For once the heads have got it together. A documentary that began life as an offhand gag from America’s “second-best pot comic” (as rated by the toker’s bible High Times) has made a tiny bit of cinema history. Super High Me follows the stand-up comedian Doug Benson as he abstains from marijuana for 30 days, examined by health professionals all the while. Then, armed with a prescription for “medical marijuana” – legal in his home state of California – he lets his freak flag fly and wakes and bakes for another month.

“It was just something I said on stage, a pun and a funny notion,” explains the unsurprisingly affable Benson. He followed a joke about how Morgan Spurlock’s acclaimed documentary Super Size Me had made him hungry rather than fearful with a suggestion that he could apply the same 30-day health regimen to pot. “I ran into a film-maker I knew, Michael Blieden, and he thought it could become a movie,” Benson says. “It took a few months, but it was still a surprise to me when we started making it.”

Spurlock’s 30-day trope is now so commonplace that one British wine writer recently spent a month drinking nothing but humble branded plonk. More seriously, Spurlock’s TV series 30 Days has him work at Wal-Mart and even serve a prison sentence.

Benson, co-author of the book The Marijuanalogues (are you sensing a theme here?), plays Super High Me for laughs – and all his antics are actually legal in California. “It would be difficult for anyone who has obligations to do,” he says. “So I wouldn’t break the law. I didn’t operate a motor vehicle for the 30 days of filming. The crew drove me everywhere. It’s a showbusiness thing. Someone outside showbusiness should try it and see how it works for them. But not a brain surgeon. There may be car mechanics that are already doing it, though.”

During his month off the sweet leaf, Benson appears sharper and harder, like a cucumber. Back on the bong he’s more like a marrow. Meanwhile, the federal authorities and California’s own lawmakers are at odds over the sudden mushrooming of dispensaries where those with a relevant doctor’s certificate can obtain medical marijuana (that nebulous complaint “back pain” serves for many). The sight of Drug Enforcement Administration agents shutting down legally registered, openly declared Hollywood premises seems absurd, though, not least when local stoners turn up to feebly wail “DEA, go away”.

The film holds the record for the widest documentary opening ever. It was shown in more than 1,000 venues on the holiest day of the smoking year, April 20, 4/20 in American parlance. Supposedly named for the after-school meeting time of a gang of Californian teen-agers in the Seventies, 4:20 is now a universal smokers’ code. Knowing that the film could not get television advertising or a wide release, the producers approached the indie marketing and distribution specialists b-side, which simply made screening copies available to anyone who wanted one and could offer premises.

“We thought: ‘Let’s not even try to make money’,” says Chris Hyams of b-side. “The real question was ‘Can you get stoners off the couch?’.

“Any dark room with places to sit can become a movie theatre, but we were stunned by the array of ideas and venues people came up with.”

From college campuses to comedy clubs, sympathisers joined in. An Illinois couple showed the film at their wedding reception. A San Fran-cisco “guerilla drive-in” outfit projected it on the wall of a local store.

“There’s hundreds of MBAs sitting round studios wondering how they can, quote, ‘make something go viral’,” says Hyams, the scion of a film family (his father is director Peter, his brother John an acclaimed documentary maker). The marketing budget for Super High Me was supposedly the same as the cost of a 2in advertisement in The New York Times. Judd Apatow’s forthcoming “weed action movie” Pineapple Express will not come so cheap.

Super High Me is amusing rather than deep. Some of the marijuana advocates featured are seriously intense, though, among them the Canadian “Prince of Pot”, Marc Emery. It makes for a strange scene – Benson cheerfully dopey, Emery, wanted by the American authorities for distributing cannabis seeds, understandably nervous.

Benson was unimpressed. “He’s a smart guy but he’s making himself a martyr. It’s like he wants to go to jail. I can get and smoke marijuana without going to jail. It’s not worth going to jail for.” He shrugs. “Maybe he smoked too much pot.”

Benson is aware that some on prescriptions for medical marijuana are scamming the system. “I don’t think they turn anyone away. But if it improves some people’s quality of life and it’s done privately, in their own home, why shouldn’t they have access to it?”

He himself took up the weed at the advanced age of 27. “As an adult I should be over it, but I still like it,” he says. Recently he appeared in a TV sitcom playing a Customs officer with the munchies, perusing passports while eating cereal straight from the box. “I may be getting type-cast,” he worries.

Physically, though, he’s sound enough. “The doctor gave me a clean bill of health,” he says of his experiment. “So eating burgers is worse for you than smoking pot.”

Super High Me will be released in Britain later this year

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