According to new research, by the age of 8 as many as one in every 150 children in the United States develops autism or a related disorder such as Asperger's syndrome.
The study by the Centers for Disease Control and Prevention (CDC) examined cases of autism spectrum disorders (ASD) in 14 states between 2000 and 2002 in order to establish the prevalence of the disorder in the U.S.
The rigorous and comprehensive analysis has served to confirm recent estimates, which suggest the number to be at around one in 160 children.
The analysis also found that delays in diagnosis were quite common with an average of at least a year and a half from the time parents first reported odd speech problems or other social deficits, typically at around the age of 3.
For children with autism, problems arise in communicating, forming relationships and adjusting to change, and they often have unusual behaviours and interests, which can be very disabling; those with other disorders on the spectrum generally have social difficulties which are less severe, and in some cases mild.
The study suggests as many as 560,000 Americans age 21 or under struggle to cope with such disorders and the researchers say that both genetic variation and developmental factors combine to cause the disorders, but little is known about the actual cause of the disorder.
The new numbers unlikely to settle the continuing debate about whether there has been a true rise in autism and, if so, what is the underlying causes of that increase.
Dr. Julie L. Gerberding, director of the CDC says although estimates are better and more consistent, it is unclear whether there is an increase in autism spectrum disorders or whether the increase is the result of better information.
Gerberding says however, what is known is that the disorders are affecting too many children.
The researchers calculated their estimates on the basis of a detailed review of records from schools and health clinics in six states in 2000 and 2002, and from an additional eight states in 2002 alone.
The analysis involved Alabama, Arizona, Arkansas, Colorado, Georgia, Maryland, Missouri, New Jersey, North Carolina, Pennsylvania, South Carolina, Utah, West Virginia and Wisconsin.