It’s early August and I’m in southwestern Montana, watching the service bars on my phone go dark as I drive south along the Bitterroot River from Missoula and towards the river’s lesser-visited West Fork. The state’s notoriously big sky is beaming, its wild trout beckoning.

I use my last mile of phone signal to call an editor at his office in New York. We discuss details of a work project that’s about to go out the door, and then I inform him that I’ll be unreachable for the next 48 hours or so. I’m trying to sound neutral, almost apologetic, which is the opposite of how I actually feel. I feel amazing.

It’s a funny thing, the uneven emotional arc that my fishing trips usually follow. During the hours leading up to my time on the river, I throb with giddiness. Once out there, the strike of a fish brings pangs of surprise and delight. Hooking and landing one generates a blast of elation, sometimes one that I’ll pass along verbally to the skies myself, if the excessive joy I’m feeling demands it.

But most of the time I spend on the water is nothing like this. It consists of near-misses, mini-tantrums, moments of head-scratching confusion and long stretches of, well, nothing much; a nothing so enveloping that sometimes I don’t notice the day has passed until the encroaching darkness has made it suddenly difficult to manage the hair-thin tippet of my fly line.

That first day on the Bitterroot, around noon, I tumbled in over my waders while trying to ford a deep section, dried out, waded in again, and managed to land a radiant 18in cutthroat, the native trout of the Rocky Mountains. Back at the campground afterwards, I struck up a conversation with an angler named Tim. I judged him to be in his early sixties, and he strolled to the bear-proof garbage bin with the contented air of someone who’d also had a good day of fishing. We talked about the reasons people take up this peculiar sport, a line of inquiry that happened to interest Tim very much. He was not only a lifelong fly-fisherman, but also a trained psychologist, and had interviewed so many people on the subject of why they fish that he’d been thinking about publishing a book about it.

The moment for a book like that seems ripe. Just a few months ago, The New York Times ran a trend piece on fly-fishing, focusing on outdoorsy Instagrammers who have taken to it and caused a spike in interest. The contemplative and individualistic nature of the sport has always been part of its appeal, but amid digital overload and the rise of mainstream mindfulness, the idea that fly-fishing is good for you seems more credible than ever.

At some point, scientists will be able to tell us more. For now, the fishing-as-wellness argument enjoys the backing of Dr Herbert Benson, the Harvard pioneer of mind-body medicine, who has verbalised what any angler acquainted with the Zendō or the Headspace app probably knows already: that the simple, repeated task of casting a featherweight fly into the water and watching it be swept through the current is a lot like meditating.

My new friend, Tim – Dr Tim Berry, who lives outside of Missoula and also takes his executive-coaching clients out on the river – agrees. He considers fishing that is undertaken in the right frame of mind to be a form of “informal meditation”, he told me recently on the phone. He even recommends it to angler patients suffering from anxiety or depression. “The tasks of wading, casting, positioning the fly – I use these as a practical way of teaching people to be more fluid, and then to apply this to their professional and personal lives as well,” he says.

This is advice that men especially can use. Guides I’ve spoken to confirm that men, especially those wealthy enough to regularly engage them, are likely to do too much muscling and not enough listening on the river. Competing with the river, in other words, and with their fellow fisherman; one reason I don’t mind spending at least half my fishing days alone. But fishing also foments closeness between men, explaining why so many father-son vacations revolve around it. Mr Jeremy Charles, a chef who’s been described as Canada’s answer to Mr Francis Mallmann, says he likes nothing better than taking his eight-year-old son out near their home in St. John’s, Newfoundland, where Mr Charles runs the acclaimed restaurants Raymond’s and Merchant Tavern.

I met him last June at a deluxe fly-in lodge in Labrador called Rifflin’ Hitch, where he was eager to be the first guest of the season to catch an Atlantic salmon. “In my life, at least, nothing but good has come from fly-fishing. I feel bad for my friends who don’t do it,” Mr Charles told me later. He has been casting since he could walk and embodies the conservationist ethos of most of today’s fly-anglers. Though he keeps trout and Arctic char, both of which are abundant in Labrador, he releases nearly every wild salmon he catches and declines to serve them at Raymond’s.

Fishing, Mr Charles says, has made him “clear-headed” about food-sourcing decisions, but for some guys, it can be an exercise in acquiring more toys. “Writing a cheque for a bunch of gear is easy,” says Mr George Revel, a 31-year-old former fly-casting champion. “It’s harder to go out and catch a bunch of fish.” As the owner of Lost Coast Outfitters in San Francisco, Mr Revel needs to sell some gear to stay in business. But he also takes people fishing, whether he’s working with Project Healing Waters, a non-profit that organises outings to help combat veterans cope with PTSD, or helping high-powered tech execs relax with a rod in hand.

“A river is always different, always changing. You’re never playing the same golf course twice, if you will. There’s the water temperature, the bugs and when they hatch and how the fish react to that,” says Mr Revel, whose destination-fishing trips often fill up more than a year in advance. (An easier way to learn from him is to seek out the free after-work casting classes Mr Revel hosts in the summer in Golden Gate Park.) “Taking this information and assembling it into a story that makes sense is something that satisfies a lot of different brain types. There’s a lot of science involved in fly-fishing, but there’s also a lot of art.”

The US has a fine tradition of artists who fish. Think of all the writers moving out west to fish and write, among them Mr Anthony Doerr, winner of the 2015 Pulitzer Prize for Fiction, and of course the late Mr Jim Harrison, who often wrote about his beloved brown trout outside Livingston, Montana. In England, Mr Eric Clapton has been an avid angler since the early 1980s, when a summer’s worth of trout fishing helped him to recover from alcoholism and drug addiction. “Fishing is an absorbing pastime and has a Zen quality to it,” he wrote in his autobiography. “It’s an ideal pursuit for anyone who wants to think a lot and get things in perspective.” Lately the guitar legend has been fishing in Iceland, catching some of the biggest salmon in the world. One imagines that, after those trips, he wasn’t playing the blues.

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