Howlin, P., Arciuli, J., Begeer, S., Brock, J., Clarke, K., Costley, D., Di Rita, P., Falkmer, T., Glozier, N., Gray, K., Guastella, A., Horstead, S., Rice, L., Stancliffe, R., West, S., Yam, C., & Einfeld, S. (2015). Research on adults with autism – roundtable report. Journal of Intellectual and Developmental Disability, 40, 388-393.

This is an Accepted Manuscript of an article published by Taylor & Francis in Journal of Intellectual and Developmental Disability, available online: http://www.tandfonline.com/10.3109/13668250.2015.1064343

A PDF preprint can be downloaded here.

If you’d like to comment on this article (or view others’ comments), please head here.

 

The prevalence of autism spectrum disorders (ASD) in adults is estimated to be at least 1% (Brugha et al., 2011) yet almost all ASD research focuses on children. Adult intervention studies, in particular, are few in number and poor in quality (Bishop- Fitzpatrick, Minshew, & Eack, 2013) while support networks for adults with ASD are much more limited and of a far lower standard than for children (Taylor & Seltzer, 2012).

Around half of all adults are rated as having a poor or very poor outcome (Howlin & Moss, 2012), with social independence and integration remaining very limited, even when compared with other groups of individuals with disabilities (Roux et al., 2013).

It is within this context that a one-day meeting was convened at the University of Sydney, Australia, in August 2013, to discuss the current state of research on adults with ASD and to identify priorities for future research. The discussion was updated in August 2014 in light of recent publications. Participants were clinicians and/or researchers in the fields of ASD or intellectual disability, from a range of disciplines, including occupational therapy, social work, psychology (cognitive, developmental, clinical and social), child and adult psychiatry, psycholinguistics, disability research and policy, and providers of specialist services for children and adults with ASD.

The following commentary summarises the principal issues raised, identifies gaps in current knowledge and highlights potential research priorities.

Why is there a need to focus on adults with autism?

Although diagnostic and intervention services for children with ASD have improved considerably over recent decades, there is a dearth of adequate provision for adults. The lifetime costs of the disorder are considerable and are estimated to be greater than the costs of heart disease, cancer and stroke combined (Buescher, Cidav, Knapp, & Mandell, 2014). As life expectancies increase across most of the world the numbers of individuals with ASD surviving into old age will also rise significantly.

Why is there a need to focus on adults with autism?

Although many of the concerns related to growing old with ASD are common to individuals with other developmental or mental health problems, there are factors that differentiate this group from others with chronic disabilities (cf. Henninger & Taylor, 2013; Levy & Perry, 2011).

First, cognitive levels are highly variable, ranging from profound impairment to superior intelligence.

Second, with age, the severity of autistic symptomatology tends to improve, often markedly (Anderson, Liang, & Lord, 2014; Howlin, Moss, Savage, & Rutter, 2013) and a very small minority may no longer show any obvious signs of ASD in adulthood (Anderson et al., 2014; Fein et al., 2013). Thus, in general, they do not show patterns of frequent relapses or steady decline in functioning over the years (Orinstein et al., 2014); instead functional ability can improve steadily with age, although the lack of ASD-specific services for adults severely limits opportunities to develop their skills and competence levels.

Current gaps in knowledge

1. Diagnosis and assessment

Although there now exists a number of well-validated instruments available for confirming diagnosis in children with ASD (cf. Bolte & Diehl, 2013) their value with adults is less well established. While some new instruments for diagnosing ASD in adults are being developed (Eriksson, Andersen, & Bejerot, 2014; Ritvo et al., 2011) there is a lack of reliable and valid adult measures, either for confirming diagnosis or for assessing intervention outcomes.

2. Factors affecting outcome

Recent reviews (e.g. Anderson et al., 2014; Henninger & Taylor, 2013; Howlin et al., 2013; Levy & Perry, 2011; Magiati, Tay, & Howlin, 2012) document variable trajectories of adults with ASD. Even among individuals of normal IQ, outcome is highly variable: a very small minority is described as having “optimal outcomes” (Anderson et al., 2014; Fein et al., 2013; Orinstein et al., 2014), others remain severely impaired (e.g. Howlin et al., 2013).

