- Email: [email protected]
Quality of life as a mediator between behavioral challenges and autistic traits for adults with intellectual disabilities
Research in Autism Spectrum Disorders 7 (2013) 624–629
Contents lists available at SciVerse ScienceDirect
Research in Autism Spectrum Disorders Journal homepage: http://ees.elsevier.com/RASD/default.asp
Quality of life as a mediator between behavioral challenges and autistic traits for adults with intellectual disabilities Domingo Garcı´a-Villamisar a,1,*, John Dattilo b,2, Johnny L. Matson c,3 a
Complutense University of Madrid, Spain Penn State University, USA c Louisiana State University, USA b
A R T I C L E I N F O
A B S T R A C T
Article history: Received 26 November 2012 Accepted 29 December 2012
A multiple mediation model was proposed to integrate core concepts of challenging behaviors with autistic traits to increase understanding of their relationship to quality of life (QoL). It was hypothesized that QoL is a possible mediator between the severity of challenging behaviors and autistic traits in adults with intellectual disability. These constructs are of vital importance because they are essential variables for people with autism, and obviously they influence their psychosocial development. Participants were 70 adults with autism spectrum disorders (ASD) and moderate intellectual disabilities (ID). Results indicated that several dimensions of QoL mediated the relationships between autistic traits and challenging behaviors. The dimensions of QoL, Satisfaction, Competence/Productivity, and Autonomy/Independence are mediators between autistic traits and challenging behaviors. Implications of these data are discussed. ß 2013 Elsevier Ltd. All rights reserved.
Keywords: Autism spectrum disorders Intellectual disabilities Behavioral challenges Quality of life
1. Introduction Autism spectrum disorders (ASD) and intellectual disabilities (ID) often co-occur at high rates with the relationship between the two disorders being enigmatic (Matson & Shoemaker, 2009). With the increase in life expectancy in occidental societies, the concern for promoting a positive quality of life (QoL) for adults who have both ASD and ID is growing (Billstedt, Gillberg, & Gillberg, 2011; Cappe, Wolff, Bobet, & Adrien, 2011; Cottenceau et al., 2012; Garcia-Villamisar & Dattilo, 2010; Gerber et al., 2011; Kamio, Inada, & Koyama, 2013; Mahan & Kozlowski, 2011; Sheldrick, Neger, Shipman, & Perrin, 2012). Although educational and cognitive-behavioral programs are now accepted in most advanced countries as important to helping adults with ASD and ID improve their QoL (Gerber et al., 2011; Thorn, Bamburg, & Pittman, 2007), there is little research addressing co-morbid psychopathology associated with adults with ASD and ID (Kearney & Healy, 2011; Totsika, Felce, Kerr, & Hastings, 2010). However, some research has examined implications of challenging behaviors since these types of behaviors negatively impact a wide range of life domains (e.g., leisure, vocational, social) that influence QoL for people with ASD and ID (Hastings, 2002). There are a variety of co-morbid psychopathologies that exist with adults who have both an ASD and an ID. These adults have higher vulnerability for developing psychiatric disorders and behavioral challenges than those individuals who do not
* Corresponding author. E-mail addresses: [email protected] (D. Garcı´a-Villamisar), [email protected] (J. Dattilo), [email protected] (J.L. Matson). 1 Department of Personality and Clinical Psychology, Avda. Juan XXIII, sn, 28040 Madrid. Spain. Tel.: +34 913946123. 2 Department of Recreation, Park and Tourism Management, 801 Ford Building, Penn State University, University Park, PA 16802, United States. Tel.: +1 814 865 1851. 3 Department of Psychology, Louisiana State University, 234 Audubon Hall, Baton Rouge, LA 70803, United States. 1750-9467/$ – see front matter ß 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.rasd.2012.12.009
D. Garcı´a-Villamisar et al. / Research in Autism Spectrum Disorders 7 (2013) 624–629
625
have both of these disabling conditions (Ghaziuddin, 2005). More specifically, these individuals are at risk for behavior problems such as self-injurious actions, stereotyped movements, and aggressive/destructive behaviors, and other psychiatric conditions (Einfeld & Aman, 1995; Matson, Fodstad, & Rivet, 2009a; Matson, Rivet, Fodstad, Dempsey, & Boisjoli, 2009b; Smith & Matson, 2010; Tenneij, Didden, Stolker, & Koot, 2009). Although behavioral challenges are not pathognomonic symptoms of individuals with ASD and ID, several studies have demonstrated that approximately 13–30% of people with ASD and ID demonstrate some type of challenging behavior (Sturmey, Laud, Cooper, Matson, & Fodstad, 2010). As a result of these behavioral challenges and potential risk of injury, some adults reside in public or private residential facilities (Gerber et al., 2011; Rojahn & Meier, 2009; Rojahn & Tasse, 1996; Totsika et al., 2010). Such behavioral challenges often negatively influence the QoL of these individuals (Gerber, Baud, Giroud, & Carminati, 2008; Totsika et al., 2010). Since the early 1970s, interest in the concept of QoL has increased significantly, both in research and clinical practice and it has been increasingly applied to people with ASD (Billstedt et al., 2011: Cappe et al., 2011; Cottenceau et al., 2012; Gerber et al., 2011; Kamp-Becker, Schroder, Remschmidt, & Bachmann, 2010; Plimley, 2007; Shipman, Sheldrick, & Perrin, 2011; Totsika et al., 2010). QoL has emerged as an important parameter for evaluating the outcomes of health care and associated services (Moons, Budts, & De Geest, 2006), particularly for people with ASD (Johnson, Frenn, Feetham, & Simpson, 2011; Kamp-Becker et al., 2010; Kuhlthau et al., 2010; Moons et al., 2006) In the present study we explored the relationship between the level of QoL in a group of adults with ID and ASD and the severity of behavioral challenges. Our aim was to determine if these behavioral challenges were mediated by QoL over time. We hypothesized that a possible link exists between reduction in the severity of behavior problems and increase in QoL. 2. Method 2.1. Participants Participants included 70 adults between 18 and 43 years (M = 26.60; SD = 10.01) with ID and ASD. The average of Leiter Test was 53.39 (SD = 9.94). Participants were recruited from a facility for people with ASD located in Las Rozas, a residential community of Madrid, Spain and other institutions for people with ID. All participants were diagnosed with an ID and ASD by a psychiatrist or clinical psychologist with several years of diagnostic experience with people who have both an ID and ASD. Participants were screened to exclude co-morbid severe psychiatric illness (e.g., schizophrenia, anxiety, major depression) and neurological disorders that might influence brain functioning (e.g., epilepsy). The ethics commission of the Nuevo Horizonte Association reviewed and approved this study. An explanation of the study was given to participants, their tutors, and their families before the study was initiated. All participants or their guardians provided informed consent. Individuals for whom we could not obtain consent were excluded from the study. 2.2. Measures 2.2.1. Leiter International Performance Scale (LIPS) The LIPS (Leiter, 1980) is a non-verbal intelligence test designed for people between 2 and 18 years age, although it can be applied to all ages. No speech is required from the examiner or participant. The tasks are self-explanatory and, after an initial demonstration, the examiner does not need to interact with the subject. The LIPS is useful for testing people with ASD. The LIPS was scored according to the method outlined in the manual and was derived and adjusted as recommended by Leiter (1980). 2.2.2. Autism spectrum disorders–diagnosis for adults (ASD-DA) The ASD-DA (Matson & Rivet, 2007) is an instrument aimed at diagnosing ID adults with ASD and contains 31 items which are scored as either ‘‘0’’ for ‘‘not different, no impairment’’ or ‘‘1’’ for ‘‘different, some impairment.’’ The test can be administered in approximately 10 min. The ASD-DA has adequate inter-rater and test–retest reliabilities. Internal consistency was excellent (Cronbach’s a = .94), and factor analysis produced a three factor solution that mirrors the three classes of core symptoms outlined in the DSM-IV-TR (i.e., impairment in socialization, communication, and restricted behavior) (Matson, Gonzalez, Wilkins, & Rivet, 2008; Matson, Wilkins, Boisjoli, & Smith, 2008). Belva, Matson, Hattier, Kozlowski, and Bamburg (2012) investigated the validity of the ASD-DA when compared with the Pervasive Developmental Disorder/Autism subscale of the Diagnostic Assessment for the Severely Handicapped-II (DASH-II; Matson, Gardner, Coe, & Sovner, 1991). The total scores and subscale scores of the ASD-DA correlated at the p < .001 level with PDD/Autism subscale scores on the DASH-II. These findings suggest that the ASD-DA is a valid measure for assessing autistic symptoms in adults with IDs. 2.2.3. The autism spectrum disorders–behavior problems for adults (ASD-BPA) The ASD-BPA was planned as an informant-based behavioral screener and is the only assessment instrument developed to specifically measure challenging behaviors of adults with ASD (Matson & Rivet, 2007, 2008). The measure is comprised of 19 items rated on a Likert-type scale corresponding to different challenging behaviors commonly showed by adults with ASD. Initial psychometrics for the scale estimated that the ASD-BPA has internal reliability ranges from .43 to .83 for all subscales, average test–retest reliability approaches .60, and average inter-rater reliability is .43 (Matson & Rivet, 2008).
