The families of several mentally ill West Australians who were treated at a Fremantle psychiatric unit before taking their own lives say an investigation has highlighted gross inadequacies within the mental health sector.

Five patients from the Alma Street Centre killed themselves between 2011 and 2012, prompting the state coroner to examine the cases.

One of them was 18-year-old Ruby Nicholls-Diver.

The teenager took herself to Alma Street in 2011, where she was treated for a complex mental illness for four days.

Just hours after she was discharged, Ruby's father Geoff Diver found out she was dead.

"She gathered up her handbag with her ID, she wrote all of my details in it, and she walked about a kilometre to a park, and she took her life."

In the four years since her death, Mr Diver has fought for the mental health system to be overhauled, and believes his daughter's death could have been prevented.

"I still think about her every day, there would not be one day go past where you don't," he said.

The teenager first began harming herself when she was just 10 years old, and by the age of 18 she told her doctors she was exhausted just trying to keep herself alive.

"We had this, not quite a merry-go-round, but this ongoing hospitalisation throughout her adolescence," Mr Diver said.

Given Ruby's history, Mr Diver was alarmed when he found out she was being discharged from the Alma Street clinic.

Just two days before, she had tried to take her own life.

"How do we take an 18-year-old into hospital through triage and admit her as having suicidal ideation, have her attempt to take her own life on the ward as an inpatient, and then discharge her?" he said.

Geoff Diver says he thinks about his daughter Ruby every day. ( ABC News: Claire Moodie )

System 'in disarray': Geoff Diver

Ruby's death, and the suicides of four other West Australians, have been the subject of a recent Western Australian coronial inquest.

The findings will not be handed down for months, but Mr Diver said the evidence highlighted a system in disarray.

"You've got these people who are already grappling with the notion of failure, and the system essentially invites them to fail every step, and make you feel like a failure every step," Mr Diver said.

A few months after Ruby's death, Moira Thomas' husband Michael also committed suicide after being discharged from the Alma Street clinic.

"It was a complete and utter balls-up for want of a better word," she said.

"It was completely despicable what happened."

Mr Thomas had been battling depression since he was made redundant from work.

He was admitted to Alma Street after a suicide attempt, but the following day, doctors told his wife he would be discharged.

Moira Thomas said what happened to her late husband Michael was "completely despicable". ( ABC News: Claire Moodie )

Pleas for help fell on deaf ears: wife

She resisted and told staff her husband needed to be in a locked ward and reviewed by a psychiatrist.

However, Ms Thomas said her pleas fell on deaf ears.

"The following day, I get a phone call - I'm at the other side of the city - to say he'd been discharged, wearing slippers, in borrowed clothes, and was given a smart rider [public transport ticket]," she said.

"Now to me you don't even treat a dog like that, never mind someone who is severely mentally ill."

The day after he was discharged, Mr Thomas woke up distressed.

Ms Thomas told him she would take a shower, before driving him to the hospital.

It was the last conversation she had with her husband.

"When I was in the shower he just walked out ... and was never seen again.

"He was found dead in the bush 13 weeks later."

Mental health beds 'never get cold'

Shortly after the deaths of Michael Thomas, Ruby Nicholls-Diver and three other patients at the Alma Street Centre, an independent review was commissioned by former WA chief medical officer Professor Bryant Stokes as concerns about the system mounted.

It painted a damning picture of an overworked and under-resourced mental health sector, which was failing people and costing lives.

Ruby Nicholls-Diver began self-harming from the age of 10. ( Supplied: Diver family )

The review was welcomed by Mr Diver, who said there was a severe bed shortage within the sector.

"It reflects the elephant in the room, certainly the elephant in the room from the Government's perspective - where nobody is prepared to use the term 'bed-shortage'," he said.

"There's people working under pressure and there is a bed shortage.

"I'm pretty sure none of the beds in the mental health system in Western Australia ever get cold."

The State Government said it was addressing the gap.

There are currently 1,283 community and hospital beds around the state, and the State Government's draft Mental Health plan indicates that number will grow to 1,521 by 2017.

Mental health 'neglected for decades': Minister

Mental Health Minister Helen Morton conceded the system had been under stress, but said the sector had been neglected for decades.

"This government has made mental health a priority," she said.

"We were the first government to establish a mental health commission - of any state or the nation - we have a dedicated ministerial portfolio for mental health.

Five patients who had been treated at the Alma Street clinic killed themselves between 2011 and 2012. ( ABC News: Nicolas Perpitch )

"Our funding for mental health services has increased by 77.7 per cent since 2008-09 and that is the third highest level of growth of any agency."

Ms Morton said in the three years since Professor Stokes' review was released, the Government had implemented about a third of its recommendations, and was in the process of addressing the remainder.

"There are a number of things taking place at the moment," she said.

"It takes a reasonable amount of time to make these things come to fruition so developing the sub-acute facilities for somebody to be transitioned into ... you have to purchase the land, put up the building design, go out to tender, get the building completed, do the commissioning etcetera.

"These things take time."

Mr Diver said while the promised changes looked good on paper, he was not convinced the Government would be able to effectively implement them.

"I really think it's yet to be seen, I don't have full confidence that it will happen as smoothly as people think," he said.

He hopes the findings from the coronial inquest, expected later this year, would keep the issue on the public agenda.