A ban on legal highs in Edinburgh is responsible for a drop in crime, according to a report due to go before Edinburgh City Council.
The news comes as police crackdown on sellers following the introduction of the Psychoactive Substances Act 2016.
The ban was introduced in the capital a year before the law was changed and while the act makes it illegal to sell NPS including Clockwork Orange, Black Mamba and Annihilation, possession is still legal.
Author of the report, Rob McCulloch-Graham, chief officer, Edinburgh Health and Social Care Partnership said: “At this time, Police Scotland reported an increase in bizarre anti-social act behaviour and extreme violence. Police reported that these incidents involved people who appeared to be under the influence of a stimulant based drug, likely to be ethalphendrate.
“The most serious of these resulted in an officer being stabbed, a siege and a suicide.
“Local evidence suggests that between January and October 2014, there were 39 incidents where the police were called and the person was taken to A&E, as well as a number of incidents of violence linked to extreme behaviour.”
He added: “In summary, the introduction of the temporary banning order for ethalphendrate in April 2015 had a significant impact on the availability and use of this drug.
“This resulted in a reduction in a range of health and criminal harms relating to drug use.”
Deputy chief constable Ruaraidh Nicolson said: “We have engaged with known sellers of NPS to make them aware of the introduction of the Psychoactive Substances Act 2016.
“There is no safe way to take NPS, there is always a risk.”