D. Garcı´a-Villamisar et al. / Research in Autism Spectrum Disorders 7 (2013) 624–629
626
2.2.4. Quality of life (QoL) questionnaire The QoL questionnaire (Schalock & Keith, 1993) has 40 criterion-referenced items, reflecting four domains of QoL – Satisfaction, Competence/Productivity, Empowerment/Independence and Social Belonging/Community Integration. Each question is measured on a 1- to 3-point Likert scale. The QoL scored index can range from 40 (low) to 120 (high). The QoL was translated to several cultures, such as Spanish (Caballo, Crespo, Jenaro, Verdugo, & Martinez, 2005), Chinese (Wong, Wong, Schalock, & Chou, 2011), Portuguese (Albuquerque, 2012), etc., and the psychometric proprieties are acceptable (Caballo et al., 2005; Kober & Eggleton, 2002; Wang, Schalock, Verdugo, & Jenaro, 2010). The measure can be completed by a proxy respondent or by the person with ASD or a combination of both. The Spanish version of the QoL questionnaire developed by Caballo et al. (2005) appears to fulfill the attributes for a valid assessment tool. 2.3. Procedures Prior to initiation of the study, the responsible ethics commission of the Nuevo Horizonte Association reviewed and approved this study. An explanation of the study was given to participants, their tutors, and their families before the study was initiated. Participants or their primary caregiver provided informed consent. Participants were recruited from a specialized residential community for individuals with ASD and other institutions for people with intellectual disabilities in Spain. Participants with adequate receptive or expressive verbal skills completed the battery of questionnaires by themselves (n = 6); a primary caregiver completed the instruments for those participants who did not have adequate verbal skills. 2.4. Statistical analyses All statistical analyses were performed with SPSS, version 19.0, for Windows (Copyright, SPSS Inc., 1989–2008). Correlation was computed for ASD traits (ASD-DA), problem behavior (ASD-PBA), and QoL (QOL). Then the testing of the multiple mediation hypotheses was conducted with SPSS macros for bootstrapping as provided by Preacher and Hayes
a1 = -.04**
Satisfaction
a2
= -.08***
a3
= -.12***
b1
Competence / Productivity
= -.43
b2
= -.41
b3
= -.45
b4
= -.11
Autonomy / Independence a4 = -.03
Community Involvement ID and ASD traits (IV)
c = .25
***
c’ = .14*
Behavior problems (DV)
a1 , a 2, a3, a4 = Direct effects of IV on mediators (a paths) b1, b2, b3, b4 = Direct effects of mediators on DV (b paths) c = Total effect of IV on DV (c path) c’ = Direct effect of IV on DV (c prime path) *p <.05; ** p< .01; ***p < .001 Fig. 1. Model of multiple mediation among intellectual disability and autism spectrum disorder traits (ID and ASD traits), behavior problems (DV), and dimensions of QoL (mediator variables).
D. Garcı´a-Villamisar et al. / Research in Autism Spectrum Disorders 7 (2013) 624–629
627
(2008). Total Score on Problem Behavior was used as the dependent variable (DV) and the Total Score on Autistic traits (ASDDA) as the independent variable (IV); Satisfaction, Competence/Productivity, Autonomy/Independence and Community Involvement were tested as multiple mediators (see Fig. 1). An initial causal variable X (IV) may influence an outcome variable Y (DV) through multiple mediators M1, M2, M3. . . Mn. Mediation occurs if the effect of X on Y is partly or entirely ‘‘transmitted’’ by multiple mediators Mn. Bootstrap procedures were used for mediational analyses since they are currently recommended as best practice with small sample sizes (e.g., Preacher & Hayes, 2008). The reported results are based upon bias corrected and accelerated (BCa) confidence intervals that were set at 95% with 5000 bootstrap samples to present the indirect effects’ significance. An indirect effect (total or specific) was considered to be significant if its 95% bootstrap CIs from 5000 samples did not include zero at a = .05. 3. Results 3.1. Correlational analysis To establish basic relationships between variables we first computed first-order correlations between IV, DV, and mediators. The means, standard deviations, and inter-correlations of ASD traits (ASD-DA), behavior problems (ASD-PBA), and the dimensions of QoL (Satisfaction, Competence/Productivity, Autonomy/Independence and Community Involvement) are presented in Table 1. Scores for ASD-DA were significantly and positively correlated with ESD-PBA total scores and the total score for ASD-PBA and ASD-DA were negatively correlated with dimensions of QoL. 3.2. Testing the multiple mediation model Results of the multiple mediation model indicated that when taken as set, dimensions of QoL mediate effects of ASD-DA on ASD-DA. As can be seen in Table 2, the total (c path) and direct effects (c’ path) of Total Score of Autistic traits on Total Score of Behavior Problems are .14 (p < .05) and .25 (p < .0001), respectively. The difference between the total and direct effects is the total indirect effects through the three mediators with a point estimate of .11 and a 95% BCa bootstrap CI of .05 to .18. We have 95% confidence that, because zero is not within this interval, zero is not likely a value for the indirect effect of Total Score of Autistics traits on Total Score of Behavior Problems. The true indirect effect is estimated to lie between .05 and 0.18. An analysis of the specific indirect effects indicates that the dimensions of QoL (Satisfaction, Competence/Productivity and Autonomy/Independence) are mediators since its 95% CI does not contain zero. However, the dimension Community/ Involvement does not contribute to the indirect effect.
Table 1 Pearson correlation between behavior problems, ASD traits, and QoL assessments of adults with ASD and ID. 2 1 2 3 4 5 6
ASD-DA total score ASD-PBA total score QOL-satisfaction QOL-competence/productivity QOL-autonomy/independence QOL-community involvement
.61** –
3
4
5
.28* .26* –
.42** .37** .05 –
.64** .49** .14 .14 –
6 .17 .18 .39** .20 .49** –
Mean
SD
36.07 5.56 22.20 15.94 15.26 19.11
17.57 7.19 2.72 3.52 3.26 2.83
* p < .05. ** p < .01.
Table 2 Summary of multiple mediator model analysis of ASD traits on behavior problems through QoL dimensions.