Almost nothing is known about the factors that determine outcome. Although cognitive and communication skills clearly have some impact there is a lack of information on the role of other characteristics such as social competence, early ASD severity, personality and temperament, or physical and mental health.

The long-term impact of external factors including family stress, cultural or ethnic background, social support networks, or access to specific interventions or educational programs as children is also unknown. Claims that early intensive interventions can result in savings of many millions of dollars over subsequent decades (e.g. Chasson, Harris, & Neely, 2007) are unsupported by any direct evidence and although there is some evidence that access to behavioural interventions may be helpful, Orinstein et al. (2014) found no association between long-term outcome and intensity of early intervention.

Similarly, although there is a growing emphasis on the importance of helping children with ASD succeed in integrated school settings, the long-term impact of specific educational programs, especially in secondary schools and in tertiary education, remains largely unexplored

3. Effectiveness of adult-based interventions

Recent systematic reviews highlight both the small numbers and low quality of most adult intervention studies (Lounds Taylor et al., 2012; National Institute for Health and Care Excellence (NICE), 2013). The UK NICE clinical guidelines were unable to recommend any specific type of treatment, although programmes based on behavioural principles were rated positively and certain interventions, such as social skills or leisure programmes were also considered to show benefits.

Specialist, supported employment schemes, too, appear to be beneficial (Mavranezouli et al., 2013). However, adults with ASD are usually accommodated within generic services for individuals with intellectual disabilities. These services are rarely able to take into account ASD-specific requirements and there are no data on the cost effectiveness of the various interventions, support programmes, residential or day provision currently provided to adults with ASD.

4. Co-occurring problems in adulthood

a) Mental health problems – identification, causes and treatment.

Accurate estimates of psychiatric difficulties among adults with ASD are compromised by the lack of validated measures to identify mental health problems in this group. People with ASD may interpret questionnaire items in a very different way from other individuals. Their capacity to report on personal mood states is also likely to be impaired as a consequence of difficulties in self-awareness (Williams, 2010).

Although figures for rates of mental health problem in this group vary widely (from 20% to >75% (Joshi et al., 2013; Mannion, Brahm, & Leader, 2014; Mazzone, Ruta, & Reale, 2012); data on the types of mental health problems experienced are more consistent, with difficulties related to anxiety, depression and obsessions/compulsions being frequently reported.

Diagnoses of schizophrenia and bipolar disorder are much less frequent. Although some reports suggest that suicide rates are high, there are no reliable data on incidence.

There are some indications that factors related to social isolation or loss (e.g., lack of work and/or leisure activities; problems in leaving home; coping with the demands of college or further education; difficulties in finding and maintaining work; loss of family members; changes in care or support staff, etc.) may influence the onset of mental health problems (e.g. Hutton, Goode, Murphy, Le Couteur, & Rutter, 2008) but there are currently no systematic data that address this issue.

The lack of evidence-based treatments in this group is a further problem. Pharmacological or psychological interventions commonly used with individuals with mental health problems have not been trialled with adults with ASD (National Institute for Health and Care Excellence (NICE), 2012).

Although there are some positive reports on the effectiveness of CBT for children and adolescents with ASD (see Ho, Stephenson, & Carter, 2014) these interventions have not been tested on adults.

Finally, anecdotal evidence suggests that many adults with ASD and mental health problems have difficulty accessing mental health services. This may be a consequence of these services being provided by professionals with limited knowledge of ASD (Underwood, McCarthy, & Tsakanikos, 2010).

b) Forensic problems

Despite suggestions in the media and occasionally in the scientific literature, that individuals with ASD are more likely to commit serious crimes (Scragg & Shah, 1994) rates of offending among individuals with ASD are actually less than in the general population (Ghaziuddin, 2013; King & Murphy, 2014). However, if problems with the criminal justice system do arise, these can be very difficult to deal with.

