Many parents find the possibility 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 Jill Harkavy-Friedman, vice president of research for the American Foundation for Suicide Prevention. “There’s 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 percent of people who commit suicide have a diagnosable mental health condition, 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 on 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 defense. The days of doctors advising not to use the word “suicide” are over, Harkavy-Friedman said.

“If people are suicidal, they’re suicidal,” she said. “You’re not going to make them that way … [but] you can decrease the pressure.”

Early intervention is key. People who are suicidal have “very constricted thinking,” said Jane Pearson, head of the National Institute of Mental Health’s suicide resource consortium. 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 each other.

“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,” 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 didn’t have before,” Pearson said. “I’m very hopeful we can bend that curve down.”

In the District, officials are trying to expand a program offered in 60 schools, starting in the third grade, that tries to identify children who are contemplating suicide, according to Tanya A. Royster, director for the D.C. Department of Behavioral Health. Anyone in need of emergency mental health care also can contact the city’s helpline, 1-888-7WE-HELP.

To reach the National Suicide Prevention Lifeline, call 1-800-273-TALK (8255). You can also text a crisis counselor by messaging 741741.