Total Satisfaction Competence/productivity Autonomy/independence community involvement a
Effects of IV on M
Effects of M on DV
Direct effects
(a path)
(b path)
c’ path .19*
.04** .08*** .12*** .03
.43 .41 .45 .11
BCa, bias corrected and accelerated confidence intervals; 5000 bootstrap samples. * p < .05. ** p < .01. *** p < .001.
Point estimate
.11 .02 .03 .05 .01
Indirect effects (ab paths) BCa 95% CIa
Total effect
Lower
Upper
c path
.18 .05 .07 .10 .03
.25***
.05 .05 .01 .05 .01
628
D. Garcı´a-Villamisar et al. / Research in Autism Spectrum Disorders 7 (2013) 624–629
4. Discussion The presence of challenging behaviors is one of the most significant variables affecting the QoL of individuals with ID and ASD and their caregivers (Gardner, Graeber-Whalen, & Ford, 2001). These challenging behaviors can present substantial risks to people’s health and their QoL. For those with an ID and an ASD, a challenging behavior can further impede daily functioning, given the symptomatology associated with ID and ASD (Matson et al., 2012; Matson & Rivet, 2008). The purpose of this study was to investigate the mediation of quality of life between challenging behaviors and symptomatology of individuals with ID and ASD. The correlational analysis revealed a positive relation between ASD symptomatology and challenging behaviors in line with recent research (e.g., Bihm, Poindexter, & Warren, 1998; Emerson et al., 2001; Matson et al., 2012; Matson, Minshawi, Gonza´lez, & Mayville, 2006). Conversely, QoL was negatively correlated with the ASD and challenging behaviors. In relation to the QoL of adults with ID and ASD there is a paucity of research findings (Perry & Felce, 2002; Totsika et al., 2010), because the subjective satisfaction represents a methodological challenge in this type of population. The presence of symptoms of ASD and behavior problems is related to lower ratings of QoL. In addition, this study demonstrated that several dimensions of QoL mediated the relationships between ASD traits and challenging behaviors. The dimensions of QoL, Satisfaction, Competence/Productivity, and Autonomy/Independence are mediators between ASD traits and challenging behaviors. Thus, a focus on identifying and increasing QoL appears to be of considerable importance to addressing the relationship between ASD traits and behavior problems. In addition to the mediating variables examined in this study, there are other potential mediating variables contributing to the relationship between challenging behaviors and autistic traits that merit exploration. Intellectual level, age, social competence or comorbid psychopathology may be candidates for exploration in this context. 4.1. Limitations and future recommendations This study had some limitations that must be mentioned. Our data collection was cross-sectional (the assessment occurred at a single point in time) and, therefore, our inferences regarding developmental trajectories are limited. Given the research that suggests the changing phenomenology of challenging behaviors over time (e.g., Matson et al., 2011), future research is warranted that examines these findings across different age groups longitudinally. Also, since the sample primarily consisted of adults with ASD and ID, our sample was not representative of the entire ASD population. Research that includes individuals with autism or Asperger’s disorder who do not have an ID may provide further insights. Furthermore, due to the inherent challenges associated with the cross-sectional nature of the data, there is merit in designing longitudinal research to examine this issue. Finally, given the inconsistency that occurred with some participants independently completing the questionnaires and primary caregivers completing the questionnaire on behalf of other individuals, further research that relies on systematic data collection procedures may be useful. 4.2. Conclusion Even with these limitations, the proposed multiple mediator model was significant with several dimensions of QoL mediating the relationship between challenging behaviors and ASD traits. Clinically, the current study has implications for practitioners working with people with ASD who demonstrate challenging behaviors. Findings support the conclusion that enhancement of the QoL of adults with ASD will occur with a reduction in behavior problems. Further research should focus on determining how to design programs that enhance QoL and to evaluate the impact of such programs on externalizing or internalizing behaviors and specific ASD psychopathology. Acknowledgements The essential contribution of the therapeutic staff of Nuevo Horizonte Association and the individuals with autism and intellectual disability who participated in this study is gratefully appreciated. References Albuquerque, C. P. (2012). Psychometric properties of the Portuguese version of the Quality of Life Questionnaire (QOL-Q). Journal of Applied Research in Intellectual Disabilities, 25(5), 445–454. Belva, B. C., Matson, J. L., Hattier, M. A., Kozlowski, A. M., & Bamburg, J. W. (2012). Convergent validity of the Autism Spectrum Disorders–Diagnostic Adult (ASDDA) with the Pervasive Developmental Disorder/Autism subscale of the Diagnostic Assessment for the Severely Handicapped-II (DASH-II). Research in Autism Spectrum Disorders, 6, 752–756. Bihm, E. M., Poindexter, A. R., & Warren, E. R. (1998). Aggression and psychopathology in persons with severe or profound mental retardation. Research in Developmental Disabilities, 19(5), 423–438. Billstedt, E., Gillberg, I. C., & Gillberg, C. (2011). Aspects of quality of life in adults diagnosed with autism in childhood: A population-based study. Autism, 15(1), 7–20. Caballo, C., Crespo, C., Jenaro, C., Verdugo, M. A., & Martinez, J. L. (2005). Factor structure of the Schalock and Keith Quality of life Questionnaire (QOL-Q): Validation on Mexican and Spanish samples. Journal of Intellectual Disability Research, 49, 773–776. Cappe, E., Wolff, M., Bobet, R., & Adrien, J. L. (2011). Quality of life: A key variable to consider in the evaluation of adjustment in parents of children with autism spectrum disorders and in the development of relevant support and assistance programmes. Quality Life Research, 20(8), 1279–1294. Cottenceau, H., Roux, S., Blanc, R., Lenoir, P., Bonnet-Brilhault, F., & Barthelemy, C. (2012). Quality of life of adolescents with autism spectrum disorders: comparison to adolescents with diabetes. European Child and Adolescent Psychiatry, 21(5), 289–296.
