers, 1994). A recent quantitative review pooling data from 25 studies suggested that there is a small negative effect of a child with mental retardation on his or her siblings (Rossiter & Sharpe, 2001). Research on siblings of children with autism supports this finding in that, compared to control groups, such children

3 Social Support and Sibling Adjustment 143 appear to present with more psychological problems (Bägenholm & Gillberg, 1991; Fisman et al., 1996; Fisman, Wolf, Ellison, & Freeman, 2000; Gold, 1993; Rodrigue, Geffken, & Morgan, 1993; Roeyers & Mycke, 1995). In addition to considerable interest in the question of whether siblings of children with disabilities have more or fewer psychological problems than other children, factors that increase or decrease such effects have been explored. In particular, several demographic and static family variables have been suggested as mediators of the impact of children with disabilities on their siblings including: sibling sex, match between the sex of the two children, whether the sibling is younger or older than the child with a disability, the age of the sibling, and whether the child with disability resides in the home or is placed outside of the family. In general, these variables have been found not to have very strong effects on sibling adjustment in families of children with autism or other developmental disabilities (Eisenberg, Baker, & Blacher, 1998; Gold, 1993; Hannah & Midlarsky, 1999; Mates, 1990; McHale, Sloan, & Simeonsson, 1986; Roeyers & Mycke, 1995). Less attention has been given to the role of psychological factors, such as coping strategies and social support, identified in stress and coping theories as applied to families of children with disabilities (e.g., Beresford, 1994; McCubbin & Patterson, 1983). However, a number of studies have suggested that the social support available to families may well affect sibling adjustment. First, some research has shown that variables conceptually related to social support, such as parental satisfaction with the marital relationship and the quality of family life, are associated with sibling adjustment (e.g., Hannah & Midlarsky, 1999; Rodrigue et al., 1993). Second, siblings own perception of social support available to them has been found to predict parents and teachers ratings of their adjustment (Wolf, Fisman, Ellison, & Freeman, 1998). Finally, social support as perceived by parents has been found to be associated with sibling adjustment in families of children with developmental and other disabilities (e.g., Benson, Gross, & Kellum, 1999; Dyson, Edgar, & Crnic, 1989). In existing research, social support has typically been explored in terms of its main effect relationship to sibling adjustment. The implication here is that social support may act in one of two ways. First, social support may mediate (cf., Baron & Kenny, 1986) the relationship between child disability and sibling adjustment (i.e., having a sibling with a disability reduces access to social support from others, which affects sibling adjustment). Second, social support could be described as a compensatory factor (cf., Luthar & Zigler, 1991). Thus, within a sample of siblings of children with disabilities, those children in families with higher levels of social support may have less negative and/or more positive adjustment. There is a third possibility in which social support might act as a protective factor (cf., Rutter, 1985). In this case, under conditions of increased risk (e.g., child with more severe disabilities, more care demands, or more problem behavior), those siblings in families with higher levels of social support will have fewer adjustment problems than those siblings in families with lower levels of social support. However, at low levels of risk (e.g., child with less severe disabilities, fewer care demands, or less problem behavior), social support would have no effect on sibling adjustment. This effect is similar to the concept of a moderator variable (Baron & Kenny, 1986) where there is an interaction between one variable and another to affect an outcome. In the present study, I focus on the role of social support available to the family and how it may affect sibling adjustment. The three models described above are explored. A supplementary aim is to present preliminary data on the adjustment of siblings of children with autism engaged in intensive ABA early intervention programs. Although no control group was recruited for the present research, ratings of sibling adjustment are compared to normative data. METHOD Participants Participants were drawn from a larger survey of parents of children with autism engaged in intensive ABA early intervention programs in the United Kingdom (Hastings & Johnson, 2001). One hundred and forty-one parents participated in the research. For the present study, data are presented on a subsample that was able to provide data on siblings of their young child with autism. Because of the small number of fathers responding to the survey (11 from 141), only mothers were included in the present analysis. Of the 130 mothers from the full sample, 19 had no other children, 27 had no other children within the age range appropriate for the measure of sibling adjustment (4 16 years), and 6 failed to complete the measure of sibling adjustment despite having a child of appropriate age. Thus the present study focuses on mothers and siblings of 78 young children with autism. Mothers were asked to report on

