Four out of every five young New Zealanders have been physically punished - with half of them still being hit in adolescence.

The findings, from two Otago University papers published in the New Zealand Medical Journal, paint a grim picture of violence that health professionals say still exists.

The findings come from the Dunedin Multidisciplinary Health and Development study of nearly 1000 people born in Dunedin in the early 70s. The subjects - now all in their 30s - are interviewed every three years.

Nineteen per cent recalled violence between their parents ranging from slaps and shoves to life-threatening beatings, while a further 6 per cent reported threats only.

Eighty per cent reported physical punishment and discipline in the home during the 1970s and 80s. A quarter reported smacking as the most severe physical punishment - but 45 per cent reported being hit with an object. Six per cent described extreme physical punishment such as being beaten up or knocked unconscious.

The results suggested parental use of corporal punishment was the norm in New Zealand, said Dr Jane Millichamp, lead author of the paper on physical punishment.

"Not only did we find that physical punishment was extremely prevalent, it was also administered over a long time period in many cases."

Dr Millichamp said girls were more likely to receive lower-level punishment such as being smacked with an open hand, whereas boys were more likely to be hit with objects.

But when it came to extreme physical punishment - such as being struck with whips or repeated kicking - there was no difference. Dr Millichamp said that in many cases, punishment appeared in the form of "blind rage", regardless of the child's age, gender or actions.

The lead author of the domestic violence paper, Judy Martin, was surprised by the detailed accounts of events witnessed years before. Regardless of whether violence was carried out or threatened, the subjects remembered it as very upsetting, she said. They were more likely to be diagnosed with anxiety or depression at 21, although it was not clear if it was directly related.

Public Health Association director Dr Gay Keating said the results were saddening, but not surprising.

The findings would help to shatter "the mythology that says there's only some sorts of people or some sorts of communities who are violent".

Violence would have a marked impact on those children, even in adulthood, she said.

"The very first thing it does is destroy the idea that home is a safe place."

Repeated exposure to violence could desensitise, and children in abusive environments were more likely to be abusive as adults.

One step towards reducing violence was Green MP Sue Bradford's bid to remove the legal defence of "reasonable force" in the Crimes Act.

"It has a very high symbolic value in that it says assault of adults or of children is not okay - and it will give children the same protection as we give dogs," said Dr Keating.

Family counsellor and author Rhonda Pritchard thought more parents were not using physical punishment, but recent data suggested it was still common. "Part of the problem is that people believe it's necessary because they don't know people who haven't been hit."

Professor Anne Smith, director of the Children's Issues Centre in Dunedin, said studies in the late 90s found parents still hit their children at least once a week.