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Suicide rates among U.S. children and teens have hit startling rates and a study now finds one clear predictor of youth suicide: gun ownership.

Youth suicides rates are higher in states with high gun ownership rates, a team at Boston University School of Public Health found.

“Household gun ownership was the single biggest predictor of youth suicide rate in a state,” Dr. Michael Siegel, a public health specialist at BU, told NBC News.

Siegel has been studying the relationships between gun ownership and homicide, suicide and other factors. It’s well known that people with access to a gun are far more likely to complete suicide. And some data had suggested that gun ownership in general was associated with higher suicide rates.

But there were still gaps in the possible explanations. “Some argued that, isn’t it possible that gun households are systematically different from non-gun households? In particular, is it possible that there are just higher rates of depression and suicidal ideation in a gun household?” he said.

So Siegel and his team took state-by-state data from the Centers for Disease Control and Prevention on gun ownership from 2004. The CDC has not done a study on gun ownership by state since then.

They also examined youth suicide rates (those aged 10 to 19) between 2005 and 2015, and looked at other surveys that covered rates of depression and suicidal thinking, as well as alcohol use and other factors that might affect suicide.

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A state’s rate of gun ownership accounted for 55 percent of the differences seen from one state to another, the team found.

“For each 10 percentage-point increase in household gun ownership, the youth suicide rate increased by 26.9 percent,” they wrote in their report, published in the American Journal of Preventive Medicine.

“The only other factors that were associated with overall youth suicide rates were the suicide attempt rate and the percentage of youth who were Native American,” they added.

“Together, the model explained 92 percent of the variation in overall youth suicide rates across the 47 states.”

In Alaska, for instance, the youth suicide rate is 15.2 suicides per 100,000 people aged 19 and under. Just under 60 percent of households have guns. In South Dakota, the suicide rate is 14.9 per 100,000 and again, just under 60 percent of homes had guns in 2004.

In New York and New Jersey, the youth suicide rate is 2.7 and 2.6 per 100,000. In New York, 18.5 percent of households had guns and in New Jersey, 11.4 percent did.

“This study demonstrates that the strongest single predictor of a state’s youth suicide rate is the prevalence of household gun ownership in that state,” Siegel said.

The association was not always crystal clear. Alabama and Mississippi both had high gun ownership rates — over 50 percent — but low suicide rates. In those states the youth suicide rate was around 4.5 percent per 100,000. Siegel said culture may be a factor there. Both Alabama and Mississippi have large African-American populations. African-Americans are less likely than whites to die by suicide and are also far less likely to own guns.

Gun ownership may in fact be driving the rise in suicide rates, the researchers said.

“The availability of firearms is contributing to an increase in the actual number of suicides, not just leading youth to substitute other means of suicide for guns,” Anita Knopov, one of the researchers who led the study, said in a statement.

Siegel is not advocating for any particular action, but said states where many people own guns should be aware of the association and the risk to youth.

“Because states with high levels of household gun ownership are likely to experience higher youth suicide rates, these states should be especially concerned about implementing programs and policies to ameliorate this risk,” he said.

It would be important to know whether youth who died by suicide were accessing guns that were not locked up, he said.

The researchers said states — and parents — should take heed. “The problem of firearm suicide among youth is particularly alarming: every day, an average of three youth between ages 10 and 19 years die by firearm-related suicide,” Siegel’s team wrote.

“In 2016, there were 1,102 youth firearm suicides. Data from the National Violent Injury Statistic System demonstrated that 82 percent of firearm-related suicides among youth (aged 17 years and younger) involved a firearm owned by a household member.”

Why are guns so strongly associated with suicide?

Experts say it’s because they are quick and immediately lethal. Suffocation, pills or other methods take longer and are more likely to fail to kill.

“Firearms are 2.6 times more lethal than any other means of suicide; thus, access to firearms might be expected to contribute to a higher incidence of suicide,” the team noted.