She says psychiatrists need to have sufficient training to be able to differentiate it from other conditions.
"Autism is not a mental illness but people with autism are at very high risk of getting a mental illness," Dr Franklin told AAP.
"The message is psychiatrists need to learn more about autism in order to be able to diagnose and manage the mental health problems that people have."
The research shows about 50 per cent of autistic adults suffer from anxiety, while 40 per cent depression.
"Of particular concern is research evidence indicating that adults on the autism spectrum are seven times more likely to die from suicide than those in the general population," Dr Franklin said.
As more children get diagnosed with autism spectrum disorder, in part due to better identification, adults are increasingly starting to recognise they might have autism.
University of Otago psychiatrist Dr David Bathgate says a new training program for psychiatrists is required so they can accurately manage autism spectrum disorder.
"There is still a large gap between recommendations for best mental healthcare in autism and the reality of overstretched clinical service providers," Dr Bathgate told the Royal Australian and New Zealand College of Psychiatrists (RANZCP) annual congress in Auckland.
"There is an urgent need for more training of psychiatrists on the diagnosis and management of autism spectrum disorder and the mental illnesses that complicate the condition."
RANZCP president Dr Kym Jenkins has acknowledged the general guidelines for managing autistic adults may need "strengthening".
Readers seeking support and information about suicide prevention can contact Lifeline on 13 11 14.
Suicide Call Back Service 1300 659 467.