There is little knowledge about the needs or difficulties of individuals with ASD among those working in the criminal justice system (including judges, prison psychiatrists, wardens, etc.). Crucially, too, in-prison treatments that rely on group interaction, social understanding and empathy are not designed for people with ASD.

c) Physical illness

Little is known about the physical health of adults with ASD. Although high rates of chronic gastro-intestinal problems are reported in children (Mazurek et al., 2013) the long-term effects of these or other difficulties is almost entirely unresearched.

There are some indications (albeit from small samples) that mortality rates are significantly higher than in the general population, with the most common causes of death being respiratory failure, heart problems and seizures (Bilder et al., 2013).

The presence of epilepsy is also associated with cognitive decline in adulthood and higher rates of behavioural problems (Howlin, Savage, Moss, Tempier, & Rutter, 2014).

d) Other developmental disorders

Rates of ASD are significantly elevated amongst individuals with other genetic or developmental disorders (Zafeiriou, Ververi, Dafoulis, Kalyva, & Vargiami, 2013). Here, too, almost nothing is known about the trajectories into adulthood, or response to intervention among individuals with both ASD and another specific disorder (e.g., fragile X syndrome, foetal alcohol syndrome disorders, etc.).

5. Older adults

Demographically, it is evident that the numbers of elderly people with ASD will increase significantly over the next few decades. However, among descriptive studies of adult cohorts, the average age tends to be around 30 years and we know almost nothing about the ageing process in older individuals.

Although the available evidence suggests that the low quality of life in autism persists in elderly individuals (van Heijst & Geurts, 2014) we do not know whether this group is more, or less or prone to cognitive decline than others or which areas of skill remain intact and which are more likely to show decline.

At present many older individuals with ASD, who do not have severe intellectual disability or severely challenging behaviours, remain at home supported largely by their aging parents (Howlin et al., 2013). What will happen when this “invisible” network of carers is no longer available is a source of great anxiety to both older adults with ASD and their parents.

There is no research into models of care that are appropriate for older adults with ASD; no information on how current services (already increasingly overstretched) for the elderly will be able to cope with individuals with special needs.

6. ASD in subgroups

a) Minority groups

Two recent reviews of interventions for children with ASD or other neurodevelopmental disabilities (Kasari & Patterson, 2012; Norbury & Sparks, 2013) highlight the many biases in such studies, particularly biases of language, cultural background and socioeconomic status. These concerns apply equally to adult studies.

b) Females

Remarkably little is known about ASD in females (Kirkovski, Enticott, & Fitzgerald, 2013). Although the ratio of males to females diagnosed with ASD is typically around 4 to 1 (Frazier, Georgiades, Bishop, & Hardan, 2014) there are suggestions that females may be diagnosed later (Begeer et al., 2013) or underdiagnosed because of their relatively superior social and communication skills (Dworzynski, Ronald, Bolton, & Happé, 2012; Zwaigenbaum et al., 2012). Thus, diagnostic systems for adult females may be even less satisfactory than for adult males.

Some research also indicates that social outcomes for females tend to be less positive overall than for males (e.g. Howlin et al., 2013). Response to treatment may also differ. However, these conclusions remain uncertain because of the very small numbers of women included in most studies.

c) Individuals with “savant skills”

Among individuals with ASD of all levels of cognitive ability there exist some with specific islets of ability that are far superior to those found in the general population (memory, music, computing ability tend to be most commonly identified). However, few individuals prove able to use these skills in ways that promote social inclusion or higher employment levels (Howlin, Goode, Hutton, & Rutter, 2009).

Conversely, the world of work has little capacity to identify and make use of these skills. How these gifts could be developed to result in greater personal, practical and economic benefits is yet another area that warrants further research.

Public policy issues

There has been little development of public policy regarding service delivery for adults with ASD.

