The family of Stockton's Kahi Simon is furious that a Hunter New England Health investigation into his suicide excluded important factors that led to his death.

Kahi took his life at age 20 on October 1 last year, five days after being discharged from Taree Hospital's mental health inpatient unit.

His mum Kelly Kay and step mum Katrina Mason believe Kahi should not have been discharged from the hospital.

They made this clear in an interview with a health department investigator that lasted more than three hours.

They were alarmed that their concerns were not included in Hunter New England Health's "serious adverse event review" into his death.

They were also angry that crucial details of Kahi's 10-day stay in the Taree unit were not included in the report.

Ms Kay, of Merewether, said the investigation "only showed where the system failed him after he left the hospital".

Dr Anand Swamy, Hunter New England Health's executive director of mental health services, said the district "offers its sincere condolences to Mr Simon's family and friends for their loss".

Dr Swamy acknowledged the "grief they are experiencing at this difficult time".

"Due to patient privacy we are unable to provide further details."

Kahi [pronounced Ky] grew up in Stockton and went to Newcastle High, but also lived in Forster. He had Indigenous heritage with the Worimi people.

The Newcastle Herald reported this week that Ms Kay was campaigning for 24/7 safe havens for people in crisis.

She said her son needed this when he came out of Taree's mental health unit.

He was admitted there on September 10, after a failed attempt on his own life.

Ms Kay said he went missing from the hospital three days later.

"They informed us when we went to see him," she said.

"The police found him and took him back."

Miss Mason said it was disturbing that he had been able to "walk out the front door of the hospital, even though he was incredibly unwell, disoriented and a huge risk".

The report stated that Kahi had "approved periods of supervised leave with family" from September 14 to 19.

It stated that this leave was "reported to have gone well".

Overnight leave from the hospital was granted on September 20.

On September 26, Kahi was discharged from the hospital after a telehealth meeting with him, his family and staff.

"When he was discharged, we asked if he could stay on as a patient. They said no, they thought he was doing well enough," Ms Kay said.

She said the hospital told the family that "someone would follow up", but they didn't hear anything for three days.

When Kahi's mental health deteriorated, his stepfather contacted the hospital on September 29.

He discovered Kahi had been transferred from the acute care team to the "brief intervention team".

"We weren't informed about this," Ms Kay said.

The report showed that the acute care and brief intervention teams had been unable to contact Kahi.

Miss Mason said they had been "contacting him on a mobile phone that he didn't have anymore".

Ms Kay added that she had "told them numerous times that they should call me".

"I gave them my number," she said.

As Kahi's condition worsened, he told his family he wanted to return to the Taree hospital.

Miss Mason alleged that the hospital "made him believe that the minute he struggled, he could pack his bags and walk back in".

Ms Kay agreed, saying "they made it clear to all our family that he was welcome to come back if needed".

But when she called to check if he could return, "they said we need to go to the Mater in Newcastle - you can't come back here".

The report recommended that mental health units "ensure patient contact details are correct on admission, when placing a patient on leave and/or discharge".

It also found a "variability in compliance" with the transfer of care.

This led to "the clinical ownership of the patient" being "unclear" between the acute care and brief intervention teams.

Because of this, the report found no follow up occurred with "the patient or their family" from his discharge to September 29.

Ms Kay said a member of the brief intervention team should have been on the telehealth call that discharged Kahi, so the transfer of care was clear.

The report recommended a review of discharge meetings with patients and families.

This was needed to ensure patients and families had "opportunities to confirm the patient's care plan".