4 144 Hastings one sibling only: the child closest in age to the child with autism whose age was in the range 4 16 years. In all cases, the mothers were the biological parents of the child with autism and in all but two cases they were the biological parents of the sibling. The age of these respondents ranged from 26 to 51 years, with a mean of (SD 4.34) years. Seventy four (94.9%) of the mothers were married and living with their spouse, two were living with a partner, and two were divorced, separated, or single and not living with a partner. Almost every mother (97.5%) reported that they were currently in a general state of good health. The siblings were on average 6.70 years of age (SD 2.36). Thirty-five were the full biological brothers, and 41 were the full biological sisters of the child with autism. Two mothers reported on half-sisters of their child with autism. Thirty-four siblings were of the same gender as the child with autism, whilst the majority were older than their brother or sister with autism (n 70, compared with eight who were younger). Further demographic details of the mothers, their young child with autism, their family, and the family s involvement in the ABA intervention program can be found in Table I. In every respect bar one, the present sample were representative of the full sample reported by Hastings and Johnson (2001). Of course, families in the present subsample did contain more siblings on average than the full sample. Table I. Further Demographic Characteristics of the Sample Characteristic Percentage of sample/mean (SD) Mother has bachelor, master, 46.1% or doctoral degree Mother in full- or part-time employment 100% Mother s partner in employment 96.2% Sex of child with autism Male 88.5% Female 11.5% Age of child with autism (years) 5.04 (1.61) Child with autism lives with mother 98.7% Respite care available to family 17.9% Respite care regularly used by family 6.4% Number of other siblings in family 1.53 (.72) Mother acting as therapist on child s program 69.2% Mother s hours per week working on program* 6.88 (3.45) Mother s partner acting as therapist on 23.1% child s program Partner s hours per week working on program* 3.94 (1.76) Length of time on program (months) (10.83) Age of child when program started (months) (17.88) * Mean hours calculated for those acting as therapists on their child s program only, not across whole sample. Materials In addition to a questionnaire designed to elicit the demographic information summarized above, three measures were included in the present analysis. Autism Behavior Checklist The Autism Behavior Checklist (ABC) (Krug, Arick, & Almond, 1980) was used to generate an overall index of the level of autism symptomatology ( severity of autism) in the child with autism. The validity of the ABC has been questioned on several occasions (e.g., Sevin, Matson, Coe, Fee, & Sevin, 1991; Wadden, Bryson, & Rodger, 1991). However, in the present study it was used simply as an index of autism symptomatology and not as a diagnostic instrument. The checklist was presented to parents in the simple Yes/No format (Volkmar et al., 1988) and the total score only, calculated using the weightings suggested by Krug et al. (1980), was used in the analyses reported below. Family Support Scale (FSS) Dunst, Jenkins, and Trivette s (1984) 18-item FSS was used to measure social support for the family. Two scores were derived from this measure. These were: (1) a weighted score for the helpfulness of informal sources (spouse, family, friends, other informal supports) of support available to the family, and (2) a weighted score for the helpfulness of support from professionals and services available to the family, including the support associated with the early intervention program. These two measures are from McConachie and Waring s (1997) revised scoring procedures for the FSS. They represent the mean helpfulness ratings for the support sources available to the family. These two scores from the FSS have a number of advantages. First, they take into account that families will each have a different range of support sources available to them and consider mothers ratings independent of this factor. Previous research has found that the perceived helpfulness of social support sources is more salient to parents than the mere availability of support sources (e.g., Frey, Fewell, & Vadasy, 1989). Second, these scores represent a distinction between professional input and informal supports. A weighted score for overall helpfulness for all support sources is likely to mask this important distinction. In the present study, scores for formal and informal support sources were moderately correlated (r.53), whereas associations between

5 Social Support and Sibling Adjustment 145 these scores and a weighted score across all support sources were high (both correlations.85). Sibling Behavioral Adjustment Mothers were asked to complete the Strengths and Difficulties Questionnaire (SDQ) (Goodman, 1997) as a measure of sibling behavioral adjustment. This questionnaire was developed from the Rutter scales (Rutter, Tizard, & Whitman, 1970) and includes 20 problem items across four domains (emotional problems, conduct problems, hyperactivity, and peer problems). The SDQ also includes a five-item prosocial behavior scale. Each of the 25 items is rated on a three-point scale from 0 (not true of the child), through 1 (somewhat true of the child), to two (certainly true of the child). Despite being a comparatively short instrument for the assessment of children s psychological adjustment, the SDQ has been shown to be highly correlated with other well-established measures (Goodman & Scott, 1999). Dimensional scores from the SDQ were used. These are obtained by summing the scores on items within each of the five domains (a total score is also derived by summing the scores on the four problem domains). Procedure The main survey sample (see Hastings & Johnson, 2001) was recruited through the U.K. support organization for parents of children with autism engaged in ABA programs. Four hundred and fifty questionnaires were mailed out through the support group to their parent members. Questionnaires were returned anonymously to the research team. One hundred and forty-one members replied, constituting a response rate of 31%. This response rate is at the low