In Australia, the government introduced the Helping Children with Autism package in 2007 but this is explicitly restricted to those under 13 years of age (Australian Government Department of Social Services, 2014). More recently, Australia has launched a National Disability Insurance Scheme and international experience has documented a number of challenges in successfully implementing such schemes for adults with mental disorders in general, including ASD (Salvador-Carulla & Einfeld, 2014).

In the USA, the Combating Autism Act was passed in 2006 (The White House, 2006). The Act provides substantial funding for biomedical research, surveillance and early intervention, but no specific provisions for adults.

In contrast, the UK Autism Act 2009, (The National Autistic Society, 2013) explicitly requires development of an adult autism strategy to support the needs of adults with autism. As far as we are aware, the UK is unique in passing such legislation although, unfortunately, there is no additional funding provided to ensure that the recommendations are adequately fulfilled.

Recent Initiatives

For the vast majority of individuals with ASD the services necessary to support them through adulthood are unavailable or inadequate. There has been little research so far to indicate the most cost-effective strategies to guide service provision.

However, increasing recognition of this problem has led to a number of recent initiatives. These include the Autism-in-Older Adults Working Group in North Carolina (Piven, Rabins, & Autism-in-Older Adults Working Group, 2011), the Ontario Working Group on Mental Health & Adults with Autism Spectrum Disorder (Ontario Working Group on Mental Health & Adults with ASD, 2014), the collaboration between AGE Platform Europe and Autism-Europe (Autism Europe, 2012) and the adult stream of the Australian Collaborative Research Centre on Living with Autism Spectrum Disorder.

It is to be hoped that the establishment of evidence-based interventions will be the product of these much-needed endeavours.

Conclusion

Gaps abound in research, policy and service delivery in relation to adults with ASD. The very limited available information indicates that far too many individuals experience poor outcomes during adult life. This situation is unacceptable for individuals, distressing for families, and a lost opportunity for a positive contribution to society.

Researchers must generate the knowledge to enable effective, evidence-informed policies and services to be developed. The way forward involves action on multiple fronts: the development of better diagnostic and assessment methods for adults; research on trajectories throughout adulthood, including longitudinal studies, factors that affect adult trajectories, and the long-term effects of interventions in childhood; systematic study of identification, causes and treatment of co-occurring problems during adulthood; and a focus on issues related to subgroups of adults with ASD.

Recent collaborations formed to address this issue offer reason to be optimistic the challenge can be met.

References

Anderson, D. K., Liang, J. W., & Lord, C. (2014). Predicting young adult outcome among more and less cognitively able individuals with autism spectrum disorders. Journal of Child Psychology and Psychiatry, 55(5), 485-494. doi: 10.1111/jcpp.12178

Australian Government Department of Social Services. (2014). Helping Chiidren with Autism. Retrieved August, 2014, from http://www.dss.gov.au/our- responsibilities/disability-and-carers/program-services/for-people-with- disability/helping-children-with-autism

Autism Europe. (2012). Towards a better quality of life: The rights of ageing people with autism. Belgium: Autism-Europe a.i.s.b.l.

Begeer, S., Mandell, D., Wijnker-Holmes, B., Venderbosch, S., Rem, D., Stekelenburg, F., & Koot, H. M. (2013). Sex differences in the timing of identification among children and adults with autism spectrum disorders. Journal of autism and developmental disorders, 43(5), 1151-1156. doi: 10.1007/s10803-012-1656-z

Bilder, D., Botts, E. L., Smith, K. R., Pimentel, R., Farley, M., Viskochil, J., . . . Coon, H. (2013). Excess mortality and causes of death in autism spectrum disorders: a follow up of the 1980s Utah/UCLA autism epidemiologic study. Journal of autism and developmental disorders, 43(5), 1196-1204. doi: 10.1007/s10803-012-1664- z

Bishop-Fitzpatrick, L., Minshew, N. J., & Eack, S. M. (2013). A systematic review of psychosocial interventions for adults with autism spectrum disorders. Journal of Autism and Developmental Disorders, 43(3), 687-694. doi: 10.1007/s10803-012- 1615-8

