Cannabis use is causing more admissions to publicly-funded hospitals than all of the other illegal drugs combined, a police drugs specialist has found.
Police are not yet revealing full details of the findings in a new report by National Drug Intelligence Bureau strategic drug analyst Les Maxwell.
Details of the report, titled: New Cannabis: The Cornerstone of Illicit Drug Harm in New Zealand, follow yesterday's release of a Drug Harm Index which found New Zealand's drug use cost $1.3 billion in 2005 and 2006.
Parts of the report released to the Herald last night show there were between 2205 and 2512 cannabis-related admissions to publicly-funded hospitals between 2001 and 2005.
Hospital admissions relating to all other illicit drugs, including P, ecstasy, cocaine and heroin, ranged from between fewer than 1500 to 2000 during the same period.
Officers at the NDIB were last night remaining tight-lipped on why cannabis featured heavily in admission statistics. But the Drug Harm Index shows cannabis is the most widely used illegal drug in the country, with 373,310 users - well above the next most popular drug, amphetamines, with 95,170 users.
The reasons for hospital admissions due to cannabis use include mental illness, psychosis and accidents.
The drug harm index was designed by economists to help police and other agencies decide where drugs do the most harm and enable them to use resources more efficiently. Police spokesman Jon Neilson said police already had intelligence which helped them focus on the drugs which caused harm but the index was another tool to assist that.
National Drug Intelligence Bureau co-ordinator Stuart Mills said while police have known the street value of drugs seized in the past, they have never known the social impact of removing it from society.
A big advantage of the index was that police would now be able to not only give the street cost after a big raid or seizure, but also say what the social savings were.
"We have never had anything to say what are we achieving ... I suppose this is giving us a measure."
That kind of information could also be helpful for appealing for funds in future police budgets.
"If I wanted to ensure I got my fair share of the budget within police and I had to proof what I was going to achieve in various operations, then that's a very helpful tool."
Mr Mills said the index illustrated to the community the wider social impacts.
"We are not just talking about the drug harm to someone else. The use of illicit drugs within the community is affecting all of the community ... we have seen the impact in various stories of violent crime and addiction."
Meanwhile, Associate Health Minister Jim Anderton said while illegal drugs cost society, the harm was dwarfed by that caused by legal drugs alcohol and tobacco.
"If you ask the police, or medical authorities, about the times they are called in to crises, or to accidents, to clean up human harm they will tell you that alcohol is almost invariably involved."
Mr Anderton said tobacco caused about 4700 deaths each year, and the social cost of alcohol misuse was $1.5 billion to $2.4 billion a year.
"If any other drug caused that number of deaths, there would be rioting in the streets. So why do we make alcohol legal, when it causes much more damage than any other drug? Why can we buy tobacco, a killer drug, at the corner dairy?"