end of the typical range for a postal survey of this sort. However, there were two systematic factors in particular that acted to reduce the response rate. First, the support group included parent members who do not have a child with autism but have other disabilities. The questionnaire explicitly asked about children with autism, and these other parents would have been unlikely to respond. There are no data relating to how many families would have been in this position. Second, not all members of the organization were parents of a child currently engaged in an early intervention program. The support group s data at the time of the study suggested that 250 families were conducting intensive ABA early intervention programs in the United Kingdom. If we assume that this figure is reasonably accurate, the true response rate for the study is closer to 60%. There are no data available about nonresponding families because the survey was returned anonymously. RESULTS Sibling Behavioral Adjustment Compared with Normative Data Mothers ratings of sibling behavioral adjustment were compared with normative data for the SDQ from 10,298 children tested as a part of a large-scale study of mental health in British children (Meltzer, Gatward, Goodman, & Ford, 2000). One-sample t tests were used to compare mean scores from the present sample with those from the normative sample. These mean scores for the present sample on all of the SDQ domains and the results of the statistical tests are summarized in Table II. The results show that the present sample of siblings of children with autism differs significantly from normative data on three of the SDQ problem domains and the total behavior problems score. In each case, the present sample is reported as having fewer problems. Family Social Support and Sibling Behavioral Adjustment The main analyses focused on two dimensions of sibling behavioral adjustment: behavior problems (SDQ total problems score), and prosocial behavior (SDQ prosocial behavior domain score). Before conducting the main regression analyses, exploratory analyses were conducted on variables that may be related to sibling behavioral adjustment. The effects of demographic and sibling variables suggested in previous research to be related to sibling outcomes (sex of child with autism, sex of sibling, whether or not the children were of the same gender, and age of the sibling), and also salient ABA program variables (whether or not the mother or father were acting as a therapist on the program, and the length of time that the child with autism had been engaged in the program), were explored. These analyses revealed only two effects. First, older siblings were reported as having more prosocial behavior [r(78).26 p.05]. Second, children whose fathers acted as a therapist on the ABA program were rated as having fewer prosocial behaviors than those children whose fathers did not have this role [t(76) 2.22, p.05]. These two variables were therefore included in the analysis of sibling prosocial behavior.

6 146 Hastings Table II. SDQ Scores for Siblings of Children with Autism Compared to Normative Data Present sample (n 78) Normative sample (n 10,298) SDQ score M SD M SD t value Effect size Emotional problems Conduct problems **.36 Hyperactivity *.30 Peer problems **.33 Prosocial behavior Total score **.33 *p.01, **p.001. The three competing models of the effect of family social support on the relationship between the severity of autism of the child engaged in the ABA program and their sibling s behavioral adjustment were explored in hierarchical regression analyses. In the first step, demographic variables associated with sibling adjustment (for the analysis of prosocial behavior only) were entered. In the second step (first step for SDQ total score), the total ABC score (severity of child s autism) was entered. In the third step (second for SDQ total score), the two FSS scores were entered (mean helpfulness of informal and formal social support sources). Finally, two interaction terms were entered derived from the product of the z transformed ABC and FSS scores. These transformations are used to center the data and eliminate the problems of deriving product terms from variables measured on scales with different ranges. Following Baron and Kenny (1986), social support would have been found to mediate the impact of autism on sibling adjustment if autism severity was a significant predictor when first entered into the regression equation but became nonsignificant once social support scores were entered. Furthermore, if the interaction terms in the final blocks of the analyses were found to be significant (i.e., after controlling for the main effects of their constituent variables), this would be taken as evidence of a moderated relationship. Finally, if the social support variables were significant predictors of sibling adjustment when first entered into the regression equation it could be concluded that they function as compensatory factors. The results of these regression analyses are displayed in Table III. For the analysis of sibling prosocial behavior, there is no evidence that family social support mediates the relationship between autism severity and sibling adjustment. In fact, the ABC score is only a marginally significant predictor of prosocial behavior at best. There is also no evidence that social support is a compensatory factor in this context. Finally, there is no support for social support as a moderator variable. For the analysis of sibling problem behavior, again there is no evidence of mediation (in fact, the ABC Table III. Regression Analysis of Sibling Behavioral Adjustment SDQ prosocial behavior SDQ total problems Step/Predictor p R 2 F change p R 2 F change Step * Sibling age Father as therapist Step ** ABC total score Step Informal social support Formal social support Step ABC informal support ABC formal support *p.01, ** p.001.

