Many parents find the possibility that their child might commit suicide unthinkable - so unthinkable they might not be prepared to try to stop it from happening.

That is a mistake, according to experts. To prevent tragedy, parents should be on guard for an array of warning signs.

"Suicide is vastly complex," said American Foundation for Suicide Prevention vice-president of research Jill Harkavy-Friedman. "There is not one cause of suicide. There are many factors that come together."

The list of things to watch for is different for each child.

First, there are the risk factors: abuse, head trauma, chronic pain, addiction, mental illness and a family history of mental illness or suicide. Ninety per cent of people who commit suicide have a diagnosable mental health condition, Dr Harkavy-Friedman said.

Then there are a host of factors even conscientious parents might not pick up on. The world of children is, of course, partly hidden from adults, who can miss bullying on social media or in the playground.

A stray comment that might be dismissed as part of a phase - "You'd be better off if I wasn't here anyway" - might be a cry for help. Even eating too much or too little could signal a deeper problem that demands attention.

Talking is the first line of defence. The days of doctors advising not to use the word "suicide" are over, said Dr Harkavy-Friedman.

"If people are suicidal, they are suicidal," she said. "You are not going to make them that way... (but) you can decrease the pressure."

Early intervention is key.

Dr Jane Pearson, head of the National Institute of Mental Health's suicide resource consortium, said people who are suicidal have "very constricted thinking". It is easier to help them if they have not yet decided how and when to end it all.

Experts also say parents should talk to other parents, teachers and trusted adults about what children are saying about one another.

"We know from years of research kids are more likely to talk to other kids than they are to talk to an adult about this," Dr Pearson said.

Tools unknown a generation ago - for example, medication and social media, which can lift people up as much as it can bring them down - offer hope.

"We now have therapies and interventions in ways we did not have before," said Dr Pearson. "I am very hopeful we can bend that curve down."

WASHINGTON POST