Roughly one in 25 US teens has attempted suicide, and one in eight has thought about it, according to a new study.

Researchers said those figures are similar to the prevalence of lifetime suicidal thinking and attempts reported by adults.

According to the US Centres for Disease Control and Prevention, suicide is the third leading cause of death for people ages 10 to 24, killing about 4,6000 young people each year.

It suggests what personal experience already tells us: the teenage years are an especially vulnerable time.

"What adults say is, the highest risk time for first starting to think about suicide is in adolescence," said Matthew Nock, a psychologist who worked on the study at Harvard.

The findings appear in the journal JAMA Psychiatry.

The results are based on in-person interviews of some 6,500 teens and questionnaires filled out by their parents.

Just over 12% of the youth had thought about suicide. Some 4% had made a suicide plan and 4% had attempted suicide.

The researchers found that nearly all the teens who thought about or attempted suicide had a psychological disorder, including depression, bipolar disorder, attention deficit hyperactivity disorder or problems with drug or alcohol abuse.

More than half of the youth were already in treatment when they reported suicidal behaviour, which Mr Nock said was both encouraging and disturbing.

The findings leave many questions unanswered.

Because most youth who think about suicide never make an actual plan or attempt, doctors need to improve how they determine which are most at risk of hurting themselves, Mr Nock said.