7 Social Support and Sibling Adjustment 147 score remained a significant independent predictor of sibling adjustment at the second step of the analysis) nor compensatory effects. However, the interaction between the ABC score and formal social support does make a significant independent contribution to the prediction of sibling adjustment, suggesting a moderated effect. This step of the analysis does not lead to a significant increase in the proportion of variance in SDQ scores accounted for. However, several authors (e.g., McClelland & Judd, 1993) have described the difficulties in identifying significant interaction terms in moderated multiple regression analyses. In particular, applied research suffers from the fact that the full range of scores on a variable is used in contrast to experimental research where samples can be selected for their extreme positions on a distribution. McClelland and Judd (1993) state that it is not untypical for salient interaction effects in applied research to account for only 1 3% of the overall variance in a regression analysis. Given that the two interaction terms together account for 5% of the variance in the present analysis, and that the regression coefficient for the formal support interaction term is significant at p.05, this effect is worthy of further exploration. To explore the nature of the interaction between formal social support and the ABC total score for the analysis of the SDQ total problems score, a data plot was derived based on the guidelines developed by Aiken and West (1991). Figure 1 shows predicted values (i.e., derived from regression equations) for the SDQ total problems score at low (1 SD below the mean) and high (1 SD above the mean) ABC scores for each of three levels of the formal social support score (1 SD below the mean, at the mean value, and 1 SD above the mean). Figure 1 demonstrates that at low levels of ABC scores, siblings whose families have lower levels of formal social support are rated as having more behavioral adjustment problems. At high ABC scores, family formal social support does not appear to affect sibling adjustment. DISCUSSION The results of the comparison of the present sample of siblings of young children with autism engaged in intensive ABA early intervention programs with normative data for the SDQ provide no evidence for a negative effect on sibling adjustment. These results concur with existing published data also suggesting no negative effect of involvement in intensive ABA intervention on parental functioning (Birnbrauer & Leach, 1993; Hastings & Johnson, 2001; Smith et al., 2000a, 2000b). However, it would not be appropriate to conclude that siblings in these circumstances are better adjusted than other children in the United Kingdom for several reasons discussed below. Fig. 1. Interpretation of the moderating effect of family formal social support on the relationship between autism severity and sibling problem behavior.

8 148 Hastings First, the differences found are relatively small (see Effect Sizes in Table II). Second, it is clear (see Table 1) that the present sample is highly socially advantaged (Hastings & Johnson, 2001). Thus the present sample of siblings is unlikely to represent the range of social advantage and disadvantage in the normative sample from Meltzer et al. (2000). Socioeconomic disadvantage may well moderate the impact of intensive ABA programs on the adjustment of siblings of children with autism. That is, where financial resources in particular are high, siblings may be less affected than when families are struggling financially. Such a hypothesis should be addressed explicitly in future research. A third issue is that the mothers of the children rather than an independent rater reported on siblings behavior problems. In addition to the source variance problem inherent in such a measurement approach, there are likely to be a number of systematic biases in operation. For example, families engaged in with intensive ABA interventions may well wish to minimize reports of any negative effects on family members because of significant demands on financial and other resources (cf., cognitive dissonance). Furthermore, mothers may have attributed any positive changes in their other children to the presence of the ABA program for the child with autism because, from their perspective, this has been the largest recent change in the family s experience. Finally, mothers may have been aware of the risk of adjustment difficulties in siblings of children with autism and been keen to represent their family in a positive light. Possibilities such as these are always difficult to evaluate in survey research but could be explored by focusing on data from siblings themselves (see below) or on qualitative research with parents. Further research is clearly needed to establish the impact of intensive ABA interventions on family members, including siblings. In particular, appropriate comparison groups are required. For example, a key test is for any differences between siblings in families engaged in intensive ABA interventions and siblings in similar families engaged in less intensive or no particular interventions for their children with autism. Comparisons with children whose siblings are engaged in other intensive interventions, such as Son-Rise (Kaufman, 1994), would also help to establish the relative effects of variables such as treatment intensity and changes in parents behavior management skills. Longitudinal research is also needed. Although there were no effects of the length of time that the ABA program had been in place on sibling adjustment in the present study, it is possible for example that siblings experience a period