The co-response team was established in the city in 2021 to bring together police officers, paramedics and mental health nurses in attending callouts.
The number of emergency psychiatric services (EPS) referrals had fallen 14.1%, a report praising the co-response programme said.
But internal emails from Te Whatu Ora Health New Zealand (HNZ) show concerns were also raised, including a lack of evidence for some positive feedback and concern about how well the programme would function without St John taking part.
The documents were recently released by HNZ Southern under the Official Information Act.
An HNZ Southern feedback report said there had been increasing demand for EPS in recent years, negatively affecting the service it was able to provide.
From November 2021 to March 2023, the co-response team received 14.1% of a total of 3173 referrals, while the EPS received 85.9%.
However, 22% of co-response referrals were brought through to EPS or the emergency department (ED).
The report noted the programme operated from Tuesday to Friday and only until 9.30pm, whereas EPS was a 24/7 service.
Overall, the programme was beneficial, the report said.
Relationships between police, mental health services and St John had improved, and clients and their families had "significantly better experiences and outcomes".
Clinicians found working collaboratively to help people in crisis in their own homes to be "extremely rewarding".
Feedback from clients and family testified to the value of this, the report said, although it did not cite any such feedback.
People who might previously have been brought to HNZ Southern services were now often able to be assessed and treated in the community.
Anecdotal evidence was that fewer people were brought to EPS or the ED in restraints.
This reduced levels of trauma on admission and could mean inpatient services worked more effectively, the report said.
The programme had also streamlined the process for a client being taken to EPS by a paramedic, as they could carry out physical assessments, which reduced waiting times in ED.
The Otago Daily Times previously reported St John was no longer part of the co-response team, having left the programme in June.
In an email from July, HNZ Southern raised concerns about how well the programme would work.
Paramedics helped reassure people requiring police intervention that the team had a health focus, and improved wait times.
Role confusion in crisis services was another issue, with police overall taking the lead.
When police should be involved was an area of contention, which had "created delays and issues".
If people were in mental healthcare, it was that service’s responsibility to manage, the notes said.
Police were "very enthusiastic" about extending the co-response programme to Invercargill and were pushing for this to occur, but HNZ noted it was hard to staff mental health services.
Some of the stated benefits of the programme did not have good data, while the data HNZ did have required "a bit of working through".
An evaluation by police was also criticised, with "outcomes described but no evidence given", including a lack of patient and family feedback.
The information provided by HNZ also showed 209 responses recorded as part of the programme between January 1 and October 6 this year.
HNZ was unable to break down this number to show which agencies were present, but said it was likely both police and paramedics had attended all instances until June.
