Thursday, April 14, 2016

Study Finds Strong Genetic Effects on Autistic Traits


Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by impairments in (a) social communication and social interaction and (b) restricted and/or repetitive behaviors or interests that varies in severity of symptoms, age of onset, and association with other disorders. ASD is both highly heritable and highly stable across age. Although improvement in symptoms is often observed between childhood and adolescence/ adulthood, longitudinal studies have found that individuals diagnosed with ASD rarely move off the spectrum and that symptom severity does not change significantly over time. Similarly, high stability has been found when autistic traits are measured in the general population.
  Research

The heritability of ASD has been established in family and twin studies. For example, twin studies in the United Kingdom, United States, Sweden, and Japan have established that the concordance rate for ASD in monozygotic (MZ) twins is much higher than in dizygotic (DZ) twins, suggesting substantial genetic influences. Likewise, twin studies of autistic traits in community and population-based samples in middle childhood and adolescence have found evidence for moderate to strong genetic effects, with the remaining variance primarily explained by non-shared environmental factors
Despite extensive research into the causal influences on autistic traits at individual ages and the finding of high stability in these traits, little is known about the overlap in genetic and environmental influences on autistic traits across age and the contribution of such influences to trait stability itself. Knowing this is important for understanding the developmental course of autistic traits and why autism behaviors appear to vary so little over time. A research study published in the Journal of the American Academy of Child & Adolescent Psychiatry investigated these questions in a general population sample of twins. More than 6,000 male and female pairs of twins were rated on a scale of autistic traits by their parents at 8, 9, and 12 years of age and by their teachers at 9 and 12 years of age. Autistic traits were assessed using the Childhood Autism Spectrum Test (CAST, formerly the Childhood Asperger Syndrome Test). The CAST was developed as a screening questionnaire for use in non-clinical settings. Data were analyzed using structural equation modeling.
                                                                                Results
The results indicated that, consistently across raters, not only were autistic traits stable and moderately to highly heritable at individual ages, but there was also a high degree of overlap in genetic influences across age. Autistic trait stability was largely accounted for by genetic factors, with the environment unique to each twin playing a minor role. The environment shared by twins had virtually no effect on the longitudinal stability in autistic traits.
                                                                             Implications
The findings of the present study have important implications for understanding ASD. They suggest that autistic traits are not only highly stable across middle childhood, but that this stability is caused largely by genetic influences in both boys and girls. This implies that stability is a biological characteristic of autistic symptoms, as opposed to being due to shared environmental factors. A caveat! The results do not mean that all variance in the stability of autistic traits is caused by genetic influences, nor do they suggest that autistic traits are fixed and resistant to change. Although the environment shared by the twins had little influence on the stability of autistic traits, the unique environment of each twin, such as being in different classes at school or receiving differential parental treatment, did appear to play a modest role in the stability of autistic traits. Despite the importance of genetics, environmental influences and treatment/intervention could still have an effect on these characteristics.
The results of this study add our knowledge of the key role that genes play in autistic traits and how these behaviors manifest themselves as children grow older. Overall, the findings suggest that the development of autistic traits in middle childhood is characterized largely by a set of stable genetic influences, but that, in addition to these influences, new genetic influences as well as modest-to-moderate environmental influences emerge at each age. Future research should include an examination of the specific nature of these causal influences on autistic traits across the lifespan. Likewise, the findings need replication in a clinical sample of individuals with ASD.
Holmboe, K., Rijsdijk, F. V., Hallett, V., Happ, F., Plomin, R., & Ronald, A. (2014). Strong genetic influences on the stability of autistic traits in childhood. J. Am. Acad. Child Adolesc. Psychiatry, 53(2), 221–230.

Monday, April 4, 2016

Autism Awareness Month - Continuing Education

More children and youth are being diagnosed with autism spectrum disorder (ASD) than ever before. Epidemiological research indicates a progressively rising prevalence trend for ASD over the past decade. Autism is much more prevalent than previously thought, especially when viewed as a spectrum condition with varying levels of symptom severity. Surveys focusing on this broader definition of autism indicate that ASD is one of the fastest growing disability categories in the world. Recent findings of the Centers for Disease Control and Prevention (CDC) Autism and Developmental Disabilities Monitoring Network ADDM (2012) indicate that 1 in every 68 school-age children has an autism spectrum disorder (ASD). The following CE courses focus on autism with the goal of contributing to autism awareness and knowledge among professionals.  
Autism Spectrum Disorder: Evidence-Based Screening and Assessment is a 3-hour online CE course that identifies DSM-5 diagnostic changes in the ASD diagnostic criteria, summarizes the empirically-based screening and assessment methodology in ASD and describes a comprehensive developmental approach for assessing children, adolescents, and young adults with ASD. Risk factors and/or early warning signs of ASD are described. Course #30-69 | 2014 | 44 pages | 40 posttest questions | 
Autism & Asperger Syndrome in Schools is a 9-hour test only CE course (book available on Amazon) that provides step-by-step guidance for screening, assessing, and educating children with ASD. Grounded in the latest research, special features include illustrative case examples, FAQs, quick reference boxes, glossary, and an index to 50 evidence-based best practice recommendations. Highly readable and comprehensive, this text is for those who want to further their understanding of the identification and treatment of school-age children with ASD. Course #101966 | 2010 | 40 posttest questions | 
Lee A. Wilkinson, PhD, CCBT, NCSP is author of the award-winning book, A Best Practice Guide to Assessment and Intervention for Autism and Asperger Syndrome in Schools, published by Jessica Kingsley Publishers. He is also editor of a recent volume in the APA School Psychology Book Series, Autism Spectrum Disorder in Children and Adolescents: Evidence-Based Assessment and Intervention in Schools and author of the new book, Overcoming Anxiety and Depression on the Autism Spectrum: A Self-Help Guide Using CBT.

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