of upheaval within the first few months of an intensive ABA program. Such an effect could not be explored in the present sample given the small numbers of programs that had started within the previous few months. In terms of the potential impact of family social support on sibling adjustment within the sample, there was no support from the regression analyses that social support acted either as a mediator or as a compensatory factor. However, there was evidence that formal social support moderated the impact of the severity of symptoms of the child with autism on their siblings adjustment. Specifically, when children had less severe autism their siblings were less at risk for behavior problems when the family also received high levels of formal social support. This effect is likely to be mostly accounted for by the support that the family receives from their involvement in the ABA program. The mean rating for the helpfulness of the early intervention team as a source of support was significantly higher than the mean helpfulness rating for all formal sources of support together [t(69) 17.65, p.001], and 70% of mothers gave this single item the highest rating in terms of helpfulness to the family. This effect requires more research attention to elucidate the mechanism by which support from intensive ABA intervention may affect siblings. In particular, it is important to establish whether siblings perceive benefits or problems for the family and for themselves. The interaction between autism severity and formal social support does not appear to equate to a protective effect, as these are defined in terms of their action at high risk levels (Rutter, 1985). However, what needs to be remembered is that siblings of all children with autism may be at increased risk for adjustment problems. Therefore, those siblings in the present sample whose brother or sister had less severe symptoms of autism might be conceptualized as a high-risk group, whereas siblings of the more severely affected autistic children may be an extreme-risk group. Other researchers have suggested the implied curvilinear relationship here: that protective factors might take their effect but not in situations where the level of risk becomes too high (e.g., Garmezy, Masten, & Tellegen, 1984). This potential nonlinear relationship could be explored in future research perhaps via the inclusion of a genuine low-risk group (e.g., siblings of children with no disabilities, or perhaps a milder cognitive disability). Before considering the practical implications of the present results, it is important to point out further methodological issues that should be born in mind when interpreting the data. The most significant of these is the problem of source variance: mothers provided data

9 Social Support and Sibling Adjustment 149 on their child with autism, the support available to the family, and the adjustment of the siblings. Ideally, the present results should be replicated with independent and multiple ratings of autism severity and also sibling adjustment. Multiple perspectives would also include self-ratings of the siblings and a broader focus on siblings experiences. Siblings may not perceive an impact on their own adjustment, but they may well report other outcomes of intensive ABA programs such as changes in attitudes toward their sibling or their knowledge about autism, differential treatment by their parents, and the overall impact on the family s social life. A second issue relates to definition of sibling adjustment, to identify effects upon siblings. In the present research, a measure addressing positive and negative aspects of behavioral adjustment was employed. However, other domains of adjustment may be important to measure, including sibling self-perception (e.g., Mates, 1990) and the sibling relationship itself (e.g., Wolf et al., 1998). Finally, as indicated earlier, the ABC may not be a good measure of autism. Thus the effects of social support found in the present analysis may be limited by psychometric limitations of this measure. Future research studies should include a broader assessment of the severity of the disabilities of the child with autism, such as adaptive behavior skills and general behavior problems. One or both of these factors might underlay the impact of autism on siblings. Turning to the practical implications of the present findings, at present there are no data to alert clinicians to family functioning problems in the context of intensive ABA early intervention for children with autism. However, this may well be because families of relatively high socioeconomic status have been studied in research to date. Such families may well have the financial and psychological resources to support such an intensive intervention model. As ABA intensive intervention becomes more widely available, issues relating to family functioning may become more pertinent. A further practical implication may be that key characteristics of the support provided by early intervention therapy teams may be advantageous for a broad range of families of children with developmental disabilities. For example, regular contact with motivated therapists, often volunteer university students, might prove an effective way of supporting families and developing children s skills even outside of the context of a 40-hours-per-week intensive one-to-one training model for the child. Future research should address the dimensions of support from early intervention therapists that may be most beneficial for families. REFERENCES Abidin, R. R. (1990). Parenting Stress Index. Odessa, FL: Psychological Assessment Resources. Aiken, L. 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