At least four research applications related to suicide and the Christchurch earthquakes were declined funding over the past five years.

These rejected research proposals were a lost opportunity for New Zealand and the world, experts say.

Documents obtained through the Official Information Act (OIA) show at least four applications to study the correlation between the quakes and antisocial behaviour, including domestic violence, post-traumatic stress disorder (PTSD), self-harm and suicide, were declined.

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The results would have had "enormous international value," said clinical psychologist and post-disaster expert Dr Rob Gordon.

Christchurch was a unique opportunity to study this area and the research could have put New Zealand on a world stage for analysing post-disaster suicide or self-harm trends, he said.

Earlier this year, a Herald investigation into hundreds of coronial reports found 40 people had taken their own lives linked to the Canterbury quakes between 2010 and 2014.

Most were suffering from pre-existing mental health conditions that were exacerbated in the aftermath of the disaster.

The Herald's investigation found these self-inflicted deaths had never been connected before, probably because research applications to study this area had been declined.

Dr Gordon, who is a disaster consultant for Red Cross Australia, said "a post-mortem on those cases would have been 'enormously helpful"'.

"If we can find out what pushes people over the edge then that's what helps us to do more to prevent this," he said.

Professor Annette Beautrais, one of New Zealand's lead suicide researchers, sought funding to study the possible correlation between the quakes and suicide more than two years ago. All of her applications were declined.

Dr Pauline Gulliver, Auckland University research-fellow, was declined funding from the Health Research Council in 2012 to study the quakes, domestic violence and self-harm.

Her application was denied due to a lack of information and a confusing method of study, documents show.

"There is not an unlimited pool of funding and some applications will take priority over others," Dr Gulliver said.

However it would have been "really, really interesting" to investigate how the post-quake environment had impacted suicide, self-harm and PTSD, she said.

Christchurch's suicide rate did not increase post-quake, but these deaths still should have been monitored, said Professor Alexander McFarlane, director of the University of Adelaide Centre for Traumatic Stress Studies.

Disaster research is challenging because the events are often infrequent, unpredictable and occur in diverse locations, he said.

Christchurch's health infrastructure remained afloat after the disaster, leaving it in a unique position to conduct research which could have led to changes in international policies.

"This was a lost opportunity for New Zealand and a lost opportunity for the international community," Professor McFarlane said.

One of the failed research applications outlined how the Canterbury quakes had provided a rare opportunity to research clinical, hormonal and neuropsychological aspects of stress response. The application was declined by the Health Research Council because of limited funds and "higher priorities in other areas".

Of the 40 individuals who took their lives linked to the quakes, most were suffering stress, anxiety, paranoia and fear, but some became severely depressed after battling the Earthquake Commission and insurance companies.

In March, the Health Ministry announced a $20m boost to increase mental health support for the people of Canterbury and it continues to work closely with a range of agencies on the ground, mental health director Dr John Crawshaw said.