The rate increased by about one per cent a year from 1999, then accelerated to two per cent annually from 2006 to 2014, said the findings by the Centers for Disease Control and Prevention's National Center for Health Statistics.
The rise was seen among both males and females and for all ages 10-74, said the report.
The biggest jump was among girls aged 10-14, whose suicide rate tripled from 0.5 per 100,000 people in 1999 to 1.5 per 100,000 in 2014.
"We are seeing younger and younger kids dying by suicide," said Victor Fornari, director of the division of child and adolescent psychiatry at Zucker Hillside Hospital in Glen Oaks, New York.
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This is "really a worry," added Fornari, who was not involved in the study.
"I think it may be a reflection of access to social media, Internet and cyber bullying, and youth are hurried. They are being exposed to things sooner than they would have been," he told AFP.
In 1999, 1.9 per 100,000 people in this age group committed suicide, and by 2014 the number had risen to 2.6 per 100,000, a 37 per cent increase.
Among men, those over age 75 were most likely to kill themselves in both 1999 and 2014.
However, in contrast to other age groups, elderly men's suicide rate decreased by eight percent over the 15 years studied, going from 42.4 per 100,000 in 1999 to 38.8 in 2014, the report said.
Among women, suicide rates were highest for those aged 45-64 in both 1999 (6.0 per 100,000) and 2014 (9.8), said the report.
"This age group also had the second-largest per cent increase -- 63 per cent -- since 1999."
The study pointed to a narrowing of the suicide gender gap over the years, largely due to a 46 per cent increase in female suicides.