In the shorter term, the suicide rate for those girls doubled between 2007 and 2015, the research indicates.
By comparison, the 2015 suicide rate for boys in this age group was lower than in the peak years of the mid-1980s through the mid-1990s. The researchers derived suicide rates from official data from death certificates.
"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 US Centers for Disease Control and Prevention, which published the new data Thursday.
"For young males, there was a 31% increase in suicide rates, and for young females, the suicide rate doubled," Simon said.
Specifically, the suicide rate for males between 15 and 19 increased from 12 per 100,000 population in 1975 to 18.1 per 100,000 in 1990. It then declined to 10.8 per 100,000 by 2007 and then increased again to 14.2 per 100,000 by 2015.
Among females, the suicide rate increased from 2.9 per 100,000 in 1975 to 3.7 per 100,000 in 1990, dipped to 2.4 per 100,000 in 2007 and then spiked to 5.1 per 100,000 in 2015.
"We know that overall in the US, we're seeing increases in suicide rates across all age groups," Simon said, putting the new report in perspective.
"We're not seeing the same kind of increases among the oldest adults, but we are seeing substantial and sustained increases now for the other age groups really going back to 2000," he said, adding that the the pattern is "pretty robust."
Carl Tishler, an adjunct associate professor of psychology and psychiatry at the Ohio State University who was not involved in the report, said the high suicide rates among older teens in 2015 "could be the result of a lot of things."
"Some of the opiate or heroin overdoses in adolescents may be interpreted by emergency departments as suicides. There may be more Internet suicides," Tishler said.
Simon said it's "unlikely" that increases in suicide rates are due to any single factor. Possible risk factors for suicide include a history of substance abuse, exposure to violence, social isolation, conflict within relationships, stigma and a lack of available support.
Simon suggested that the lingering effects of the Great Recession in the late 2000s may have contributed to stress within families, causing anxiety in teens.
"In times of economic prosperity, suicide rates go down," he said. "In times of economic instability, suicide rates go up."
Social media can have either negative or positive effects, Simon said. Cyberbullying and harmful content might push a vulnerable teen toward self-harm, yet "social media can help increase connections between people, and it's an opportunity to correct myths about suicide and to allow people to access prevention resources and materials."
Dorian A. Lamis, an assistant professor in the department of psychiatry and behavioral sciences at Emory University School of Medicine/Grady Health System, theorized that use of social media and cyberbullying may affect teenage girls more than boys, resulting in rising suicide deaths among older teen girls.
"Some research has suggested that the timing of puberty in girls is a contributing factor for the increased suicide rate," said Lamis, who was not involved in the new research. Puberty starts as early as 8 in some girls. The psychosocial and physical changes may leave girls "vulnerable to depression, anxiety and other psychiatric disorders earlier on in life." These known risk factors for suicide may catch up with a girl as she grows older.
Tishler noted that previous studies
from the CDC have indicated that males take their own lives at nearly four times the rate of females and thus represent 77.9% of all suicides. Yet females are more likely than males to have suicidal thoughts.
"If you look at suicide attempts by girls, it's typically that girls attempt suicide about four to one or three to one over boys, yet boys complete suicide in the reverse," Tishler said. "That tends, we think, to have to do with the modality of suicide attempt."
Simon noted that in this older teen age group, the primary method chosen by boys is firearms, yet for girls, the most common method is suffocation. Still, a significant number of females may choose to poison themselves with an overdose
, which can be remediated in an ER in some cases, Tishler said.
He theorized that girls now have access to pills that may be more lethal -- or more quickly lethal -- than those available to girls in the past, and this may have contributed to the rising rate of suicide deaths among teen girls. Similarly, Lamis conjectured that girls may have access to "more lethal methods in their suicide attempts, resulting in an increased number of deaths."
The new report also does not indicate how many of the teens who completed suicide were in treatment with a medical health professional and how many were receiving medication for depression or other mental illness, Tishler said. He added that he's convinced that the quickness to start or change these medications, which are categorized as psychotropic, "is done in such a manner that makes people more vulnerable to attempting suicide."
"Physicians need to be careful" when increasing, starting or stopping psychotropic medications, because this may "give someone energy to die by suicide," Tishler said.
One symptom of depression can be psychomotor retardation, which medication reduces, helping people become more active. They may attempt more activities to do better in school or to be more social. The medicines may give depressed teens more energy to plan and follow through with a suicide attempt or die by suicide. Psychotropic drugs
also can change mental status and in some cases may increase suicidal thoughts, which is why some of them come with warnings.
"The message for parents, teachers, coaches and religious leaders is to not be afraid to talk to a young person when they are concerned," Simon said. He added that anyone contemplating suicide or concerned for another should reach out to the National Suicide Prevention Lifeline