The rate of suicides in the US has gone up over the past 15 years — for almost everyone. The percentage of overall deaths attributable to suicide was 24 percent higher in 2014 than it was in 1999 for everyone under the age of 75, according to a new study by the CDC’s National Center for Health Statistics.

Some of the biggest increases in suicide rates occurred among women

While more men than women died by suicide in 2014 — more than 33,000 men compared to around 9,600 women — some of the biggest increases in suicide rates occurred among women. Men now die 3.5 times more often from suicide than women, but that’s narrowed from 4.5 times in 1999. And that’s despite the suicide rate increasing among men as well.

The numbers, gathered from the CDC's data on causes of death for 1999 and 2014, speak to a larger mental health issue beyond suicide, argues study author Sally Curtin, a statistician at the National Center for Health Statistics. "Percentage wise, some groups had more [increases] than others, but the rise was broad-based." And this study may not show the true size of the phenomenon — it only looked at suicide deaths, not attempts. "Obviously, the public health issue of suicide is a lot bigger than the death," said Curtin. "For every death you have a lot more attempts and hospitalizations." That’s not the only limitation, either — many suicide deaths may have been misclassified as something else.

The women most at risk, the data showed, were ages 45 to 64; their risk of suicide almost doubled since 1999. Additionally, the rate for girls between ages 10 and 14 more than tripled between the two years. "The rate is quite low for the youngest, but it was the biggest increase," said Curtin.

The study authors didn’t say why more people are dying by suicide, and some experts say there isn't enough research yet to explain the changes. "The very short answer is we don't know, and frankly I'm not sure anybody knows at this stage in the game," said Joel Dvoskin, a behavioral health and wellness expert at the University of Arizona who was not involved in the study. However, Dvoskin said that this study may help to inspire more research focusing on what may be causing the increasing suicide rates. "It's good to see it being studied," he said. "If you're going to fix a problem, the first thing you have to do is identify it."

Dvoskin also hopes the research will place more emphasis on suicide prevention in the US. "A focused and targeted suicide prevention effort in the general population would likely be successful," he says.