D. Garcı´a-Villamisar et al. / Research in Autism Spectrum Disorders 7 (2013) 624–629
629
Einfeld, S. L., & Aman, M. (1995). Issues in the taxonomy of psychopathology in mental retardation. Journal of Autism and Developmental Disorder, 25, 143–167. Emerson, E., Kiernan, C., Alborz, A., Reeves, D., Mason, H., Swarbrick, R., et al. (2001). The prevalence of challenging behaviors: A total population study. Research in Developmental Disabilities, 22(1), 77–93. Garcia-Villamisar, D. A., & Dattilo, J. (2010). Effects of a leisure program on quality of life and stress of individuals with ASD. Journal of Intellectual and Disability Research, 54(7), 611–619. Gardner, W. I., Graeber-Whalen, J. L., & Ford, D. R. (2001). Self-injurious behaviors: Multimodal contextual approach to treatment. In A. Dosen & K. Day (Eds.), Treating mental illness and behavior disorders in children and adults with mental retardation (pp. 323–357). Washington, DC: American Psychiatric Press, Inc. Gerber, F., Baud, M. A., Giroud, M., & Carminati, G. G. (2008). Quality of life of adults with pervasive developmental disorders and intellectual disabilities. Journal of Autism and Developmental Disorders, 38, 1654–1665. Gerber, F., Bessero, S., Robbiani, B., Courvoisier, D. S., Baud, M. A., Traore, M. C., et al. (2011). Comparing residential programmes for adults with autism spectrum disorders and intellectual disability: Outcomes of challenging behaviour and quality of life. Journal of Intellectual Disability Research, 55(9), 918–932. Ghaziuddin, M. (2005). A family history study of Asperger syndrome. Journal of Autism and Developmental Disorders, 35(2), 177–182. Hastings, R. P. (2002). Do challenging behaviors affect staff psychological well-being? Issues of causality and mechanism. American Journal of Mental Retardation, 107(6), 555–567. Johnson, N., Frenn, M., Feetham, S., & Simpson, P. (2011). Autism spectrum disorder: parenting stress, family functioning and health-related quality of life. Families, Systems and Health, 29(3), 232–252. Kamio, Y., Inada, N., & Koyama, T. (2013). A nationwide survey on quality of life and associated factors of adults with high-functioning autism spectrum disorders. Autism, 17(1), 15–26. Kamp-Becker, I., Schroder, J., Remschmidt, H., & Bachmann, C. J. (2010). Health-related quality of life in adolescents and young adults with high functioning autism-spectrum disorder. Psycho-Social-Medicine, 7, 1–10. Kearney, D. S., & Healy, O. (2011). Investigating the relationship between challenging behavior, co-morbid psychopathology and social skills in adults with moderate to severe intellectual disabilities in Ireland. Research in Developmental Disabilities, 32(5), 1556–1563. Kober, R., & Eggleton, I. R. (2002). Factor stability of the Schalock and Keith (1993) Quality of Life Questionnaire. Mental Retardation, 40(2), 157–165. Kuhlthau, K., Orlich, F., Hall, T. A., Sikora, D., Kovacs, E. A., Delahaye, J., et al. (2010). Health-related quality of life in children with autism spectrum disorders: Results from the autism treatment network. Journal of Autism and Developmental Disorders, 40(6), 721–729. Leiter, R. G. (1980). Leiter International Performance Scale, instruction manual. Chicago: Stoelting. Mahan, S., & Kozlowski, A. M. (2011). Adults with autism spectrum disorders. In J. L. Matson & P. Sturmey (Eds.), Handbook of autism and pervasive developmental (pp. 521–539). New York: Springer International. Matson, J. L., Fodstad, J. C., & Rivet, T. T. (2009). The relationship of social skills and problem behaviors in adults with intellectual disability and autism or PDD-NOS. Research in Autism Spectrum Disorders, 3, 256–268. Matson, J. L., Gardner, W. I., Coe, D. A., & Sovner, R. (1991). A scale for evaluating emotional disorders in severely and profoundly retarded persons: Developmental of the Diagnostic Assessment for the Severely Handicapped (DASH-II). Research in Developmental Disabilities, 18, 457–469. Matson, J. L., Gonzalez, M. L., Wilkins, J., & Rivet, T. T. (2008). Reliability of the autism spectrum disorder–diagnostic for children (ASD-DC). Research in Autism Spectrum Disorders, 2(3), 533–545. Matson, J. L., Kozlowski, A. M., Worley, J. A., Shoemaker, M. E., Sipes, M., & Horovitz, M. (2011). What is the evidence for environmental causes of challenging behaviors in persons with intellectual disabilities and autism spectrum disorders? Research in Developmental Disabilities, 32(2), 693–698. Matson, J. L., Minshawi, N. F., Gonza´lez, M. L., & Mayville, S. B. (2006). The relationship of comorbid problem behaviors to social skills in persons with profound mental retardation. Behavior Modification, 30, 496–506. Matson, J. L., & Rivet, T. T. (2007). A validity study of the Autism Spectrum Disorders–Behavior Problems for Adults (ASD-BPA) scale. Journal of Developmental and Physical Disabilities, 19, 557–564. Matson, J. L., & Rivet, T. T. (2008). Reliability and factor structure of the Autism Spectrum Disorders–Behavior Problems for Adults (ASD-BPA) with intellectual disabilities. Research in Developmental Disabilities, 1, 34–47. Matson, J. L., Rivet, T. T., Fodstad, J. C., Dempsey, T., & Boisjoli, J. A. (2009). Examination of adaptive behavior differences in adults with autism spectrum disorders and intellectual disability. Research in Developmental Disabilities, 30(6), 1317–1325. Matson, J. L., & Shoemaker, M. (2009). Intellectual disability and its relationship to autism spectrum disorders. Research in Developmental Disabilities, 30(6), 1107– 1114. Matson, J. L., Wilkins, J., Boisjoli, J. A., & Smith, K. R. (2008). The validity of the autism spectrum disorders–diagnosis for intellectually disabled adults (ASD-DA). Research in Developmental Disabilities, 29, 537–546. Matson, J. L., & Turygin, N. C. (2012). How do researchers define self-injurious behavior? Research In Developmental Disabilities, 33(4), 1021–1026. Moons, P., Budts, W., & De Geest, S. (2006). Critique on the conceptualisation of quality of life: A review and evaluation of different conceptual approaches. International Journal of Nursing Studies, 43(7), 891–901. Perry, J., & Felce, D. (2002). Subjective and objective quality of life assessment: Responsiveness, response bias, and resident: Proxy concordance. Mental Retardation, 40(6), 445–456. Plimley, L. A. (2007). A review of quality of life issues and people with autism spectrum disorders. British Journal of Learning Disabilities, 35, 205–213. Preacher, K. J., & Hayes, A. F. (2008). Asymptotic and resampling strategies for assessing and comparing indirect effects in multiple mediator models. Behavior Research Methods, 40, 879–891. Rojahn, J., & Meier, L. J. (2009). Chapter nine – Epidemiology of mental illness and maladaptive behavior in intellectual disabilities. International review of research in mental retardation, 38, 239–287. Rojahn, J., & Tasse, M. J. (1996). Psychopathology in mental retardation. In J. W. Jacobson & J. A. Mulick (Eds.), Manual of diagnosis and professional practice in mental retardation. Washington, DC: American Psychological Association. Schalock, R. L., & Keith, K. D. (1993). Quality of life questionnaire manual. Ohio: IDS Publishing Corporation. Sheldrick, R. C., Neger, E. N., Shipman, D., & Perrin, E. C. (2012). Quality of life of adolescents with autism spectrum disorders: concordance among adolescents’ selfreports, parents’ reports, and parents’ proxy reports. Qual of Life Research, 21(1), 53–57. Shipman, D. L., Sheldrick, R. C., & Perrin, E. C. (2011). Quality of life in adolescents with autism spectrum disorders: Reliability and validity of self-reports. Journal of Developmental & Behavioral Pediatrics, 32(2), 85–89. Smith, K. R. M., & Matson, J. L. (2010). Behavior problems: Differences among intellectually disabled adults with co-morbid autism spectrum disorders and epilepsy. Research in Developmental Disabilities, 31(5), 1062–1069. Sturmey, P., Laud, R. B., Cooper, C. L., Matson, J. L., & Fodstad, J. C. (2010). Challenging behaviors should not be considered depressive equivalents in individuals with intellectual disabilities. II. A replication study. Research in Developmental Disabilities, 31, 1002–1007. Tenneij, N. H., Didden, R., Stolker, J. J., & Koot, H. M. (2009). Markers for aggression in inpatient treatment facilities for adults with mild to borderline intellectual disability. Research in Developmental Disabilities, 30, 1248–1254. Thorn, S. H., Bamburg, J. W., & Pittman, A. (2007). Psychosocial treatment malls for people with intellectual disabilities. Research in Developmental Disabilities, 28(5), 531–538. Totsika, V., Felce, D., Kerr, M., & Hastings, R. P. (2010). Behavior problems, psychiatric symptoms, and quality of life for older adults with intellectual disability with and without autism. Journal of Autism and Developmental Disorders, 40(10), 1171–1178. Wang, M., Schalock, R. L., Verdugo, M. A., & Jenaro, C. (2010). Examining the factor structure and hierarchical nature of the quality of life construct. American Journal on Intellectual and Developmental Disabilities, 115(3), 218–233. Wong, P. K., Wong, D. F., Schalock, R. L., & Chou, Y. C. (2011). Initial validation of the Chinese Quality of Life Questionnaire–Intellectual Disabilities (CQOL-ID): A cultural perspective. Journal of Intellectual Disability Research, 55(6), 572–580.
