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The Causes Of Autism: So Many Theories. So Few Answers.
Autism spectrum disorder is a neurodevelopmental disorder characterized by sometimes profound impairments in social interaction and communication skills. People with autism have difficulty reading social cues such as tone of voice and body language. They have difficulty making eye contact and often engage in repetitive movements such as rocking or twirling. The symptoms of autism comprise a spectrum of behaviors and individuals may be more or less impaired by their condition.
Autism is typically diagnosed in the first few years of life and infants and toddlers may be referred for evaluation if they have delayed language development, poor social interactiveness, or unusual and repetitive behaviors and preoccupations. Older children may merit assessment if they have difficulty making friends, sustaining conversations, engaging in imaginative interactive play or have, restricted interests or preoccupations, or rituals and routines to which they adhere strongly.(1) A definitive diagnosis is most often made by a multidisciplinary team that may include physicians, psychologists, speech therapists and others.
The number of people diagnosed with autism has increased dramatically over the last decade, and it is not clear whether this is because of improved screening and diagnosis or whether there are actually more people with autism than there used to be. The current prevalence of autism is 1-2% and there are ten times as many people currently diagnosed with autism as there were 50 years ago.(2) Recent statistics show that the prevalence of autism has increased from 4-5/10,000 in 1996 to 100 cases per 10,000 today.(3)
A Controversial Shift Back to Environmental Influences
The causes of autism remain unknown despite abundant research People with autism have been found to have abnormalities in their brains including size, structure, and neurochemical function. This suggests that the changes leading to autism occur during the earliest times of brain formation, the prenatal and earliest neonatal periods. Studies on twins and siblings with autism have pointed to an underlying genetic abnormality as the cardinal cause of autism.(4) But a recent study questioned these findings and concluded that the role of genetics has been overemphasized.(5)
The new study may help shift research away from pure genetics to the prenatal, perinatal (delivery)and neonatal (newborn) periods and the potential environmental influences during these times. Many of these possible influences have already been under investigation. Possible influences have ranged from exposures to such things such as medications and environmental toxins, to birth order and the age of parents, to the time of year of conception and birth.