The others include Alzheimer's disease and drug overdoses.
Middle-aged adults - age 45 to 64 - had the largest rate increase, rising to 19.2 per 100,000 in 2016 from 13.2 in 1999.
Suicide is the 10th leading cause of death in the USA and rates have been climbing steadily for years. The report showed an overall 25.4 percent increase nationally during the period, with only one state -- Nevada -- seeing a decrease in its rate.
More than half of suicides in 2015 in a subgroup of 27 states were among people with no known mental health condition, the Centers for Disease Control and Prevention found. Suicide is rarely caused by any single factor, health officials said, but information from coroners' reports suggest numerous deaths followed relationship problems, substance use and financial crises.More news: The Halloween Trailer Will Scare the Knife Out of You
Life stressors like relationship problems, substance abuse and problems with physical health conditions were also prominent factors in suicides, the CDC's data showed.
'If we step back from the statistics, mental health does not discriminate, ' said Dr Shainna Ali, a Florida psychologist. The most common method, regardless of whether a mental health disorder had been diagnosed, was firearms. I think it captures a lot of trends that we've been becoming more and more aware of over recent years", says psychologist Michael Anestis at the University of Southern Mississippi, who researches suicide and is the author of Guns and Suicide: "An American Epidemic.
The number one means to commit suicide was found to be firearms, followed by hanging, and then poisoning, including through opioids. But researchers can not say what percentage of those had severe pain as their main problem.
Nationwide, the suicide rate rose to 15.4 per 100,000 in 2014-2016, up from 12.3 in 1999-2001. It's up everywhere. And we know that the rates are actually higher than what's reported.
Opioid addiction is another factor that could have led to the increase, although experts say it is hard to differentiate intentional deaths by overdose from accidental deaths. Approximately half of such deaths involve the use of a firearm.More news: IHOP to IHOB name change 'dumbest' move ever, brand experts warn
The CDC recommends that states take a comprehensive public health approach to suicide prevention, and that everyone remain vigilant about possible warning signs.
And finally, Vermont has a lot of military veterans, and veterans as a group are twice as likely to die by suicide than the general population, Delaney said.
"Mental health conditions are often seen as the cause of suicide, but suicide is rarely caused by any single factor", the CDC reports.
Access to guns can make it more likely that an impulsive or intoxicated person will attempt suicide even if he or she has no clear mental health problem, Dr. Brent added. Rates ranged from 6.9 per 100,000 in the District of Columbia to 29.2 in Montana. Finding economic circumstances was a major contributing factor, especially during the Great Recession (2008).
Ask someone you're anxious about if they're thinking about suicide.More news: Tiger grouped with Thomas and Johnson at U.S. Open
This report contains information from the Associated Press. The National Suicide Prevention Lifeline (1-800-273-8255) provides 24/7, free, confidential support for people in distress, as well as best practices for professionals and resources to aid in prevention and crisis situations.