Contents lists available at SciVerse ScienceDirect
Research in Autism Spectrum Disorders Journal homepage: http://ees.elsevier.com/RASD/default.asp
Quality of life as a mediator between behavioral challenges and autistic traits for adults with intellectual disabilities Domingo Garcı´a-Villamisar a,1,*, John Dattilo b,2, Johnny L. Matson c,3 a
Complutense University of Madrid, Spain Penn State University, USA c Louisiana State University, USA b
A R T I C L E I N F O
A B S T R A C T
Article history: Received 26 November 2012 Accepted 29 December 2012
A multiple mediation model was proposed to integrate core concepts of challenging behaviors with autistic traits to increase understanding of their relationship to quality of life (QoL). It was hypothesized that QoL is a possible mediator between the severity of challenging behaviors and autistic traits in adults with intellectual disability. These constructs are of vital importance because they are essential variables for people with autism, and obviously they influence their psychosocial development. Participants were 70 adults with autism spectrum disorders (ASD) and moderate intellectual disabilities (ID). Results indicated that several dimensions of QoL mediated the relationships between autistic traits and challenging behaviors. The dimensions of QoL, Satisfaction, Competence/Productivity, and Autonomy/Independence are mediators between autistic traits and challenging behaviors. Implications of these data are discussed. ß 2013 Elsevier Ltd. All rights reserved.
Keywords: Autism spectrum disorders Intellectual disabilities Behavioral challenges Quality of life
1. Introduction Autism spectrum disorders (ASD) and intellectual disabilities (ID) often co-occur at high rates with the relationship between the two disorders being enigmatic (Matson & Shoemaker, 2009). With the increase in life expectancy in occidental societies, the concern for promoting a positive quality of life (QoL) for adults who have both ASD and ID is growing (Billstedt, Gillberg, & Gillberg, 2011; Cappe, Wolff, Bobet, & Adrien, 2011; Cottenceau et al., 2012; Garcia-Villamisar & Dattilo, 2010; Gerber et al., 2011; Kamio, Inada, & Koyama, 2013; Mahan & Kozlowski, 2011; Sheldrick, Neger, Shipman, & Perrin, 2012). Although educational and cognitive-behavioral programs are now accepted in most advanced countries as important to helping adults with ASD and ID improve their QoL (Gerber et al., 2011; Thorn, Bamburg, & Pittman, 2007), there is little research addressing co-morbid psychopathology associated with adults with ASD and ID (Kearney & Healy, 2011; Totsika, Felce, Kerr, & Hastings, 2010). However, some research has examined implications of challenging behaviors since these types of behaviors negatively impact a wide range of life domains (e.g., leisure, vocational, social) that influence QoL for people with ASD and ID (Hastings, 2002). There are a variety of co-morbid psychopathologies that exist with adults who have both an ASD and an ID. These adults have higher vulnerability for developing psychiatric disorders and behavioral challenges than those individuals who do not
* Corresponding author. E-mail addresses: [email protected] (D. Garcı´a-Villamisar), [email protected] (J. Dattilo), [email protected] (J.L. Matson). 1 Department of Personality and Clinical Psychology, Avda. Juan XXIII, sn, 28040 Madrid. Spain. Tel.: +34 913946123. 2 Department of Recreation, Park and Tourism Management, 801 Ford Building, Penn State University, University Park, PA 16802, United States. Tel.: +1 814 865 1851. 3 Department of Psychology, Louisiana State University, 234 Audubon Hall, Baton Rouge, LA 70803, United States. 1750-9467/$ – see front matter ß 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.rasd.2012.12.009
D. Garcı´a-Villamisar et al. / Research in Autism Spectrum Disorders 7 (2013) 624–629
625
have both of these disabling conditions (Ghaziuddin, 2005). More specifically, these individuals are at risk for behavior problems such as self-injurious actions, stereotyped movements, and aggressive/destructive behaviors, and other psychiatric conditions (Einfeld & Aman, 1995; Matson, Fodstad, & Rivet, 2009a; Matson, Rivet, Fodstad, Dempsey, & Boisjoli, 2009b; Smith & Matson, 2010; Tenneij, Didden, Stolker, & Koot, 2009). Although behavioral challenges are not pathognomonic symptoms of individuals with ASD and ID, several studies have demonstrated that approximately 13–30% of people with ASD and ID demonstrate some type of challenging behavior (Sturmey, Laud, Cooper, Matson, & Fodstad, 2010). As a result of these behavioral challenges and potential risk of injury, some adults reside in public or private residential facilities (Gerber et al., 2011; Rojahn & Meier, 2009; Rojahn & Tasse, 1996; Totsika et al., 2010). Such behavioral challenges often negatively influence the QoL of these individuals (Gerber, Baud, Giroud, & Carminati, 2008; Totsika et al., 2010). Since the early 1970s, interest in the concept of QoL has increased significantly, both in research and clinical practice and it has been increasingly applied to people with ASD (Billstedt et al., 2011: Cappe et al., 2011; Cottenceau et al., 2012; Gerber et al., 2011; Kamp-Becker, Schroder, Remschmidt, & Bachmann, 2010; Plimley, 2007; Shipman, Sheldrick, & Perrin, 2011; Totsika et al., 2010). QoL has emerged as an important parameter for evaluating the outcomes of health care and associated services (Moons, Budts, & De Geest, 2006), particularly for people with ASD (Johnson, Frenn, Feetham, & Simpson, 2011; Kamp-Becker et al., 2010; Kuhlthau et al., 2010; Moons et al., 2006) In the present study we explored the relationship between the level of QoL in a group of adults with ID and ASD and the severity of behavioral challenges. Our aim was to determine if these behavioral challenges were mediated by QoL over time. We hypothesized that a possible link exists between reduction in the severity of behavior problems and increase in QoL. 2. Method 2.1. Participants Participants included 70 adults between 18 and 43 years (M = 26.60; SD = 10.01) with ID and ASD. The average of Leiter Test was 53.39 (SD = 9.94). Participants were recruited from a facility for people with ASD located in Las Rozas, a residential community of Madrid, Spain and other institutions for people with ID. All participants were diagnosed with an ID and ASD by a psychiatrist or clinical psychologist with several years of diagnostic experience with people who have both an ID and ASD. Participants were screened to exclude co-morbid severe psychiatric illness (e.g., schizophrenia, anxiety, major depression) and neurological disorders that might influence brain functioning (e.g., epilepsy). The ethics commission of the Nuevo Horizonte Association reviewed and approved this study. An explanation of the study was given to participants, their tutors, and their families before the study was initiated. All participants or their guardians provided informed consent. Individuals for whom we could not obtain consent were excluded from the study. 2.2. Measures 2.2.1. Leiter International Performance Scale (LIPS) The LIPS (Leiter, 1980) is a non-verbal intelligence test designed for people between 2 and 18 years age, although it can be applied to all ages. No speech is required from the examiner or participant. The tasks are self-explanatory and, after an initial demonstration, the examiner does not need to interact with the subject. The LIPS is useful for testing people with ASD. The LIPS was scored according to the method outlined in the manual and was derived and adjusted as recommended by Leiter (1980). 2.2.2. Autism spectrum disorders–diagnosis for adults (ASD-DA) The ASD-DA (Matson & Rivet, 2007) is an instrument aimed at diagnosing ID adults with ASD and contains 31 items which are scored as either ‘‘0’’ for ‘‘not different, no impairment’’ or ‘‘1’’ for ‘‘different, some impairment.’’ The test can be administered in approximately 10 min. The ASD-DA has adequate inter-rater and test–retest reliabilities. Internal consistency was excellent (Cronbach’s a = .94), and factor analysis produced a three factor solution that mirrors the three classes of core symptoms outlined in the DSM-IV-TR (i.e., impairment in socialization, communication, and restricted behavior) (Matson, Gonzalez, Wilkins, & Rivet, 2008; Matson, Wilkins, Boisjoli, & Smith, 2008). Belva, Matson, Hattier, Kozlowski, and Bamburg (2012) investigated the validity of the ASD-DA when compared with the Pervasive Developmental Disorder/Autism subscale of the Diagnostic Assessment for the Severely Handicapped-II (DASH-II; Matson, Gardner, Coe, & Sovner, 1991). The total scores and subscale scores of the ASD-DA correlated at the p < .001 level with PDD/Autism subscale scores on the DASH-II. These findings suggest that the ASD-DA is a valid measure for assessing autistic symptoms in adults with IDs. 2.2.3. The autism spectrum disorders–behavior problems for adults (ASD-BPA) The ASD-BPA was planned as an informant-based behavioral screener and is the only assessment instrument developed to specifically measure challenging behaviors of adults with ASD (Matson & Rivet, 2007, 2008). The measure is comprised of 19 items rated on a Likert-type scale corresponding to different challenging behaviors commonly showed by adults with ASD. Initial psychometrics for the scale estimated that the ASD-BPA has internal reliability ranges from .43 to .83 for all subscales, average test–retest reliability approaches .60, and average inter-rater reliability is .43 (Matson & Rivet, 2008).
