Massey researchers are questioning a report which they say overlooks the risks that'll come with legalising cannabis

The Sense report projects up to 249-million-dollars could be collected in tax and licensing fees from legal cannabis sales.

But, in a New Zealand Medical Journal article, Massey University researchers say this must be balanced against the additional health and social costs from increased cannabis use.

Co-author and Massey University Associate Professor, Chris Wilkins says the report assumes there'll be no additional harm from cannabis under legalisation.

He says the point of cost benefit analysis isn't just to show the most optimistic outcome, but to also show the level of risk.