The Centers for Disease Control and Prevention have released a new report on youth suicide, and the results are shocking. In just an eight-year period from 2007 to 2015, the suicide rate for teen girls between the ages of 15 and 19 have doubled, and authorities aren’t really sure why that is.

The new rate of 5.1 suicides per 100,000 people represents a 40-year high. In 1975, the rate was 2.9, and it increased to 3.7 in 1990 before dropping to 2.4 in 2007. But for some reason, the numbers have suddenly risen. And boys that age haven’t fared well either, seeing their suicide rate jump by more than 30 percent, from 10.8 to 14.2 per 10,000 individuals.

“These data show that between 2007 and 2015, there’s substantial increases in suicide rates for both young males and young females,” said Tom Simon, an author of the report and associate director for science in the division of violence protection at the CDC, according to a CNN report. “For young males, there was a 31% increase in suicide rates, and for young females, the suicide rate doubled.”

CDC statistics indicate that there were 1,289 suicides among young males in 1975 in the United States. For girls 15 to 19 that year, there were 305 suicides, and in 2015, that figure is 1,537 for males and 524 for females between 15-19.

“Suicide is a serious public health problem that can have lasting harmful effects on individuals, families, and communities,’ the CDC states. “While its causes are complex and determined by multiple factors, the goal of suicide prevention is simple: Reduce factors that increase risk (i.e. risk factors) and increase factors that promote resilience (i.e. protective factors). Ideally, prevention addresses all levels of influence: individual, relationship, community, and societal. Effective prevention strategies are needed to promote awareness of suicide and encourage a commitment to social change.”