D. Garcı´a-Villamisar et al. / Research in Autism Spectrum Disorders 7 (2013) 624–629
626
2.2.4. Quality of life (QoL) questionnaire The QoL questionnaire (Schalock & Keith, 1993) has 40 criterion-referenced items, reflecting four domains of QoL – Satisfaction, Competence/Productivity, Empowerment/Independence and Social Belonging/Community Integration. Each question is measured on a 1- to 3-point Likert scale. The QoL scored index can range from 40 (low) to 120 (high). The QoL was translated to several cultures, such as Spanish (Caballo, Crespo, Jenaro, Verdugo, & Martinez, 2005), Chinese (Wong, Wong, Schalock, & Chou, 2011), Portuguese (Albuquerque, 2012), etc., and the psychometric proprieties are acceptable (Caballo et al., 2005; Kober & Eggleton, 2002; Wang, Schalock, Verdugo, & Jenaro, 2010). The measure can be completed by a proxy respondent or by the person with ASD or a combination of both. The Spanish version of the QoL questionnaire developed by Caballo et al. (2005) appears to fulfill the attributes for a valid assessment tool. 2.3. Procedures Prior to initiation of the study, the responsible ethics commission of the Nuevo Horizonte Association reviewed and approved this study. An explanation of the study was given to participants, their tutors, and their families before the study was initiated. Participants or their primary caregiver provided informed consent. Participants were recruited from a specialized residential community for individuals with ASD and other institutions for people with intellectual disabilities in Spain. Participants with adequate receptive or expressive verbal skills completed the battery of questionnaires by themselves (n = 6); a primary caregiver completed the instruments for those participants who did not have adequate verbal skills. 2.4. Statistical analyses All statistical analyses were performed with SPSS, version 19.0, for Windows (Copyright, SPSS Inc., 1989–2008). Correlation was computed for ASD traits (ASD-DA), problem behavior (ASD-PBA), and QoL (QOL). Then the testing of the multiple mediation hypotheses was conducted with SPSS macros for bootstrapping as provided by Preacher and Hayes
a1 = -.04**
Satisfaction
a2
= -.08***
a3
= -.12***
b1
Competence / Productivity
= -.43
b2
= -.41
b3
= -.45
b4
= -.11
Autonomy / Independence a4 = -.03
Community Involvement ID and ASD traits (IV)
c = .25
***
c’ = .14*
Behavior problems (DV)
a1 , a 2, a3, a4 = Direct effects of IV on mediators (a paths) b1, b2, b3, b4 = Direct effects of mediators on DV (b paths) c = Total effect of IV on DV (c path) c’ = Direct effect of IV on DV (c prime path) *p <.05; ** p< .01; ***p < .001 Fig. 1. Model of multiple mediation among intellectual disability and autism spectrum disorder traits (ID and ASD traits), behavior problems (DV), and dimensions of QoL (mediator variables).
D. Garcı´a-Villamisar et al. / Research in Autism Spectrum Disorders 7 (2013) 624–629
627
(2008). Total Score on Problem Behavior was used as the dependent variable (DV) and the Total Score on Autistic traits (ASDDA) as the independent variable (IV); Satisfaction, Competence/Productivity, Autonomy/Independence and Community Involvement were tested as multiple mediators (see Fig. 1). An initial causal variable X (IV) may influence an outcome variable Y (DV) through multiple mediators M1, M2, M3. . . Mn. Mediation occurs if the effect of X on Y is partly or entirely ‘‘transmitted’’ by multiple mediators Mn. Bootstrap procedures were used for mediational analyses since they are currently recommended as best practice with small sample sizes (e.g., Preacher & Hayes, 2008). The reported results are based upon bias corrected and accelerated (BCa) confidence intervals that were set at 95% with 5000 bootstrap samples to present the indirect effects’ significance. An indirect effect (total or specific) was considered to be significant if its 95% bootstrap CIs from 5000 samples did not include zero at a = .05. 3. Results 3.1. Correlational analysis To establish basic relationships between variables we first computed first-order correlations between IV, DV, and mediators. The means, standard deviations, and inter-correlations of ASD traits (ASD-DA), behavior problems (ASD-PBA), and the dimensions of QoL (Satisfaction, Competence/Productivity, Autonomy/Independence and Community Involvement) are presented in Table 1. Scores for ASD-DA were significantly and positively correlated with ESD-PBA total scores and the total score for ASD-PBA and ASD-DA were negatively correlated with dimensions of QoL. 3.2. Testing the multiple mediation model Results of the multiple mediation model indicated that when taken as set, dimensions of QoL mediate effects of ASD-DA on ASD-DA. As can be seen in Table 2, the total (c path) and direct effects (c’ path) of Total Score of Autistic traits on Total Score of Behavior Problems are .14 (p < .05) and .25 (p < .0001), respectively. The difference between the total and direct effects is the total indirect effects through the three mediators with a point estimate of .11 and a 95% BCa bootstrap CI of .05 to .18. We have 95% confidence that, because zero is not within this interval, zero is not likely a value for the indirect effect of Total Score of Autistics traits on Total Score of Behavior Problems. The true indirect effect is estimated to lie between .05 and 0.18. An analysis of the specific indirect effects indicates that the dimensions of QoL (Satisfaction, Competence/Productivity and Autonomy/Independence) are mediators since its 95% CI does not contain zero. However, the dimension Community/ Involvement does not contribute to the indirect effect.
Table 1 Pearson correlation between behavior problems, ASD traits, and QoL assessments of adults with ASD and ID. 2 1 2 3 4 5 6
ASD-DA total score ASD-PBA total score QOL-satisfaction QOL-competence/productivity QOL-autonomy/independence QOL-community involvement
.61** –
3
4
5
.28* .26* –
.42** .37** .05 –
.64** .49** .14 .14 –
6 .17 .18 .39** .20 .49** –
Mean
SD
36.07 5.56 22.20 15.94 15.26 19.11
17.57 7.19 2.72 3.52 3.26 2.83
* p < .05. ** p < .01.
Table 2 Summary of multiple mediator model analysis of ASD traits on behavior problems through QoL dimensions.
