A report on teenage social problems says people who sell drugs to young people should get harsher penalties than those who supply the general population.
The report was prepared by researchers for the Prime Minister's chief science advisor, Sir Peter Gluckman, and considered high levels of teenage suicide, drug use and pregnancy.
It says adolescent cannabis users have an increased rate of psychosis, anxiety and depression, educational under-achievement and risk from traffic accidents.
Because of this, the report says, people who supply cannabis to those under the age of 18 should incur stiffer penalties from the courts.
Anti-drinking campaigns ineffective
The report found alcohol abuse to be widespread among young New Zealanders, with one-third of 12- to 16-year-olds engaging in binge drinking.
But it says research shows measures to curb problem drinking, such as health warnings on bottles, mass media campaigns and alcohol education programmes in schools, have little effect.
The report says increasing taxes on drink and restricting its availability do work. It says crackdowns on drink driving can also be effective, and limitations on alcohol marketing and advertising can have a modest impact.
High level of sexually transmitted diseases
The report also calls for improved counselling so that young New Zealanders are less likely to incur sexually transmitted diseases or have children of their own at a young age.
It says the level of sexually transmitted diseases is high in New Zealand, while teenage pregnancy rates are six times higher than in the Netherlands.
The report says researchers universally agree that teenage motherhood is a bad thing, and say current methods of dealing with it, such as sex education at school, have mixed results. It says advanced countries with low teenage pregnancy rates tend to have easy access to sexual health services.
The research, presented on Wednesday, was the result of an 18-month study commissioned by the Prime Minister.