Bolte, E. E., & Diehl, J. J. (2013). Measurement tools and target symptoms/skills used to assess treatment response for individuals with autism spectrum disorder. Journal of autism and developmental disorders, 43(11), 2491-2501. doi: 10.1007/s10803-013-1798-7

Brugha, T. S., McManus, S., Bankart, J., Scott, F., Purdon, S., Smith, J., . . . Meltzer, H. (2011). Epidemiology of autism spectrum disorders in adults in the community in England. Archives of General Psychiatry, 68(5), 459-465. doi: 10.1001/archgenpsychiatry.2011.38

Buescher, A.V.S., Cidav, Z., Knapp, M., & Mandell, D.S. (2014). Costs of Autism Spectrum Disorders in the United Kingdom and the United States. JAMA Pediatrics, 168(8), 721-728. doi: doi:10.1001/jamapediatrics.2014.210

Chasson, G. S., Harris, G. E., & Neely, W. J. (2007). Cost Comparison of Early Intensive Behavioral Intervention and Special Education for Children with Autism. Journal of Child and Family Studies, 16(3), 401-413. doi: 10.1007/s10826-006-9094-1

Dworzynski, K., Ronald, A., Bolton, P., & Happé, F. (2012). How Different Are Girls and Boys Above and Below the Diagnostic Threshold for Autism Spectrum Disorders? Journal of the American Academy of Child & Adolescent Psychiatry, 51(8), 788 – 797. doi: 10.1016/j.jaac.2012.05.018

Eriksson, J. M., Andersen, L. M. J., & Bejerot, S. (2014). Assessing Adults with Normal Intelligence for ASD. In V. B. Patel, V. R. Preedy & C. R. Martin (Eds.), Comprehensive Guide to Autism (pp. 369-385). New York: Springer.

Fein, D., Barton, M., Eigsti, I.M., Kelley, E., Naigles, L., Schultz, R.T., . . . Tyson, K. (2013). Optimal outcome in individuals with a history of autism. Journal of Child Psychology and Psychiatry, 54(2), 195-205. doi: 10.1111/jcpp.12037

Frazier, T.W., Georgiades, S., Bishop, S.L., & Hardan, A.Y. (2014). Behavioral and cognitive characteristics of females and males with autism in the Simons Simplex Collection. Journal of the American Academy of Child and Adolescent Psychiatry, 53(3), 329-340. doi: 10.1016/j.jaac.2013.12.004

Ghaziuddin, M. (2013). Violent behavior in autism spectrum disorder: Is it a fact, or fiction? Current Psychiatry, 12(10), 23-32.

Henninger, N. A., & Taylor, J. L. (2013). Outcomes in adults with autism spectrum disorders: a historical perspective. Autism, 17(1), 103-116. doi: 10.1177/1362361312441266

Ho, B.P.V., Stephenson, J., & Carter, M. (2014). Cognitive-Behavioral Approach for Children with Autism Spectrum Disorders: a Meta-Analysis. Review Journal of Autism and Developmental Disorders, 1, 18-33. doi: 10.1007/s40489-013-0002-5

Howlin, P., Goode, S., Hutton, J., & Rutter, M. (2009). Savant skills in autism: psychometric approaches and parental reports. Philosophical Transactions of the Royal Society B: Biological Sciences, 364(1522), 1359-1367. doi: 10.1098/rstb.2008.0328

Howlin, P., & Moss, P. (2012). Adults with autism spectrum disorders. The Canadian Journal of Psychiatry, 57(5), 275-283.

