More than 100 prominent academics have signed an open letter to Prime Minister Malcolm Turnbull calling for a royal commission into violence, abuse and neglect of people with a disability.

Key points: Experts say psychotropic drugs being over prescribed to control behaviour

Experts say psychotropic drugs being over prescribed to control behaviour One man with a disability nearly died, developed gangrene gallbladder after 'drug-induced toxicity'

One man with a disability nearly died, developed gangrene gallbladder after 'drug-induced toxicity' His case is one of many examples of group home mistreatment documented by the ABC

The ABC has documented numerous cases of abuse and mistreatment of disabled people, particularly in group homes, and the open letter expresses dismay that the Federal Government chose not to proceed with an earlier recommendation for a royal commission.

Doctors and professors from around the country have called on Mr Turnbull to establish a royal commission with "substantial investigative powers, including the capacity to compel witnesses from within service organisations; inspectorate powers to visit institutional environments which facilitate violence, abuse and neglect; and the ability to refer criminal matters to the police".

'Drug-induced toxicity' blamed for near-death

In one disturbing case of mistreatment, the ABC has been told psychotropic drugs are potentially being over-prescribed in order to control the behaviour of disabled people in group homes.

Ros Phillips told Lateline her son Jason Coulstock spent 16 years "of hell" in a group home but the final straw came when he was hospitalised in January in agony.

During his time in hospital, Jason, 40, had to be revived three times. Doctors diagnosed a gangrene gallbladder and eventually his gallbladder was removed.

As Ms Phillips sat by her son's bed in intensive care, she went through his medication pack and made a startling discovery.

Jason Coulstock's Webster pack contained medications his carers didn't know were prescribed. ( ABC News )

"It was full of medication that I'd never seen," she said.

"[The hospital doctors] came back and they said to me Jason was suffering from drug-induced toxicity.

"That was why they believe he had gangrene gallbladder because the liver wasn't able to function and process all the medication he was taking."

A specialist psychiatrist found his daily medication pack included four anti-psychotic medications, an anti-depressant and a beta-blocker, in addition to the medication Jason used long-term.

They are all psychotropic medications that can be used, sometimes outside prescribing guidelines, to control behaviour.

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'Trying to shut him up'

Jason Coulstock sustained a black eye while living in a NSW group home. ( Supplied )

In the 12 months leading up to his hospitalisation, Jason's behaviour had been deteriorating and he had been lashing out in the group home he lived in in the New South Wales southern highlands.

Ms Phillips said instead of trying to fix the situation to improve his behaviour, Jason was medicated.

"They were trying to shut him up keep him quiet," she said.

"I was so angry."

The NSW Government, which runs the home, said all changes to Jason's medications were determined by medical professionals and Ms Phillips had consented to each medication change, something she rejects.

"FaCS [Family and Community Services] finds claims that its staff breached restricted practices to be inconsistent with the records held by the ADHC [Ageing, Disability and Home Care] group home," the Government stated.

The GP clinic where Jason was treated told the ABC in a statement the medication changes were led by Jason's psychiatrist and approved by Ms Phillips.

"Lines of communication with his disability carers and mother were kept open throughout the time he received care," it stated.

But the ABC has a letter from Jason's psychiatrist indicating that he did not know about at least two of the medications.

Jason Coulstock recovering in hospital after losing his gallbladder. ( ABC News )

Use of 'chemical restraints' restricted

Kylee Roberts, a facilitator with the New South Wales Council for Intellectual Disability, said the practice of using medications to restrain people was referred to as "chemical restraint" and its use was restricted.

"Chemical restraint is the use of a medication that restricts the freedom of movement of a person with a disability," she said.

"It is often used in cases where they may be at risk of harming themselves or somebody else.

"We believe that it is often used in place of positive behaviour support."

Specialists said cases like Jason's were not unique.

Neuropsychiatrist Professor Julian Trollor is chair of Intellectual Disability Mental Health at the University of New South Wales.

He said psychotropic medications, in particular anti-psychotics, were typically used to treat psychosis associated with conditions like schizophrenia and bi-polar.

"The majority of prescriptions are in fact being given for challenging behaviour as opposed to control or adequate treatment of psychotic symptoms," he said.

"Unfortunately the evidence-base for the use of medications and anti-psychotics in this manner is very limited.

"We do know that this is a problem we know that it does need to be addressed."

He said there was a role for all levels of government to play.

"There is an urgent case for upskilling nurses, doctors and disability professionals in the appropriate use and role of psychotropic medications," he said.

The Australian Medical Association NSW branch said more work needed to be done to help GPs coordinate care between other providers.

Jason is now living with a private care provider and his behaviour has improved dramatically.

Ros Phillips is responsible for the care of her autistic son Jason who suffered a medication overdose. ( ABC News )

Watch the story tonight on Lateline at 9.30pm (AEST) on ABC News or 10.30pm on ABC TV.