(Reuters Health) - Restricting access to firearms just for people with known mental health or substance abuse problems and those who previously tried to kill themselves won’t prevent many suicide deaths, U.S. researchers say.

Half of all suicide deaths in the U.S. are due to firearms. How many could be prevented by limiting firearm access for substance abusers, people with a mental health condition and people with a history of suicide attempts?

“Few,” Jennifer Boggs of Kaiser Permanente Colorado in Denver and her colleagues write in the Annals of Internal Medicine. The researchers reviewed the medical records of 2,674 adults and teenagers who died by suicide between 2000 and 2013 and had been patients of a network of health care systems participating in a suicide risk identification study.

A bit more than half, 55 percent, had a mental health or substance abuse problem and about 43 percent of those committed suicide with a firearm.

Only 11 percent had previously attempted suicide, of whom a little more than a third, committed suicide with a firearm.

Overall, 671 people with no mental health or substance abuse condition committed suicide by firearm during the study period compared with 627 who had one or both diagnoses.

Only 109 who previously attempted suicide used a firearm to kill themselves compared with 1,189 who did not.

Put another way, only about a quarter of individuals with a known mental health or substance abuse problem committed suicide by firearm, as did just 4 percent of those who had previously attempted suicide.

Based on the findings, the authors suggest that suicide prevention efforts expand beyond firearms to include people who may be thinking of using other means of suicide.

“To truly make a difference in reducing suicide rates, we need to find and help more of the people who are at risk,” Boggs told Reuters Health by email.

“Most people who die by firearm suicide haven’t sought or received care for a mental health or substance abuse condition and therefore are unlikely to be identified in advance,” she adds.

Dr. Paul Appelbaum of Columbia University College of Physicians and Surgeons in New York City told Reuters Health that all health professionals should be aware of suicidal thinking in their patients, ask about access to firearms and advise families to remove guns from the home.

That said, many suicidal people aren’t in contact with the medical system. “Even when they are, suicide is difficult to predict,” he said by email.

“Unless the overall prevalence of firearms in our society is reduced,” said Appelbaum, who was not involved in the study, “it will be difficult to prevent the use of guns in suicides.”

SOURCE: bit.ly/2fazTFW Annals of Internal Medicine, online July 3, 2017.