Howlin, P., Moss, P., Savage, S., & Rutter, M. (2013). Social outcomes in mid- to later adulthood among individuals diagnosed with autism and average nonverbal IQ as children. Journal of the American Academy of Child & Adolescent Psychiatry, 52(6), 572-581 e571. doi: 10.1016/j.jaac.2013.02.017

Howlin, P., Savage, S., Moss, P., Tempier, A., & Rutter, M. (2014). Cognitive and language skills in adults with autism: a 40-year follow-up. Journal of Child Psychology and Psychiatry, 55(1), 49-58. doi: 10.1111/jcpp.12115

Hutton, J., Goode, S., Murphy, M., Le Couteur, A., & Rutter, M. (2008). New-onset psychiatric disorders in individuals with autism. Autism, 12(4), 373-390. doi: 10.1177/1362361308091650

Joshi, G., Wozniak, J., Petty, C., Martelon, M. C., Fried, R., Bolfek, A., & Biederman, J. (2013). Psychiatric Comorbidity and functioning in a clinically referred population of adults with autism spectrum disorders: a comparative study. Journal of Autism and Developmental Disorders, 43(6), 1314-1325. doi: 10.1007/s10803-012-1679-5

Kasari, C., & Patterson, S. (2012). Interventions addressing social impairment in autism. Current Psychiatry Reports, 14(6), 713-725. doi: 10.1007/s11920-012-0317-4

King, C, & Murphy, G. (2014). A systematic review of people with autism spectrum disorder and the criminal justice system. Journal of Autism and Developmental Disorders, 44(11), 2717-2733. doi: 10.1007/s10803-014-2046-5

Kirkovski, M., Enticott, P. G., & Fitzgerald, P. B. (2013). A review of the role of female gender in autism spectrum disorders. Journal of Autism and Developmental Disorders, 43(11), 2584-2603. doi: 10.1007/s10803-013-1811-1

Levy, A., & Perry, A. (2011). Outcomes in adolescents and adults with autism: A review of the literature. Research in Autism Spectrum Disorders, 5(4), 1271-1282. doi: DOI 10.1016/j.rasd.2011.01.023

Lounds Taylor, J. , Dove, D., Veenstra-VanderWeele, J., Sathe, N.A., McPheeters, M.L., Jerome, R.N., & Warren, Z. . (2012). Interventions for Adolescents and Young Adults With Autism Spectrum Disorders. Comparative Effectiveness Review No. 65. Rockville, MD: Agency for Healthcare Research and Quality.

Magiati, I., Tay, X. W., & Howlin, P. (2012). Early comprehensive interventions for children with Autism Spectrum Disorders: a critical synthesis of recent review findings. Neuropsychiatry, 2(6), 543-570.

Mannion, A., Brahm, M., & Leader, G. (2014). Comorbid psychopathology in autism spectrum disorder. Review Journal of Autism and Developmental Disorders, 1, 124-134. doi: 10.1007/s40489-014-0012-y

Mavranezouli, I., Megnin-Viggars, O., Cheema, N., Howlin, P., Baron-Cohen, S., & Pilling, S. (2013). The cost-effectiveness of supported employment for adults with autism in the United Kingdom. Autism. doi: 10.1177/1362361313505720

Mazurek, M. O., Vasa, R. A., Kalb, L. G., Kanne, S. M., Rosenberg, D., Keefer, A., . . . Lowery, L. A. (2013). Anxiety, sensory over-responsivity, and gastrointestinal problems in children with autism spectrum disorders. Journal of Abnormal Child Psychology, 41(1), 165-176. doi: 10.1007/s10802-012-9668-x

Mazzone, L., Ruta, L., & Reale, L. (2012). Psychiatric comorbidities in Asperger syndrome and high functioning autism: diagnostic challenges. Annals of General Psychiatry, 11(1), 16. doi: 10.1186/1744-859X-11-16

National Institute for Health and Care Excellence (NICE). (2012). Autism: Recognition, referral, diagnosis and management of adults on the autism spectrum. London: National Institute for Health and Care Excellence.

National Institute for Health and Care Excellence (NICE). (2013). Autism: The management and support of children and young people on the autism spectrum London: National Institute for Health and Care Excellence.