Total Satisfaction Competence/productivity Autonomy/independence community involvement a
Effects of IV on M
Effects of M on DV
Direct effects
(a path)
(b path)
c’ path .19*
.04** .08*** .12*** .03
.43 .41 .45 .11
BCa, bias corrected and accelerated confidence intervals; 5000 bootstrap samples. * p < .05. ** p < .01. *** p < .001.
Point estimate
.11 .02 .03 .05 .01
Indirect effects (ab paths) BCa 95% CIa
Total effect
Lower
Upper
c path
.18 .05 .07 .10 .03
.25***
.05 .05 .01 .05 .01
628
D. Garcı´a-Villamisar et al. / Research in Autism Spectrum Disorders 7 (2013) 624–629
4. Discussion The presence of challenging behaviors is one of the most significant variables affecting the QoL of individuals with ID and ASD and their caregivers (Gardner, Graeber-Whalen, & Ford, 2001). These challenging behaviors can present substantial risks to people’s health and their QoL. For those with an ID and an ASD, a challenging behavior can further impede daily functioning, given the symptomatology associated with ID and ASD (Matson et al., 2012; Matson & Rivet, 2008). The purpose of this study was to investigate the mediation of quality of life between challenging behaviors and symptomatology of individuals with ID and ASD. The correlational analysis revealed a positive relation between ASD symptomatology and challenging behaviors in line with recent research (e.g., Bihm, Poindexter, & Warren, 1998; Emerson et al., 2001; Matson et al., 2012; Matson, Minshawi, Gonza´lez, & Mayville, 2006). Conversely, QoL was negatively correlated with the ASD and challenging behaviors. In relation to the QoL of adults with ID and ASD there is a paucity of research findings (Perry & Felce, 2002; Totsika et al., 2010), because the subjective satisfaction represents a methodological challenge in this type of population. The presence of symptoms of ASD and behavior problems is related to lower ratings of QoL. In addition, this study demonstrated that several dimensions of QoL mediated the relationships between ASD traits and challenging behaviors. The dimensions of QoL, Satisfaction, Competence/Productivity, and Autonomy/Independence are mediators between ASD traits and challenging behaviors. Thus, a focus on identifying and increasing QoL appears to be of considerable importance to addressing the relationship between ASD traits and behavior problems. In addition to the mediating variables examined in this study, there are other potential mediating variables contributing to the relationship between challenging behaviors and autistic traits that merit exploration. Intellectual level, age, social competence or comorbid psychopathology may be candidates for exploration in this context. 4.1. Limitations and future recommendations This study had some limitations that must be mentioned. Our data collection was cross-sectional (the assessment occurred at a single point in time) and, therefore, our inferences regarding developmental trajectories are limited. Given the research that suggests the changing phenomenology of challenging behaviors over time (e.g., Matson et al., 2011), future research is warranted that examines these findings across different age groups longitudinally. Also, since the sample primarily consisted of adults with ASD and ID, our sample was not representative of the entire ASD population. Research that includes individuals with autism or Asperger’s disorder who do not have an ID may provide further insights. Furthermore, due to the inherent challenges associated with the cross-sectional nature of the data, there is merit in designing longitudinal research to examine this issue. Finally, given the inconsistency that occurred with some participants independently completing the questionnaires and primary caregivers completing the questionnaire on behalf of other individuals, further research that relies on systematic data collection procedures may be useful. 4.2. Conclusion Even with these limitations, the proposed multiple mediator model was significant with several dimensions of QoL mediating the relationship between challenging behaviors and ASD traits. Clinically, the current study has implications for practitioners working with people with ASD who demonstrate challenging behaviors. Findings support the conclusion that enhancement of the QoL of adults with ASD will occur with a reduction in behavior problems. Further research should focus on determining how to design programs that enhance QoL and to evaluate the impact of such programs on externalizing or internalizing behaviors and specific ASD psychopathology. Acknowledgements The essential contribution of the therapeutic staff of Nuevo Horizonte Association and the individuals with autism and intellectual disability who participated in this study is gratefully appreciated. References Albuquerque, C. P. (2012). Psychometric properties of the Portuguese version of the Quality of Life Questionnaire (QOL-Q). Journal of Applied Research in Intellectual Disabilities, 25(5), 445–454. Belva, B. C., Matson, J. L., Hattier, M. A., Kozlowski, A. M., & Bamburg, J. W. (2012). Convergent validity of the Autism Spectrum Disorders–Diagnostic Adult (ASDDA) with the Pervasive Developmental Disorder/Autism subscale of the Diagnostic Assessment for the Severely Handicapped-II (DASH-II). Research in Autism Spectrum Disorders, 6, 752–756. Bihm, E. M., Poindexter, A. R., & Warren, E. R. (1998). Aggression and psychopathology in persons with severe or profound mental retardation. Research in Developmental Disabilities, 19(5), 423–438. Billstedt, E., Gillberg, I. C., & Gillberg, C. (2011). Aspects of quality of life in adults diagnosed with autism in childhood: A population-based study. Autism, 15(1), 7–20. Caballo, C., Crespo, C., Jenaro, C., Verdugo, M. A., & Martinez, J. L. (2005). Factor structure of the Schalock and Keith Quality of life Questionnaire (QOL-Q): Validation on Mexican and Spanish samples. Journal of Intellectual Disability Research, 49, 773–776. Cappe, E., Wolff, M., Bobet, R., & Adrien, J. L. (2011). Quality of life: A key variable to consider in the evaluation of adjustment in parents of children with autism spectrum disorders and in the development of relevant support and assistance programmes. Quality Life Research, 20(8), 1279–1294. Cottenceau, H., Roux, S., Blanc, R., Lenoir, P., Bonnet-Brilhault, F., & Barthelemy, C. (2012). Quality of life of adolescents with autism spectrum disorders: comparison to adolescents with diabetes. European Child and Adolescent Psychiatry, 21(5), 289–296.
