Why did Cheslie Kryst, a former Miss USA with law degree, an MBA and an on-camera gig on “Extra,” a celebrity TV show, leap to her death from a posh Manhattan apartment? As the cliche goes, she had everything to live for.

We’ve heard much about suicides as deaths of despair, with “despair” often defined as drug addictions, job losses and falling income. As far as we know, Kryst did not suffer those afflictions. But then again, neither did fashion powerhouse Kate Spade or celebrity chef Anthony Bourdain, both of whom took their lives.

Despair comes in many forms. Trying to suggest a reason for Kryst’s suicide, The New York Daily News landed on the anguish she apparently felt at getting older, a special concern for women who rely on their looks for approbation.

Kryst was 30, perhaps a time when a woman starts aging out of the young-beauty label. But what about her law degree? Lawyers in their 30s are building careers.

For we who can’t imagine turning 30 as a cause for despair, much less a reason to die, it may be illuminating to read Kryst’s astounding words in a recent essay for Allure magazine.

“A grinning, crinkly-eyed glance at my achievements thus far makes me giddy about laying the groundwork for more,” she wrote, “but turning 30 feels like a cold reminder that I’m running out of time to matter in society’s eyes — and it’s infuriating.”

Also, “Society has never been kind to those growing old, especially women.”

Though by any standard of beauty, Kryst was still one, it’s hard to deny that women getting older don’t lose visibility that men of the same age retain. But that all-purpose villain, society, has no army. It is pretty much in people’s heads.

We must look at the nature of suicide. Kay Redfield Jamison, an authority on mood disorders, cites mental illness, especially untreated depression, as the most important risk factor for suicide. Downplaying the role of external problems, she quoted a suicide note written in 1931 by a very successful artist, Ralph Barton.

“I have had few real difficulties,” he wrote, and “more than my share of affection and appreciation.” He said “melancholy” rather than problems in his life were his torment and that people looking elsewhere would have been mistaken.

Suicide attempts are often impulsive, caused by passing crises, experts on the subject say. And that’s why suicide rates among owners of handguns are especially high. The death is quick and certain. There’s no calling 911 when someone administering a drug overdose has second thoughts.

Marilyn Monroe was another case of a troubled woman who banked on physical attraction. Monroe was 36 when she probably intended to kill herself from an overdose of barbiturates. The Hollywood bombshell was found dead with a phone in her hand, leading police to speculate that she was trying to call for help at the time.

It is notable that Kryst did have other things going for her at the time. She had worked on reforming the American justice system. She did free legal work for prisoners believed to have been sentenced unjustly. And she produced a fashion blog, which enabled her to shine behind a keyboard instead of in front of a camera.

Jumping from a window does not allow for a change of mind, which made Kryst’s death extra tragic. Intervention by a mental health professional might have reversed the deep emotional dive that pushed her to self-destruction.

That’s the case among so many others suffering mental anguish, who, unlike Kryst, didn’t have the financial resources to obtain help. How terribly heartbreaking that Kryst had no one there to pull her from the edge.