The number of children with autism is on the rise in Australia, but a lack of data is driving up the risk of the disorder affecting them in the future.
The first study to look at the long-term outcomes of people with autism was released this week, with a similar report coming out next month.
The new study is from the Centre for Disease Control and Prevention and uses data from the Autism Risk Behaviour Surveillance System.
This data is available online in the journal Paediatrics and Child Health.
The researchers looked at the autism risk in children born between the years 1993 and 2014, and also compared children born in the same period in 2015 to those born in 1994.
They found that the number of people diagnosed with autism in the last two years of life rose from 6.7 per cent to 7.5 per cent, with the highest rates among children born during the years of the Great Depression and World War II.
The authors also found that those diagnosed with the disorder had higher rates of mental health issues in childhood and were more likely to suffer from a range of disorders in later life.
The risk of developing autism increased with age, with an increased risk seen in people aged 15 to 29 years.
The report also found an increased rate of autism in children who had been vaccinated for the Hepatitis A vaccine.
The rate of death from childhood infections also increased, with people diagnosed as having been exposed to a range that includes measles, mumps, rubella, and HIV.
The study also found a significant increase in the number and type of chronic conditions seen in children with a diagnosis of autism.
This was found in areas of higher risk, such as children diagnosed with asthma, depression, bipolar disorder, and autism.
The number and types of chronic disorders seen in autism increased the more severe the condition.
The findings were published in the Journal of Autism and Developmental Disorders.
The study also revealed an increase in autism-related conditions in children diagnosed between 1994 and 2011.
The most common conditions found to be linked to autism were attention deficit hyperactivity disorder (ADHD), dyslexia, and developmental delays.
According to the Centers for Disease Controls and Prevention, about 8.5 million Australians have autism spectrum disorders, a condition that includes difficulty paying attention and social behaviour.
The Australian Autistic Society said the findings show the need for a national approach to autism screening, with more people being assessed and more people having their risk profiles reviewed.
“The findings suggest that screening for autism is more effective at protecting the population from an increased number of adverse events than the standard autism screening program that has been shown to be highly effective in the United States,” said Paul McManus, the chief executive of the Australian Autistics Society.
Aboriginal children also appear to be at higher risk of autism, with almost 40 per cent of them diagnosed with it.
The AAP says this has to be taken into account when deciding when and how to start early intervention.
It is recommended that the age of onset of autism should be set at around the age that children start school, but that a child can still have a low risk if they start school early.
Australia has one of the highest levels of autism rates in the world, with over one in five Australians being diagnosed with a disability.
The National Autistic Social Network says it is important to have a national autism screening strategy and that children should be diagnosed early to avoid a lifetime of difficulties.
With the number one reason for being diagnosed as an autistic child now decreasing, the number who are still being diagnosed could be in jeopardy.
ABC News’ Jessica Martin reports.