The Ministry of Transport has removed from the official road toll 15 deaths in the 15 to 24 years age range because they were judged to have been suicides.
Four of the deaths in the toll between 2000 and 2008 were of pedestrians, and 11 were drivers, said a spokeswoman for the ministry.
She was commenting on Australian research which surveyed newly licensed drivers aged 17-24 in New South Wales to ask if they had engaged in self-harm in the previous year.
A total of 871 (4.6 percent) had attempted true self-harm: cutting and burning, poisoning, self-battering, road-related harm, risk-taking and attempted suicide.
Over 58 percent of these people were women, and self-harm was most common among the youngest drivers, with 52 percent of those reporting self-harm aged 17.
The research was published in the Canadian Medical Association Journal, and showed just over 10 percent had at least one crash and nearly as many were involved in multiple-vehicle incidents.
"Self-harm was found to be an independent risk factor for motor vehicle crash among young drivers who engaged in self-harm," said Dr Alexandra Martiniuk, of the Sydney-based George Institute, who was a co-author of the study.
In New Zealand, an MOT spokeswoman said it was excluding from the road toll deaths where a coroner had ruled it was self-inflicted, but there was no guarantee it sighted all the relevant rulings.
She said the ministry was not conducting any specific research in this area, such as whether interventions among younger drivers to address self-harm might be helpful.
A spokeswoman for the ministry said self-harm and risk-taking behaviours like alcohol and drug use and risky driving were likely to be related.
"In fact, self-harm can include these behaviours," she said.
A New Zealand survey in 2007 showed 16 percent of male students and 25 percent of female students had deliberately self-harmed in the previous 12 months. Most of the injuries were minor - with only 3 percent requiring medical treatment, but they could have included "risky driving".
