Mental health, addictions and intellectual disability services nursing director Heather Casey said patients were displaying high levels of aggression after consuming synthetic cannabis.
She believed the community was largely unaware of the extent of the problem.
Synthetic cannabis withdrawal was severe, and patients struggled to break the addiction, she said.
''At the moment, it's all sort of behind closed doors. We felt it was really important in terms of people making decisions around the selling of synthetic cannabis, and at a Government level, that people are aware of the impact synthetic cannabis is having on mental health services,'' Mrs Casey said.
Increasing alcohol abuse was an issue, too.
The forum would be held in Dunedin in May or June and would involve politicians, police, other health services and other interested parties. Inpatient mental health services, community mental health and the community alcohol and drug service would all be involved.
The same issues were being experienced in Southland, and the forum would cover the whole health board.
''What we're seeing is some change, particularly in acute inpatient environments, around the people being admitted to services with increasing aggression, really, and that is partially linked to the increase in use of alcohol substances and synthetic cannabis.''
Synthetic cannabis was a factor in a rise in assaults reported by health staff, she said.
Information released by the health board reveals a big increase in assaults in the mental health service. However, the bulk of the increase was not caused by synthetic cannabis.
The biggest jump was in specialist mental health services, where Otago staff reported 59 assaults in the six months to the end of February, compared with 15 assaults in the corresponding period the previous year. That increase is being attributed largely to a single patient, unrelated to synthetic cannabis use. Assaults in the adult mental health service (Otago) increased from 34 to 40 over the same period.
Staff had good support in dealing with the individual patient and the wards were well resourced, Mrs Casey said.
Sometimes, the specialist service admitted acutely disturbed patients, and it could take a significant period of time to help them with their issues.
''The reality is, there is nowhere else we can send people. We have to find ways to help them get well, and sometimes that takes a long period of time,'' Mrs Casey said.
No assaults on Otago staff were recorded in the emergency department, compared with two in the previous period.
There was one assault in both public health and the surgical ward, compared with none the year before.
Recorded assaults included verbal incidents.
