A leading paediatrician says tens of thousands of New Zealand adults could have an undiagnosed brain injury, sustained through being abused as a baby.
A study published in the international medical journal, The Lancet, found New Zealand's rate of traumatic brain injury to have been grossly underestimated and is about 3000 a year - much higher than in other developed countries.
Each year, the child protection team at Starship Hospital sees about 20 children under the age of three with brain damage caused by abuse.
Its leader, Patrick Kelly, says an American study suggests that for every case they see, 150 go unreported because the abused child is not injured so badly as to require hospitalisation.
Dr Kelly says he believes thousands of New Zealand adults could have learning and behaviour difficulties because of childhood brain injury.
Meanwhile, children's safety organisation Safekids is going to the country's young for advice on increasing helmet wearing.
Research released in November indicates the incidence of brain injury from a blow or bump to the head - from all causes, not just child abuse - is at epidemic levels in New Zealand, at about 36,000 cases a year.
Safekids says anecdotally, there is a decline in helmet use from about nine years old and it's no coincidence that brain injuries from cycling accidents are higher from this age on.
It says it is difficult to get through to this age group so it's is launching a national competition in February to get students to come up with ideas about helmet wearing to which they, themselves, would respond.