Once upon a time, Jessica Vadino listened to the Wonder Woman audiobook cassette "Cheetah on the Prowl" as she fell asleep, snug as a bug in a bunk bed.

Now, Vadino is 39, and, more than ever, as she juggles a job, a divorce, and new digs in Old City, the digital techie struggles to catch her zzzs. "My brain runs a million miles a minute," she says on this Wednesday night as bedtime nears. "I work under really high pressure. I'm always thinking. I'm always on."

What's an adult to do to turn off? Why, listen to a bedtime story, of course. Vadino climbs into her king-size bed, taps the Calm app on her iPhone, and selects from Sleep Stories. Then, to a measured, monotone voice describing a trans-Siberian railroad journey — subtle sounds of a train chugging in the background included — she pulls up the gray comforter and falls asleep, usually within five minutes. Vadino says the experience reminds her of childhood, of the comforting Wonder Woman tape, and of the stories her parents read to her and her sister at bedtime.

"This is how I sleep," she says, adding that she gets five to seven hours a night. "It helps me decompress and stop trying to figure out a solution to whatever next problem is out there."

The sweet-dreams ritual once reserved for the wee lot is all grown up. In a 24/7, never-off world of glowing screens, cable news, and tweets, posts, texts ad nauseum, more adults are searching for a way to wind down — and none more so than at bedtime. According to the American Academy of Sleep Medicine, sleep is a scarce commodity for the one-third of Americans who complain about insomnia, which included trouble falling or staying asleep at times. Polls put the number even higher among 21- to 35-year-olds.

For many insomniacs, it turns out the solution may be a sort-of-good story. If it's too riveting, it defeats its purpose.

The nostalgia for the childhood ritual echoes the popularity of adult coloring books as stress reducers. Bedtime stories join other trendy slow-down pursuits, such as meditation, slow food, and slow TV, which is hours of slow-paced coverage of an ordinary event.

This month, Calm debuted an eight-hour sleeper of a film called Baa Baa Land. It features sheep in the English countryside doing what sheep do, which is not much. A trailer proudly proclaims it the "dullest movie ever made."

Add in anti-energy drinks (Tranquini, Just Chill, Tyme Out), performance sleepwear, and nap bars that offer siesta space by the minute, and the Land of Nod never looked so attractive.

Bedtime stories, says Emily Anatole, are unfolding as the next big thing to get some much-needed rest. "We foresee books, podcasts, and other forms of narratives that aid in sleep rising in popularity," says the associate insights director for trend forecasting firm Cassandra. She calls it part of the boom in "calming content."

Calm started as a meditation app. According to co-CEO Michael Acton Smith, the company's data showed a spike in app use around bedtime. Turns out meditation, which focuses attention, is not the ideal way to get sleepy. Instead, Calm launched 40-winks-inducing content late last year. "We thought, 'Let's keep it simple, and do what we did as children, which was have bedtime stories read to us.' "

Besides the trans-Siberian tale, Sleep Stories offers 49 other choices at what Smith says is the optimal length of 24 minutes. All but four are targeted at adults. One of his favorites is "Blue Gold," set in the lavender fields of Provence. It pairs well with a new company product, Sleep Mist, a lavender scent to spray on the pillows of sleep seekers. Next up? Adult lullabies, Smith says.

"There's something beautiful, soothing, nurturing, nourishing about hearing a voice read to you as you fall asleep," he says. "Why should that stop now that we're grown-ups?"

It shouldn't, says Sigrid Veasey, a doctor of sleep medicine at the Perelman School of Medicine at the University of Pennsylvania. "I think it's a wonderful thing," she says.

Ritual, she says, is a fundamental of a good night's sleep of about 7½ to 8½ hours a night for adults. "All of the things we know we should be doing with children, the bedtime bath, getting into nice, comfy jammies, and sitting down and reading bedtime stories is a tried-and-true method … that works," Veasey says. "It certainly can work for grown-ups, too."

The podcast "Sleep With Me" has a faithful following; it gets more than 3 million downloads a month across its 500 episodes. Though it began in 2013, creator Drew Ackerman says his inbox exploded after the 2016 election. Apparently, some folks were super-stressed.

"I call it a sleep offering, rather than a sleep solution," says the librarian by day and insomniac by night who goes by Dearest Scooter. Let's just say the nickname fits the goofy image he cultivates. "It's not a should. People already have enough anxiety."

Ackerman takes a monotone, meandering approach, going on tangents, and tangents of tangents, in that gravelly voice of his. It all makes for an often-nonsensical but humorous (say his fans) story. His tagline is "a lulling, droning, boring bedtime story to distract your racing mind." (He doesn't use it himself, however, because as his own worst critic, it keeps him awake.) Typically, Ackerman recaps a TV show, currently "Game of Thrones," focusing on minutiae, such as misconceptions about glaciers and the word whinging, which the Hound accused Gendry of doing. Or he'll riff on whatever is trending on Twitter, except politics, which is not conducive to restfulness, he notes.

Philadelphia lawyer Veronica Williams, 31, has struggled with sleep because of anxiety for a while. When she first came across the podcast, she didn't care for it, but on second listen, she was sold. "Now, I really can't sleep without it," says Williams, who favors an original series Ackerman does about farm animals and a private eye. "It's super-comforting. It leads to good dreams."

Author and film producer Ben Holden has a theory about stories and sleep. "Bedtime storytelling verges on a primal need," he writes in the introduction to Bedtime Stories for Grown-Ups, which  came out in 2016. Besides being an ancient tradition, he notes, "storytelling doesn't stop once the lights are turned off. After all, when we dream, and vital neurological faculties are restored and repaired during REM, our brain tells itself a story."

His anthology features classics (bits from Shakespeare's The Tempest, Rip Van Winkle), poems such as "The Owl and the Pussycat," and selections from contemporary lit authors, such as Neil Gaiman and Nora Ephron.

The pieces "allow for a full stop at the end of the day," Holden says, "so you can then replenish for the next day."

In other words, bedtime stories let us sleep, if not live, happily ever after.

Contact Lini S. Kadaba at Lkadaba@gmail.com. Follow @exinkygal.