Research published in the prestigious American journal JAMA demonstrates fears that gun suicides would merely be replaced by other methods have proved misguided, with an initial spike in suicide deaths immediately following the buyback followed by a steady downward trend.

The rate of homicide deaths, which were already in decline, declined further.

University of Sydney Emeritus Professor Simon Chapman, who was the lead author of the paper, said while there had been 13 mass killings - defined as five or more victims - between 1979 and 1996, there had been none since.

"But far more significant in terms of lives that are lost are the day-to-day, very unspectacular killings where an individual shoots another individual or maybe two, and by far and away the biggest category of gun deaths are suicides," Professor Chapman said.

"We showed that if you put those killings together, they were going down before the Port Arthur massacre but they went down even faster after the law reforms and that's a really big story."

Then Prime Minister John Howard introduced gun law reform following the murder of 35 people in Port Arthur, Tasmania, in 1996. They included a ban on rapid-fire long guns and the compulsory buyback of prohibited weapons.

The researchers compared rates of intentional deaths in the 17 years prior to the 1996 laws to the 17 years afterwards, building on research they did at the 10-year anniversary.

Total suicides, including those involving firearms, increased by a mean 1 per cent per year before 1996, and then decreased by a mean 1.5 per cent per year after the gun laws were introduced.

Homicides and suicides that did not involve firearms were increasing by 2.1 per cent per year before gun reform, but the trend reversed and they began to decline by 1.4 per cent per year thereafter.

The report said this could be explained by a change towards the use of less fatal methods of suicide, improved trauma care in hospitals and quicker emergency responses because more people had mobile phones.

But it warned that the study was observational in nature and did not prove that the change in firearm deaths were attributable to the gun laws, particularly because the decline in total non-firearm suicide and homicide deaths was of a greater magnitude than gun deaths.

The study has attracted interest in the United States following the worst mass killing in American history in Orlando, Florida, and a new round of soul-searching on gun control.

The firearm homicide rate is 23 times higher in the United States than it is in Australia and the number of people killed in mass shootings with assault weapons or pistols with large-capacity magazines has increased threefold in the last 12 years.

But co-author Philip Alpers said the United States would not be able to follow the path of Australia, given the cultural and political differences between the countries.

"No matter which way you cut it, what John Howard did was confiscate private property under threat of a jail term and that's not something that would go down well in the United States," Associate Professor Alpers said.

The day after presidential nominee Hillary Clinton voiced her admiration for Australian gun laws in comments on the Orlando shootings, the first question at a press conference was whether she would confiscate guns - and the hasty reply was 'No'.

"John Howard had the support of all the parties within 12 days, he had 90 per cent support in polling and it was the single most popular thing he did as Prime Minister," Associate Professor Alpers said.

"I was in the United States when Columbine happened and we thought that would be the tipping point and then there was Virginia Tech and then there was Sandy Hook and now there's Orlando. I think it's likely to get worse in the United States before it gets better and that's tremendously sad for Americans."

Lifeline: 13 11 14

Beyond Blue: 1300 22 4636