COVER STORY: Why so many people with autism never make it to their 40th birthday.

Elizabeth* has a six-year-old daughter with autism, who she describes as “extraordinary, bright, inquisitive, sensitive, kind, fiery and impulsive”. Sarah* was diagnosed when she was five, but even before that, her mum started noticing a common theme in her emotional responses: distress.

“My daughter was three years old when I began to see that she was suffering from anxiety,” Elizabeth tells Mamamia. “Her responses were often extreme to certain situations.”

Now, as a primary school student, “She is, more often than not, quite stressed and extremely heightened.”

Early intervention, however, including “a combination of medication and professional treatment,” has vastly improved Sarah’s quality of life. She hasn’t been bullied at school, she’s able to make and retain friendships, and she’s been taught how to remove herself from a situation when she starts to feel overwhelmed.

But many other children with autism don’t receive this kind of support, and even with the resources and strategies available to Sarah, who is described as ‘high-functioning’ on the autism spectrum, she’ll likely face struggles in her life that people without autism just don’t have to.

So what happens when children like Sarah grow up? Or her peers, many of whom are lower functioning, and may also have cognitive disabilities?

For a long time, it wasn’t clear. The relevant research didn’t exist. Then a study from Sweden, published in 2016, identified “shameful” rates of premature death among those with autism.

The study found that people with autism die an average of 16 years earlier than members of the general population, and for those who also had learning difficulties, their life expectancy was 30 years shorter than people without autism.

In the wake of the research, John Spiers, the Chief Executive of UK charity Autistica, said: “We cannot accept a situation where many autistic people will never see their 40th birthday.”

A US study published the following year found people diagnosed with autism die at an average age of just 36.

While the same research hasn’t been replicated in Australia, Braedan Hogan, Acting Chief Executive Officer at Amaze – the peak body for people on the autism spectrum in Victoria – says, “I wouldn’t be surprised if [our trends] were very similar”.

Hogan says the life expectancy statistic is one that is well-known in the autism advocacy community.

So why do so many people with autism never make it to their 40th birthday? What is causing this early mortality?

While the reasons are varied, some are hauntingly specific.

One cause of death identified in the US study was preventable injury - with people with autism three times more likely than the general population to die from injuries. Specifically, drowning is the most common fatal injury in children with autism, with their risk peaking between the ages of five and seven.

Dr. Guohua Li, the senior author of the study, told CNN children with autism are often anxious, and wandering is one way they deal with their anxiety. To calm themselves, many instinctively wander towards water.

Teaching water safety to children with autism, therefore, is crucial.

Another disturbing contributor to the mortality rate in people with autism, identified in the Swedish study published in the British Journal of Psychiatry, is suicide.

The researchers found that those diagnosed with autism, who didn't have a cognitive disability, were nine times more likely to die by suicide than the general population. These numbers were the highest for females, and for higher functioning people on the autism spectrum.

Experts believe these people are particularly at risk, because they're aware of their condition and the constraints they have.

For Elizabeth, this statistic struck a chord. "Sarah's awareness is such that as she gets older, she will be able to identify certain differences between her and her peers," she says. As a result, Elizabeth isn't surprised by the suicide rates in this group.

"Anxiety is a battle my daughter faces daily," she says. "She is on an anti depressant that is also able to reduce her anxiety to a manageable level.  She is on melatonin to sleep through the night.

Listen to: Everything you need to know if your child's being bullied. (Post continues after audio.)

"We are only where we are at because we've had a lot of help.  And I will continue seek out whatever help she needs to improve her quality of life.  Her mental health is something I always monitor."

Bullying and social isolation is also thought to contribute to mental health difficulties in people with autism.

According to Hogan, over half of people with autism in Australia say they feel socially isolated, and less than four per cent think the wider community is willing to support them.

"This lack of understanding and support for autistic people in the community generally leads to autistic people withdrawing from the community, becoming socially isolated, not being connected into family, friends, employment, education," he says. "I think that lack of social and community engagement really does contribute to the poorer outcomes we see across the board in statistics for autistic people."

A third reason for the low life expectancy in people with autism is their likelihood of developing a variety of medical problems, such as gastrointestinal disorders. It's their increased risk of heart disease, however, that's particularly dangerous.

While researchers don't know for sure why heart disease is so common in people with autism, a report by Autistica suggests it's likely down to stress.

Issues such as sensory overload, sensitivity to noise and bright lights, as well as the constant burden of social interactions mean those with autism can be in a perpetual state of fight or flight.

It's a reality Elizabeth recognises in her daughter, and Amaze's Braedan Hogan says is a crucial challenge to acknowledge for people with autism.

Watch: Author Kathy Lette on why we should change the way we view autism.

As a result of these findings, Amaze launched a campaign 'Do One Thing For Autism,' encouraging those in the wider community to find out what people with autism would like others to be aware of, and committing to performing simple acts to help.

"That can be as simple as, if you see someone in your workplace that's having issues, and you know that you need to change the schedule, give them appropriate notice in advance," Hogan says. "If you know that your child goes to school with an autistic child, and you're going to ask them over for a party, ask the parents how they are with loud noises, or you might need to change some things to make sure they're included.

"I hear constantly autistic people don't want to go into public toilets because there might be hand dryers going off. I mean, where's the dignity in having to ask somebody to go in advance, and ask somebody not to use the hand dryer so they can go into the toilets?

"We see a lot about building and ramps and rails for people with physical disability, what we don't see is how the sensory environment can impact on autistic people."

For both Elizabeth and Hogan, the knowledge that many people with autism won't make it to their 40th birthday isn't unnecessarily alarmist, but instead highlights the impact autism can have on an individual's mental and physical health.

"While it makes you sit upright when you hear it, I think it really speaks to the fact that more action really does need to be taken," Hogan says.

"I think it's really important for people to know."

*Name have been changed to protect anonymity. 

For support and information about autism, you can the Autism Advisory and Support Service (AASS) 24 hour Autism Hotline on 1300 222 777. You can also find more information about resources and support at Amaze.org.au. 

If you’re suffering from depression or anxiety and need help, or just someone to chat to, you can call Lifeline on 13 11 14 or BeyondBlue on 1300 22 4636.