Norbury, C. F., & Sparks, A. (2013). Difference or disorder? Cultural issues in understanding neurodevelopmental disorders. Developmental Psychology, 49(1), 45-58. doi: 10.1037/a0027446

Ontario Working Group on Mental Health & Adults with ASD. (2014). Ontario Working Group on Mental Health & Adults with ASD. Retrieved August, 2014, from http://www.adultasd.ca/

Orinstein, A. J., Helt, M. , Troyb, E., Tyson, K. E., Barton, M. L., Eigsti, I. M., . . . Fein, D. A. (2014). Intervention for optimal outcome in children and adolescents with a history of autism. Journal of Developmental & Behavioral Pediatrics, 35(4), 247- 256. doi: 10.1097/DBP.0000000000000037

Piven, J., Rabins, P., & Autism-in-Older Adults Working Group. (2011). Autism spectrum disorders in older adults: toward defining a research agenda. Journal of the American Geriatric Society, 59(11), 2151-2155. doi: 10.1111/j.1532- 5415.2011.03632.x

Ritvo, R. A., Ritvo, E. R., Guthrie, D., Ritvo, M. J., Hufnagel, D. H., McMahon, W., . . . Eloff, J. (2011). The Ritvo Autism Asperger Diagnostic Scale-Revised (RAADS-R): a scale to assist the diagnosis of Autism Spectrum Disorder in adults: an international validation study. Journal of Autism and Developmental Disorders, 41(8), 1076- 1089. doi: 10.1007/s10803-010-1133-5

Roux, A. M., Shattuck, P. T., Cooper, B. P., Anderson, K. A., Wagner, M., & Narendorf, S. C. (2013). Postsecondary employment experiences among young adults with an autism spectrum disorder. Journal of the American Academy of Child & Adolescent Psychiatry, 52(9), 931-939. doi: 10.1016/j.jaac.2013.05.019

Salvador-Carulla, L., & Einfeld, S. (2014). Mental illness and the National Disability Insurance Scheme: Lessons from Europe. Australian & New Zealand Journal of Psychiatry, 48(5), 482-484. doi: 10.1177/0004867414531833

Scragg, P. , & Shah, A. (1994). Prevalence of Asperger’s syndrome in a secure hospital. The British Journal of Psychiatry, 165, 679-982.

Taylor, J. L., & Seltzer, M. M. (2012). Developing a vocational index for adults with autism spectrum disorders. Journal of Autism and Developmental Disorders, 42(12), 2669-2679. doi: 10.1007/s10803-012-1524-x

The National Autistic Society. (2013). Autism Act 2009. Retrieved August, 2014, from http://www.autism.org.uk/autismact

The White House. (2006). Fact Sheet: Combating Autism Act of 2006. Retrieved August, 2014, from http://georgewbush-whitehouse.archives.gov/news/releases/2006/12/20061219-3.html

Underwood, L., McCarthy, J., & Tsakanikos, E. (2010). Mental health of adults with autism spectrum disorders and intellectual disability. Current opinion in psychiatry, 23(5), 421-426. doi: 10.1097/YCO.0b013e32833cfc18

van Heijst, B.F., & Geurts, H.M. (2014). Quality of life in autism across the lifespan: A meta-analysis. Autism, Advance online publication. doi: 10.1177/1362361313517053

Williams, D. (2010). Theory of own mind in autism: Evidence of a specific deficit in self- awareness? Autism, 14(5), 474-494. doi: 10.1177/1362361310366314

Zafeiriou, D. I., Ververi, A., Dafoulis, V., Kalyva, E., & Vargiami, E. (2013). Autism spectrum disorders: the quest for genetic syndromes. American Journal of Medical Genetics Part B: Neuropsychiatric Genetics, 162B(4), 327-366. doi: 10.1002/ajmg.b.32152

Zwaigenbaum, L., Bryson, S. E., Szatmari, P., Brian, J., Smith, I. M., Roberts, W., . . . Roncadin, C. (2012). Sex differences in children with autism spectrum disorder identified within a high-risk infant cohort. Journal of Autism and Developmental Disorders, 42(12), 2585-2596. doi: 10.1007/s10803-012-1515-y