D. Garcı´a-Villamisar et al. / Research in Autism Spectrum Disorders 7 (2013) 624–629
629
Einfeld, S. L., & Aman, M. (1995). Issues in the taxonomy of psychopathology in mental retardation. Journal of Autism and Developmental Disorder, 25, 143–167. Emerson, E., Kiernan, C., Alborz, A., Reeves, D., Mason, H., Swarbrick, R., et al. (2001). The prevalence of challenging behaviors: A total population study. Research in Developmental Disabilities, 22(1), 77–93. Garcia-Villamisar, D. A., & Dattilo, J. (2010). Effects of a leisure program on quality of life and stress of individuals with ASD. Journal of Intellectual and Disability Research, 54(7), 611–619. Gardner, W. I., Graeber-Whalen, J. L., & Ford, D. R. (2001). Self-injurious behaviors: Multimodal contextual approach to treatment. In A. Dosen & K. Day (Eds.), Treating mental illness and behavior disorders in children and adults with mental retardation (pp. 323–357). Washington, DC: American Psychiatric Press, Inc. Gerber, F., Baud, M. A., Giroud, M., & Carminati, G. G. (2008). Quality of life of adults with pervasive developmental disorders and intellectual disabilities. Journal of Autism and Developmental Disorders, 38, 1654–1665. Gerber, F., Bessero, S., Robbiani, B., Courvoisier, D. S., Baud, M. A., Traore, M. C., et al. (2011). Comparing residential programmes for adults with autism spectrum disorders and intellectual disability: Outcomes of challenging behaviour and quality of life. Journal of Intellectual Disability Research, 55(9), 918–932. Ghaziuddin, M. (2005). A family history study of Asperger syndrome. Journal of Autism and Developmental Disorders, 35(2), 177–182. Hastings, R. P. (2002). Do challenging behaviors affect staff psychological well-being? Issues of causality and mechanism. American Journal of Mental Retardation, 107(6), 555–567. Johnson, N., Frenn, M., Feetham, S., & Simpson, P. (2011). Autism spectrum disorder: parenting stress, family functioning and health-related quality of life. Families, Systems and Health, 29(3), 232–252. Kamio, Y., Inada, N., & Koyama, T. (2013). A nationwide survey on quality of life and associated factors of adults with high-functioning autism spectrum disorders. Autism, 17(1), 15–26. Kamp-Becker, I., Schroder, J., Remschmidt, H., & Bachmann, C. J. (2010). Health-related quality of life in adolescents and young adults with high functioning autism-spectrum disorder. Psycho-Social-Medicine, 7, 1–10. Kearney, D. S., & Healy, O. (2011). Investigating the relationship between challenging behavior, co-morbid psychopathology and social skills in adults with moderate to severe intellectual disabilities in Ireland. Research in Developmental Disabilities, 32(5), 1556–1563. Kober, R., & Eggleton, I. R. (2002). Factor stability of the Schalock and Keith (1993) Quality of Life Questionnaire. Mental Retardation, 40(2), 157–165. Kuhlthau, K., Orlich, F., Hall, T. A., Sikora, D., Kovacs, E. A., Delahaye, J., et al. (2010). Health-related quality of life in children with autism spectrum disorders: Results from the autism treatment network. Journal of Autism and Developmental Disorders, 40(6), 721–729. Leiter, R. G. (1980). Leiter International Performance Scale, instruction manual. Chicago: Stoelting. Mahan, S., & Kozlowski, A. M. (2011). Adults with autism spectrum disorders. In J. L. Matson & P. Sturmey (Eds.), Handbook of autism and pervasive developmental (pp. 521–539). New York: Springer International. Matson, J. L., Fodstad, J. C., & Rivet, T. T. (2009). The relationship of social skills and problem behaviors in adults with intellectual disability and autism or PDD-NOS. Research in Autism Spectrum Disorders, 3, 256–268. Matson, J. L., Gardner, W. I., Coe, D. A., & Sovner, R. (1991). A scale for evaluating emotional disorders in severely and profoundly retarded persons: Developmental of the Diagnostic Assessment for the Severely Handicapped (DASH-II). Research in Developmental Disabilities, 18, 457–469. Matson, J. L., Gonzalez, M. L., Wilkins, J., & Rivet, T. T. (2008). Reliability of the autism spectrum disorder–diagnostic for children (ASD-DC). Research in Autism Spectrum Disorders, 2(3), 533–545. Matson, J. L., Kozlowski, A. M., Worley, J. A., Shoemaker, M. E., Sipes, M., & Horovitz, M. (2011). What is the evidence for environmental causes of challenging behaviors in persons with intellectual disabilities and autism spectrum disorders? Research in Developmental Disabilities, 32(2), 693–698. Matson, J. L., Minshawi, N. F., Gonza´lez, M. L., & Mayville, S. B. (2006). The relationship of comorbid problem behaviors to social skills in persons with profound mental retardation. Behavior Modification, 30, 496–506. Matson, J. L., & Rivet, T. T. (2007). A validity study of the Autism Spectrum Disorders–Behavior Problems for Adults (ASD-BPA) scale. Journal of Developmental and Physical Disabilities, 19, 557–564. Matson, J. L., & Rivet, T. T. (2008). Reliability and factor structure of the Autism Spectrum Disorders–Behavior Problems for Adults (ASD-BPA) with intellectual disabilities. Research in Developmental Disabilities, 1, 34–47. Matson, J. L., Rivet, T. T., Fodstad, J. C., Dempsey, T., & Boisjoli, J. A. (2009). Examination of adaptive behavior differences in adults with autism spectrum disorders and intellectual disability. Research in Developmental Disabilities, 30(6), 1317–1325. Matson, J. L., & Shoemaker, M. (2009). Intellectual disability and its relationship to autism spectrum disorders. Research in Developmental Disabilities, 30(6), 1107– 1114. Matson, J. L., Wilkins, J., Boisjoli, J. A., & Smith, K. R. (2008). The validity of the autism spectrum disorders–diagnosis for intellectually disabled adults (ASD-DA). Research in Developmental Disabilities, 29, 537–546. Matson, J. L., & Turygin, N. C. (2012). How do researchers define self-injurious behavior? Research In Developmental Disabilities, 33(4), 1021–1026. Moons, P., Budts, W., & De Geest, S. (2006). Critique on the conceptualisation of quality of life: A review and evaluation of different conceptual approaches. International Journal of Nursing Studies, 43(7), 891–901. Perry, J., & Felce, D. (2002). Subjective and objective quality of life assessment: Responsiveness, response bias, and resident: Proxy concordance. Mental Retardation, 40(6), 445–456. Plimley, L. A. (2007). A review of quality of life issues and people with autism spectrum disorders. British Journal of Learning Disabilities, 35, 205–213. Preacher, K. J., & Hayes, A. F. (2008). Asymptotic and resampling strategies for assessing and comparing indirect effects in multiple mediator models. Behavior Research Methods, 40, 879–891. Rojahn, J., & Meier, L. J. (2009). Chapter nine – Epidemiology of mental illness and maladaptive behavior in intellectual disabilities. International review of research in mental retardation, 38, 239–287. Rojahn, J., & Tasse, M. J. (1996). Psychopathology in mental retardation. In J. W. Jacobson & J. A. Mulick (Eds.), Manual of diagnosis and professional practice in mental retardation. Washington, DC: American Psychological Association. Schalock, R. L., & Keith, K. D. (1993). Quality of life questionnaire manual. Ohio: IDS Publishing Corporation. Sheldrick, R. C., Neger, E. N., Shipman, D., & Perrin, E. C. (2012). Quality of life of adolescents with autism spectrum disorders: concordance among adolescents’ selfreports, parents’ reports, and parents’ proxy reports. Qual of Life Research, 21(1), 53–57. Shipman, D. L., Sheldrick, R. C., & Perrin, E. C. (2011). Quality of life in adolescents with autism spectrum disorders: Reliability and validity of self-reports. Journal of Developmental & Behavioral Pediatrics, 32(2), 85–89. Smith, K. R. M., & Matson, J. L. (2010). Behavior problems: Differences among intellectually disabled adults with co-morbid autism spectrum disorders and epilepsy. Research in Developmental Disabilities, 31(5), 1062–1069. Sturmey, P., Laud, R. B., Cooper, C. L., Matson, J. L., & Fodstad, J. C. (2010). Challenging behaviors should not be considered depressive equivalents in individuals with intellectual disabilities. II. A replication study. Research in Developmental Disabilities, 31, 1002–1007. Tenneij, N. H., Didden, R., Stolker, J. J., & Koot, H. M. (2009). Markers for aggression in inpatient treatment facilities for adults with mild to borderline intellectual disability. Research in Developmental Disabilities, 30, 1248–1254. Thorn, S. H., Bamburg, J. W., & Pittman, A. (2007). Psychosocial treatment malls for people with intellectual disabilities. Research in Developmental Disabilities, 28(5), 531–538. Totsika, V., Felce, D., Kerr, M., & Hastings, R. P. (2010). Behavior problems, psychiatric symptoms, and quality of life for older adults with intellectual disability with and without autism. Journal of Autism and Developmental Disorders, 40(10), 1171–1178. Wang, M., Schalock, R. L., Verdugo, M. A., & Jenaro, C. (2010). Examining the factor structure and hierarchical nature of the quality of life construct. American Journal on Intellectual and Developmental Disabilities, 115(3), 218–233. Wong, P. K., Wong, D. F., Schalock, R. L., & Chou, Y. C. (2011). Initial validation of the Chinese Quality of Life Questionnaire–Intellectual Disabilities (CQOL-ID): A cultural perspective. Journal of Intellectual Disability Research, 55(6), 572–580.