Frank Rawlinson believes synthetic cannabis could cause society similar problems to the drug P.
But the clinical director for mental health and addiction services at Whanganui District Health Board points out a couple of differences: synthetic cannabis is legal and while P, or methamphetamine has one formula and a relatively consistent effect on people, synthetic cannabis is all over the shop on both counts.
On the back of a picket in Victoria Ave protesting the legal sale of synthetic cannabis, which comes under the Psychoactive Substances Act, Dr Rawlinson says councils need to step in now and regulate what happens on their streets. It is a "resource hungry, worrying and significant issue for the Wanganui community".
"Eight years ago Australia was almost brought to its knees because of the unbelievable violence that hospital emergency departments had to deal with from those who were under the influence of P-methamphetamine."
He is worried hospital staff are now having to deal with people under the influence of synthetic cannabis which is not only legal but has variable ingredients and thus unpredictable effects.
He says while it will take a Government approach to change the law, local councils do have the ability to influence the sale of these substances in their communities.
"It is my understanding that council/s have the ability, through the new legislation, to determine what happens within their communities in regards the sale of synthetic cannabis or similar.
"Council needs to execute their civic duties in a manner that they see fit after due consideration of the competing needs of their constituents."
Dr Rawlinson said the community was often at a disadvantage as they did not have all the details with which to make an informed decision.
"The community is also conflicted between the wish to preserve the freedom to act as they see fit and the desire to protect the vulnerable within society."
If alcohol was invented today, there would likely be a similar outcry, he added.
"These chemical substances can be highly dangerous and it is my personal view that the onus - to prove that they are safe - should rest with the manufacturers and suppliers."
The picket on Wednesday outside Stardust Creations was organised by community leaders Ken Mair and Philippa Baker-Hogan. It attracted about 50 people.
"Mr Mair and Ms Baker-Hogan clearly have strong views and I assume that they are making a stand to protect the vulnerable within our community. It is a free society and they are displaying the courage of their conviction," he says.
"Synthetic cannabis is made up of a variety of chemical compounds that are rapidly changing and variously mixed. Their effects are those not readily predictable as it depends on the mix of chemicals in any particular offering.
"We do however know that the effects are bad and unresponsive to treatment."
Dr Rawlinson said only last week a woman admitted to WDHB mental health unit Te Awhina told staff she loved Tai High (a form of synthetic cannabis) so much she wished she could marry it.
And there were those long-time users of cannabis who did not want to get into trouble, who switched to synthetic cannabis because it was legal, Dr Rawlinson said.
He sees people on an ongoing basis in a clinical setting who are suffering the effects of using the substances and this is echoed by other clinicians.
Furthermore, Dr Rawlinson says, substance use in general has not reduced, cannabis has become stronger, and those selling it could "lace" it with a stronger chemical.
The use of these substances is not age limited, although the law says the substances cannot be sold to those under 18 years.
Dr Rawlinson says mental health and Emergency Department staff are seeing users as young as 15 who are angst-ridden with no protection of a home.
Those who did present in an acute situation were "thought-disordered, and aggression is a significant part of their behaviour".
"From a clinical perspective their presentation does not take the form of what we are used to."
A consequence of those who came to the mental health unit under the influence of synthetic drugs, was that they often needed to be restrained and secluded.
In the past 12 months in-patients requiring seclusion were all influenced by synthetic drugs.
"We normally have a very good idea [of what actions to take] once people are admitted. However this no longer applies once you bring in these substances.
"People who are very intoxicated [with alcohol or synthetic drugs] do not represent a health problem but a public safety and order concern," Dr Rawlinson says.
"It makes them feel invincible. They lose human warmth ... they can't reach out to other people, their humanity is lost and they are unpredictable. In fact, their behaviour is scary, very difficult and awkward."
Dr Rawlinson says it becomes a police matter because of the safety of the community and the hospital staff who have to treat these people.
"These presentations add a totally different and new layer of complexity at the hospital which is not equipped to deal with what in essence are matters of intoxication rather than illness."
Dr Rawlinson says in some cases people are not held accountable if they are admitted to the mental health unit (under the Mental Health Act) because they are unlikely to be charged with an offence.
He thinks they should be.
"The police are responsible for public order and safety. They have a set of guidelines or rules that govern their response to public disorder and intoxication, especially of alcohol.
"Intoxication with other substances, such as these, are no different and should be similarly dealt with.
"Consistency in dealing with these issues by the police and individual accountability for actions and behaviour is likely to have a much better long term outcome for society as a whole."