Autism is a disorder diagnosed in childhood that is characterized by significant impairment in social interaction, communication, and behavior patterns. Symptoms are evident by the age of three. According to the Centers for Disease Control and Prevention, current prevalence of the disorder is one in every 110 children. Although no definitive cause has been identified, it is thought that genetics, abnormal brain development and environmental risk factors play a role in the development of the disorder.
Genetics
Research conducted with twins and families suggests a strong genetic component to autism, as reported by the National Institute of Mental Health. Children whose siblings or parents have the disorder are at greater risk for developing autism themselves. At the present time, no single gene has been identified that can be linked to the disorder; it is thought that multiple genes play a role.
Brain Development
There are several areas of the brain that are thought to develop differently in children with autism, according to the National Institute for Mental Health. These include the cerebellum, brain stem, limbic system, cerebral cortex, basal ganglia and corpus callosum.
The limbic system, as described by Robert Weis in "Introduction to Child and Adolescent Psychology," plays a role in the processing of social information such as emotional reactions and social behaviors. The amygdala, one component of this system, is critical in social and emotional functioning. For children with autism, this area of the brain shows reduced activity, which may explain the lack of social understanding and interactive abilities. According to Weis, another area of the brain that plays a significant role in autism is the prefrontal cortex, which is used for processing information from the environment, attention, organizing, planning and problem solving.
Two smaller areas, the orbital and medial prefrontal cortex, are used in social interactions to understand others' thoughts and feelings. Children with autism show restricted activity in these areas of the brain. These differences in brain structure and functioning seem to explain many of the symptoms evidenced by children with autism. According to the National Institute for Mental Health, abnormal brain development is considered a leading cause in the symptoms of autism.
Environmental Risks
As reported by the National Institute for Mental Health, research has been conducted investigating the link between vaccinations and autism. The use of the preservative thimerosal in some vaccines was thought to be linked to autism. However, research conducted by Institute of Medicine found no link between the two. Exposure to other toxins including mercury, lead and other metals has been considered as a contributing factor in autism, but their role is not clear at this time.
References
- National Institute of Mental Health: Research into Causes and Treatment of Autism Spectrum Disorders
- "Introduction to Abnormal Child and Adolescent Psychology"; Robert Weis; 2008
- Centers for Disease Control and Prevention: Prevalence of Autism Spectrum Disorders
