(CNN) The number of suicides in the United States has been on the rise since 1999 in everyone between the ages of 10 and 74, according to a new report by the Centers for Disease Control and Prevention.

Researchers at the CDC's National Center for Health Statistics looked at data on cause of death for Americans 10 and older from 1999 to 2014. They also included information on age and race from death certificates.

In 2014, 13 people out of every 100,000 took their own lives, compared with 10.5 per 100,000 in 1999. The suicide rate increased every year from 1999 to 2014 among both women and men and in every age group except those 75 and older.

"The increase is broad-based," said Sally C. Curtin, a statistician at the National Center for Health Statistics and lead author of the new report , which was released Thursday.

Such an increase in suicides could also make prevention efforts more difficult. "If it were just one particular group, you could say 'that is where we need to focus,' " Curtin said.

The report is the first since 1999 to look at suicide rates among all age groups, she said.

The number of suicides increased among all racial groups except for black males, who saw an 8% decline in suicide rate from 10.5 to 9.7 per 100,000 between 1999 and 2014, respectively. The largest increases were among American Indians and Alaska Natives; in this group, the suicide rate climbed by 89% among women and 38% among men. Suicide rates among white women and white men increased by 60% and 28%, respectively.

Although it is difficult to know why suicide rates increased so much among American Indians and Alaska Natives, "they are typically in a lower socioeconomic status than some of the other ethnic and racial groups, and may have greater access to lethal means and be at higher risk of substance use and alcohol use," said Kristin Holland, a behavioral scientist in the CDC's Division of Violence Prevention who was not involved in the current research.

The suicide rate in 2014 marks a return to 1996, when the rate was also 13 per 100,000. Although the rate fell between 1996 and 1999, it has been steadily increasing since. The pace of increase has also picked up; whereas the suicide rate climbed by about 1% each year between 1999 and 2006, it increased by 2% each year between 2006 and 2014.

"We are absolutely very concerned that ... suicide is still on the rise," said Dr. Christine Moutier, chief medical officer of the American Foundation for Suicide Prevention, a nonprofit organization that funds suicide research.

"Our nation has not made the level of investment on a federal level that can have the positive effect on suicide that has happened for the other leading causes of death," such as heart disease and cancer, said Moutier, who was not involved in the current report. Suicide is the 10th leading cause of death in the United States.

The reasons for the increase in the suicide rate over the past 15 years are many and complex. Whereas there was a big push between the late 1980s and 1990s for health care providers to identify and treat depression and other mental health problems, some of this progress was undone in recent years because of concerns that antidepressants could increase suicide risk, Moutier said. These concerns were driven by controversy around the Food and Drug Administration's decision to give these medications a black box warning about the suicide risk in children, she added.

The FDA cautioned at the time that children should still be treated for depression but monitored for any signs of suicidal thoughts.

Another contributor to the rise in suicide rates could be the growing number of overdose deaths from opiate painkillers , which are considered suicide if a medical examiner or coroner determines that they were probably intentional, Moutier said. "Access to lethal means is one of the most significant risk factors for an individual to die by suicide," she added.

Yet another factor could have been the economic downturn in the late 2000s, Holland said.

Largest increases in middle-aged and young women

The report found that men died by suicide more often than women. In 2014, the rate was 20.7 suicides per 100,000 men, compared with 5.8 per 100,000 women. However, there was a 45% increase in the suicide rate in women between 1999 and 2014, whereas the increase among men during that period was 16%.

The increase in suicide deaths was greater in magnitude for women of all ages compared with men, with the exception of people 75 and older, whose suicide rate fell from 4.5 per 100,000 in 1999 to 4 in 2014.

Among women ages 10 to 14, the suicide rate increased threefold between 1999 and 2014, from 0.5 to 1.5 per 100,000. Although the rate was higher overall among men in this age group, it did not increase as much during this period, climbing from 1.9 to 2.6 per 100,000.

This increase among young women could be misleading because the rate itself is "exceedingly low," and only a small number of suicide deaths would be enough to drive it up substantially, Moutier said. "But we certainly have our eye on it," she added.

Middle-aged women, between 45 and 64, had the highest suicide rate among women in both 1999 and 2014. This age group also had the largest increase in suicide rate: 63%, from 6 to 9.8 per 100,000. The 45-64 age group also had the largest increase in suicide rate among men: 43%, from 20.8 to 29.7 per 100,000.

Men 75 and older had the highest overall suicide rate, even though it decreased from 42.4 to 38.8 per 100,000 between 1999 and 2014. The total number of suicide deaths was much greater in middle-aged men than this older group because the population of middle-aged men is so much larger, Curtin said.

A shift in methods of suicide

In both 1999 and 2014, firearms were the most common method by which men took their own lives, although the proportion of all suicides in men that were firearm-related decreased from 61.7% to 55.4%. Among women, poisoning was the most common method in 2014 and accounted for 34.1% of suicides, down from 36% in 1999.

Despite the decreases in the proportion of suicides related to firearms and poisonings, these methods are still responsible for the largest number of suicide deaths, Curtin said. And at the same time these deaths have decreased, the rate of suffocation-related suicide, primarily hanging, has increased, from 16.3% to 26% among women and from 19.1% to 26.8% among men.

"While it is good that rates for firearm- and poisoning-related suicides are decreasing a bit, it is concerning that the rates of suffocation are increasing," Holland said.

Progress toward preventing suicide

The fact that suicide rates are increasing among nearly all age groups means that prevention efforts have to be developed for many different settings, Moutier said. More research is needed to determine which factors are putting middle-aged men and women at greatest risk and which of those factors can be targeted and by which groups, she added.

The CDC is focusing its suicide prevention efforts on finding strategies that can help prevent suicide among middle-aged men because the number of suicide deaths in that group is so high.

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"They are a hard group to reach. They do not see health care providers as much as other age groups," Holland said.

She and her colleagues are testing strategies that combine improving mental health care and increasing screening for mental health problems with programs that promote social connectedness.

Moutier said she hopes efforts by the American Foundation for Suicide Prevention could be helping to lower suicide rates among people 75 and older. These efforts include educating primary-care doctors, especially those specializing in the elderly, about identifying people at risk of suicide and working to enhance their connections in society and participation in activities.