The condition refers to a characteristic triad of symptoms: impairments in social interaction; impairments in communication; and restricted interests and repetitive behavior. Affected children may also manifest with other non-specific symptoms including unusual sensory perception skills and experiences, motor clumsiness (and problems with proprioception) and insomnia.
Autism is one of five developmental disorders included under the umbrella of the Pervasive Developmental Disorders. In addition to autism, other disorders in this family are Asperger’s Syndrome, Rett’s Disorder, Childhood Disintegrative Disorder. When full criteria for one of the above disorders are not met, a child may be diagnosed with Pervasive Developmental Disorder-Not Otherwise Specified (PDD-NOS).
Autism first appears during infancy or childhood, and generally, follows a steady course without remission. The condition is four times more prevalent in boys than girls in the US (Autism Society of America) and is more common than Down syndrome. The prevalence rate in India is approximately 1 in 500 or 0.20% individuals. Symptoms gradually begin after the age of six months, become established by age two or three years, and tend to continue through adulthood. Cognitive abilities in people with autism vary between those with average to above average intelligence, to borderline and mild mental retardation, and others who function within the moderate to profoundly mentally retarded range.
The exact cause of autism is not known, though the condition is thought to be associated with genetic as well as environmental factors. The immune system is thought to play an important role in autism. Children with autism have been found to have inflammation of both the peripheral and central immune systems as indicated by increased levels of pro-inflammatory cytokines. Higher prevalence of gastrointestinal immune/inflammation-mediated pathology has also been speculated to be associated with autism. The environmental causative element can be separated into pre-natal, peri-natal and post-natal factors which include maternal infections, hypoxic-ischemic birth injuries, autoimmune disease, viral infections etc. Additionally, ongoing cerebral hypoperfusion and oxidative stress have also been implicated in the etiology of autism. The mechanisms thought to be associated with autism are as follows:
An excess of neurons that causes local overconnectivity in key brain regions.
Disturbed neuronal migration during early gestation.
Unbalanced excitatory-inhibitory networks.
Abnormal formation of synapses and dendritic spines.