A man who fractured his skull in a car crash when he was 13 and later developed schizophrenia has won a landmark battle with ACC for compensation.
Wellington District Court ruled the man's injuries were likely to have caused him to develop the mental health disorder - a decision his lawyer says opens the door to other sufferers filing similar claims.
The man, whose name is suppressed, received initial ACC cover after suffering a skull fracture, bleeding in the brain and brief amnesia in the 1988 crash.
But three years later he started having sound hallucinations, and at 18, a full psychotic episode.
He was eventually diagnosed with paranoid schizophrenia - a severe brain disorder in which people struggle to cope with reality.
ACC rejected his family's bid for cover, saying they could not prove the accident and the disorder were connected.
But Wellington District Court has backed the family's appeal, and their lawyer Hunter de Groot said it was a landmark win.
"It's the first time we've had a case where the link between adult psychosis and a traumatic brain injury has filtered into accident insurance litigation," he said.
He said the decision opened the door to many sufferers of schizophrenia and other psychosis.
"If people have a traumatic brain injury in their past and they've gone on to develop schizophrenia then they should by all means consult their GP about a possible claim - we've now established a legal link between the two."
ACC's medical experts rejected the link between the crash and the man's schizophrenia, but Judge Neil Maclean ruled the contrary evidence presented by the man's personal psychiatrist more credible.
A spokesperson for ACC, Stephanie Melville, said the corporation would not appeal.
"As the judge noted in his decision, the court's assessment of causation can differ from the experts' opinions and can infer causation in circumstances where the experts cannot," she said.
"The judge was also able to consider new evidence not available at the time of the review hearing. ACC accepts the findings of the court."
Auckland University last week released its own research on schizophrenia.
It too favoured the nurture over nature argument and said there was a strong association between personal trauma and the development of schizophrenia.
A co-author, Tony O'Brien, even warned ACC to expect an impact on the number of claims it accepts.
"The decision could also have an impact on the low numbers of sensitive claims for independent allowance currently approved by ACC in New Zealand," he said.
Mental Health Foundation chief executive Judi Clements said it was vital more people got help from ACC.
"ACC can be a gateway for people to get the help they otherwise couldn't afford because things like counselling and psychological therapies aren't available free of charge."
She said schizophrenia was a controversial disorder and one surrounded by misconceptions.
"It's still one of those labels that can be misunderstood and often that label is used by some of Hollywood's scariest films - of someone who is dangerous and out of control," she said.
"That needs to change."