Autism Spectrum and Neurodevelopmental Disorders

Autism spectrum disorders (ASDs) represent a heterogeneous set of neurodevelopmental disorders characterized by deficits in social communication and reciprocal interactions as well as stereotypic behaviors. The prevalence of ASDs has been increasing over the past 2 decades. According to the latest review of medical records in 14 selected sites in the United States conducted by the CDC, 1 in 88 children (1 in 54 boys and 1 in 252 girls) aged 8 years were identified as having ASDs.¹ The reason for this rise in prevalence is not fully understood, but this increase clearly shows that ASDs are a significant public health issue.

ASDs are often accompanied by significant lifelong impairments. Individuals with ASDs often require intensive parental, school, and other social support. In addition to intensive behavioral therapies, services at school ranging from individualized education plans with combinations of speech therapy, occupational therapy, social skills training and physical therapy, to individualized aides, specialized classrooms, and sometimes even specialized schools are required for most children with ASDs. While services vary by region and can be challenging to obtain for children, supports for adults are even more limited. For many adults with ASDs and significant intellectual disability, psychiatric comorbidity, and/or medical comorbidity, independence is often not achievable. Some may be able to participate in vocational training and hold basic jobs but still require assistance with daily living. Many adults live either with parents, with other family members, or in group homes or residential facilities. Most individuals with typical autism require lifelong assistance with basic living skills, as well as financial, medical, social, and psychiatric support.

In individuals with ASD and without significant intellectual disability, high-functioning autism is often diagnosed. In those without language development delays, a diagnosis of Asperger disorder is made. These individuals tend to have relatively good outcomes and are able to live independently, although challenges still exist. High-functioning individuals with normal, above-average, or even superior intelligence may be able to attend college and graduate school, but they often struggle significantly with social demands. These demands may be too challenging for many individuals with ASDs to complete higher education without substantial psychosocial supports. Similarly, high-functioning adults with ASDs may be intellectually quite capable of performing in a wide variety of jobs and pursuing careers, but navigating the unwritten social maps may be too complex and significantly limit their abilities to obtain and hold positions in the workforce. These individuals are not only at greater risk for social isolation, but they may also be at greater risk for depression and anxiety as they recognize their impairments and have enough insight to be all too aware of their differences.

As with other disorders in psychiatry, psychoeducation is critically important for patients and their families. This article aims to provide the general psychiatric community with an update on the major findings on the biology of ASDs as well as the advances in diagnostic and interventional strategies.

Update on biology of ASDs

The biology of ASDs has been investigated by state-of-the-art scientific methodologies in genetics, molecular biology, neurophysiology, neuroimaging, and neuropsychology. A consistent theme has been the heterogeneity of biological findings in the disorder. For example, to date, more than 100 disease genes and 44 genomic loci are reported in persons with ASD or autistic behavior.² It is unlikely for a single anatomic abnormality or even a single physiologic process to explain the etiology of ASDs. Rather, it is more reasonable to anticipate discoveries of risk factors that when joined in various combinations result in ASDs. Nonetheless, careful investigations focusing on individual genes and protein products, anatomical structures and neurocircuits, endophenotypes, and the environment are important in identifying such risk factors. With this in mind, we focus on 3 categories of risk factors for ASDs: genetics, brain anatomy, and environment.

Genetics. One of the largest advancements in understanding the etiology of ASDs is the identification of a variety of genetic variations, and especially copy number variants, associated with ASDs. Copy number variants are segments of DNA that have been either deleted or duplicated from a person’s genome. Thus, while genes are typically inherited in pairs (one copy from the mother and one copy from the father), persons with copy number variants that consist of a deletion will only have a single copy of a gene(s), and those with a copy number variant consisting of a duplication will actually have 3 copies of the gene(s). Both deletions and duplications have been implicated in ASDs.

Copy number variants vary in size and may include several genes or only a few. They may be inherited, or they may arise spontaneously, in which case they are referred to as “de novo” mutations. Children with ASDs have been found to have higher rates of de novo copy number variants compared with siblings without ASD diagnoses.³

TABLE 1

Selected copy number variants associated with autism spectrum disorders

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