It does not cause any physical or permanent damage whatsoever but actually has pain relief benefits. This is why in places like California cannabis is legal for medical use and can be purchased in dispensaries located in pretty much every city in the state. To purchase it you must have a medical prescription from your doctor. This is a very successful system and for people who need it such as those going through chemotherapy, it relieves their pain and gives them a better quality of life.
In terms of the New Zealand Economy the sale of Cannabis would be very good for New Zealand as it could be taxed just like tobacco and there would be much less drug convictions so that there would be less of the tax payers money going towards prisons and more money going towards community projects. Massive police resources are wasted on minor drug offences in New Zealand. A considerable proportion of New Zealanders have smoked cannabis and many users are normal healthy contributing members of society.
Police time and money is wasted on a relatively harmless drug. If legalised, citizens could use marijuana without the risk of sponsoring drug lords and crime, as people would no longer need to go to gang affiliated drug houses to get their marijuana but could purchase it from a local dispensary. If legalized the same laws that apply for alcohol could apply to marijuana, things similar to the liquor ban zones, the age limits for buying and using it and no driving under the influence. Negating Statement Now for the reasons that marijuana should not be legalized.
There are some health risks with marijuana, it does minor damage to the memory and if smoked reduces your lung capacity by 10%. Other than pain relief it doesnt have any health benefits whatsoever therefore medical marijuana is a bit of a myth. Legalizing cannabis would also make other illegal substances seem much less serious and normalize the use of drugs in New Zealand, making it seem okay to do drugs for the next generation. Ask yourself this, do you want NZ children to be raised in a country where drugs that could be harmful exist and can be used by anybody?