The Health and Disability Commissioner legislation calls patients "consumers".
The DHB todayacknowledged the deputy commissioner's findings and said it "sincerely apologises for systemic issues contributing to the failings in this case".
Aged in his 40s, the man, unnamed in Allan's report, had had a long history of mental health and addiction problems. He was first referred to the DHB's mental health and addiction service in 1995.
Friends complained to the commissioner's office about the care the man received in the months before his death.
He was admitted to a public hospital in 2015 after self-harming. He was diagnosed with adjustment disorder, alcohol dependence and antisocial personality disorder.
This began a three-month involvement with the DHB - and at times the police - which included voluntary admissions to an acute psychiatric unit, and outpatient care.
On one occasion when he was discharged from the unit, a nurse recorded that the man continued to be a moderate to high risk in the community for harm to himself and others.
Allan's report notes that the man had sent inappropriate text messages to a female worker at the alcohol and drug service.
At the multi-disciplinary team meeting at which the man was discharged from the alcohol and drug service, a risk assessment recorded that he was at chronic risk of suicide.
Allan said he acknowledged the needs of the man, "Mr A", were complex and that he required support from both mental health and addiction services.
"However, it was the role of the South Canterbury DHB and its staff to provide Mr A with appropriate and adequate care, taking account of that complexity."
He said that although individuals bore responsibility for some of the shortcomings in the man's care, "overall I consider many of the failings exhibited in this case to be systemic issues for which SCDHB is accountable".
Allan said the DHB had implemented professional supervision for clinical staff in the alcohol and drug service, in response to his earlier, draft findings.
His final report's recommendations include making an assessment of mental health and addiction services and reviewing policies on staff sexual safety, incident reporting and the discharging of patients.
In a media statement today, the DHB said: "The client's needs were complex and required support from multiple agencies; however it was the role of the DHB and its staff to provide the client with appropriate and adequate care, taking account of these complexities.
Changes had been made to protocols on how to handle complex-case reviews, including how service users and their families/whānau could be more involved in the process.
The DHB expected to report to the commissioner's office within six months on the findings of an external review into the services provided to people who have both mental health and addiction issues.
Additionally, the DHB said, South Canterbury's mental health and addiction services were being assessed to ensure they meet the needs of the existing and emerging population.
Need help?
• Lifeline – 0800 543 354 (0800 LIFELINE) or free text 4357 (HELP)
• Suicide Crisis Helpline – 0508 828 865 (0508 TAUTOKO)
• Healthline – 0800 611 116
• Samaritans – 0800 726 666
• Depression Helpline – 0800 111 757 or free text 4202 (to talk to a trained counsellor about how you are feeling or to ask any questions)
• Youthline – 0800 376 633, free text 234 or email talk@youthline.co.nz