A close friend of one of my colleagues committed suicide last week. It happened as so many suicides do—out of the blue. A few days earlier, my colleague had spent the day hanging out with her friend, who was relaxed, upbeat, and normal.

Sadly, that’s not uncommon. “Many people who commit suicide do so without letting on they are thinking about it or planning it,” says Dr. Michael Miller, assistant professor of psychiatry at Harvard Medical School.

More than 100 Americans commit suicide every day. It’s the tenth leading cause of death overall; third among 15- to 24-year-olds and fourth among 25- to 44-year-olds.

Although some people who commit suicide have an identifiable mental health problem, like depression or addiction, others don’t. Some talk about wanting or planning to kill themselves or give other hints, others don’t. As my colleague Annmarie Dadoly wrote in this blog last year, many suicides are impulsive acts, with the decision to do it being made just minutes or hours before that act.

What prompts a person to take his or her life? No one really knows—experts never get to talk to people who have committed suicide. They can only talk to those who are contemplating suicide or who survive it. By definition, that is a different group.

Every suicide, like every person, is different. Many are sparked by intense feelings of anger, despair, hopelessness, or panic. Things that can put an individual at a higher risk for suicide in the short term include:

• an episode of depression, psychosis, or anxiety
• a significant loss, such as the death of a partner or the loss of a job
• a personal crisis or life stress, especially one that increases a sense of isolation or leads to a loss of self-esteem, such as a breakup or divorce
• loss of social support, for example, because of a move or when a close friend relocates
• an illness or medication that triggers a change in mood
• exposure to the suicidal behaviors of others, such as friends, peers, or celebrities.

We all face crises or problems like these. One difference is that among individuals who take their own lives, these situations cause such pain or hopelessness they can’t see any other way out.

No warnings

Suicide almost always raises anguished questions among family members and friends left behind: What did I miss? What could I have done? In my friend’s case, the answers are nothing and nothing.

“Many people never let on what they are feeling or planning. The paradox is that the people who are most intent on committing suicide know that they have to keep their plans to themselves if they are to carry out the act,” says Dr. Miller. “Thus, the people most in need of help may be the toughest to save.”

Some suicides (and suicide attempts), though, don’t come completely out of the blue. Some people — including those who are more ambivalent about suicide — consciously or unconsciously drop hints. Here are a few behaviors that may put friends and family on notice that the risk of suicide is on the rise (adapted from HelpGuide.org):

• Talking about suicide: Statements like “I’d be better off dead” or “If I see you again…,”
• Seeking the means: Trying to get access to guns, pills, or other objects that could be used in a suicide attempt.
• No hope for the future: Feelings of helplessness, hopelessness, and being trapped, or believing that things will never get better.
• Self-loathing: Feelings of worthlessness, guilt, shame, and self-hatred.
• Getting affairs in order: Giving away prized possessions or making arrangements for family members.
• Saying goodbye: Unusual or unexpected visits or calls to family and friends; saying goodbye to people as if they won’t be seen again.

People who exhibit these signs are often communicating their distress, hoping to get a response. This is very useful information that shouldn’t be ignored.

If you think a loved one or friend might hurt himself or herself, call the National Suicide Prevention Lifeline at 800-273-TALK. Counselors are available 24 hours a day, 7 days a week. The service is available to anyone. All calls are confidential.

But when individuals suddenly take their own lives with no warning, all we can do is look to each other for support. It may be natural to ask, “What did I miss?” But we should remind ourselves what experts say: This kind of death defies prediction. (The American Association of Suicidology offers helpful resources for survivors of those who committed suicide.)