Suicides that involve guns are fatal nine times out of 10, a new study reveals.

Researchers at Harvard University found that while firearms are used in the least number of suicidal acts, they result in far and away more deaths.

Suicide has climbed the ranks of causes of death in the US to be come the 10th leading cause of fatalities among adults in the US, trailing just behind kidney diseases.

The study authors found that the use of a gun was the main predictor of variation in rates of suicide across the nation.

Guns are used in less than 10 percent of suicide attempts, but they lead to deaths almost 90 percent of the time they're used, a staggering Harvard study reveals

There are more guns than people in the US.

It's an often cited statistic, but a growing body of research points to the correspondence between firearm availability and suicide rates.

And that discovery comes as rates of suicide march ever-higher.

In 2017, 47,173 Americans died by suicide, according to the American Foundation for Suicide Prevention.

That number marked a 33 percent increase over suicide rates in the US in 1999.

Experts warn that access to a means of suicide is one the most significant predictive factors for death by suicide.

But not all means are equally lethal.

To work out which methods of suicide put Americans at greatest risks of dying by suicide, the Harvard team analyzed data gathered by the National Vital Statistics System on 309,377 suicide deaths.

They compared this data to records from nearly 1.8 million hospital admissions for suicide attempts.

Suicide's fatality rates varied based on a number of factors.

Older people's suicide attempts were much more fatal than those of their younger counterparts. Those over 65 were at more than three-fold greater risks of dying by suicide than were those between the ages of 15 and 24.

For men, suicide proved fatal much more often. Nearly 15 percent of men who attempted suicide lost their lives, compared to 3.3 percent of women.

No matter what means they used, men were more likely to die by suicide, but the method was highly predictive of the fatality rate.

The majority of suicide attempts - nearly 60 percent - were by self-poisoning, including intentional attempted drug overdoses.

But only 13.5 percent of those ultimately proved fatal.

Combined, hangings and gunshot wounds accounted for the vast majority of suicide deaths: 75.3 percent.

But they made up only 8.8 percent of all attempts.

Separated out from hangings, the fatality rate for gun deaths is staggering.

Firearm attempts were fatal 89.6 percent of the time.

Preventing suicide, alongside other deaths of despair, is a high priority for US public health officials, and this isn't the first study to suggest that gun availability is strongly linked to suicide deaths.

A Boston University team found that every 10 percent increase in the number of guns owned by a household was linked to a 25 percent increase in the number of people between ages 10 and 19 who died by suicide.

Yet the CDC's hands are tied when it comes to gun research, due to a 1996 law that forbids it from funding studies to 'advocate or promote gun control.'