When Keven McAlester began making a documentary about the life of rock icon Roky Erickson in July 1999, he thought he would be telling a familiar story about yet another Syd Barrett-like casualty of the 1960s. Erickson, the lead singer and guitarist of the psychedelic group the Thirteenth Floor Elevators and a major influence on everyone from R.E.M. to Primal Scream, had been arrested in 1969 in Austin, Texas, for possession of a matchbox of marijuana.

Rather than face a prison term, he pleaded insanity, and spent the next three and a half years in the Rusk State Hospital for the Criminally Insane, where he underwent electric shock therapy and treatment with psychoactive drugs such as Thorazine. By the time he came out in 1973, he was a different man. For the next two decades he battled schizophrenia, occasionally making increasingly dark records, before losing interest in music and becoming a recluse living in poverty.

When we first see Erickson at the start of You’re Gonna Miss Me, McAlester’s documentary, which is being screened at the London Film Festival, the 53-year-old is sitting in a cluttered apartment in Austin with four radios, three televisions, two amplifiers, a radio scanner and an electric keyboard playing to drown out the voices in his head. He has three teeth and his hair is matted into one huge dreadlock. Watching him shuffle around the apartment muttering incoherently to himself, the refrain of “You’re Gonna Miss Me”, the Elevators’ 1966 hit, “I’m not coming home” seems horribly prophetic.

“I was interested in how this incredibly talented person ended up in this dire situation we see him in,” McAlester says. After a year of filming, however, the documentary started to develop a momentum of its own. Partly as a result of McAlester spending time with Erickson’s mother and his four brothers, a battle between them developed over how Roky, unable to speak for himself, should be cared for.

McAlester ultimately came to see this family drama unfolding in front of him as more interesting than what he calls the “fascinating but ultimately static” story of Erickson’s tragic decline into schizophrenia. In the end, he spent a total of three years shooting, and what resulted was a completely different and much more ambiguous film than the one he had planned to make back in 1999. “The film I imagined was what turned out to be the first 25 minutes of the film,” he says. The story ended, completely unexpectedly, with Roky returning to his music after nearly two decades.

Roger Kynard Erickson grew up in Austin, where he absorbed the influence of rhythm and blues and in particular Little Richard and James Brown. It was the combination of Erickson’s yelping tenor voice and Tommy Hall’s fluttering “electric jug” that created the distinctive Elevators sound, described in the documentary by Z.Z. Top’s Billy Gibbons as having an “enjoyably frightening intensity”. It inspired, among others, Janis Joplin, who nearly joined the group before moving to San Francisco.

In 1966 the Elevators released their first album, The Psychedelic Sounds of the Thirteenth Floor Elevators, which included “You’re Gonna Miss Me” – the song that Erickson had written and already recorded with another group, The Spades, and which would be the Elevators’ only ever U.S. chart hit. After they performed it on American Bandstand, the show’s host Dick Clark asked Hall who was the head of the group. “We’re all heads,” Hall replied.

It was Hall who had introduced Erickson to acid, which became an increasingly big part of his life and his creative process – but also made him a target for the Texas police (“I was more of a country and western guy myself,” says the then Austin police chief in the documentary). In 1966 the Elevators had been to San Francisco, where their hard, R’n’B-influenced sound transformed the folk-based West Coast scene, but instead of staying in California as many urged them to, they returned to Texas, where Erickson was arrested. By that time, however, his life was already unraveling as a result of his drug use; he was already hearing voices and he was diagnosed as schizophrenic.

In the 1970s, after his release from Rusk, Erickson made a series of musically brilliant but lyrically bizarre records such as “Two Headed Dog” that he described as “horror rock”. He became obsessed with aliens and believed a bugging device had been installed in his teeth. As a result of a series of exploitative contracts, he was receiving almost no royalties for his music and ended up living in a housing project in Austin, where he was arrested for stealing other tenants’ mail and taping it unopened on his wall.

McAlester, a music journalist who had grown up listening to Erickson in his native Texas, began to think about making a documentary on the musician in 1998. At the time Erickson’s only contact with the outside world was through his obviously depressed and controlling mother Evelyn, who had refused to allow other family members, including Erickson’s own son, to see him. Perhaps partly as a result of Erickson’s experiences at Rusk, she was also deeply suspicious of psychiatric treatment, and so Erickson was receiving no medication for his schizophrenia.

The catalyst for the struggle that was to ensue was Erickson’s youngest brother Sumner, a tuba player with the Pittsburgh Symphony Orchestra. McAlester was interested in him because he was the only one of the five brothers who had escaped the family, though he too had been through years of therapy. Sumner, 15 years younger than Roky, had been taken to visit him at Rusk when he was a child but had had little contact with him for a decade. After talking to McAlester, however, he decided he needed to intervene to, as he puts it, give Roky his life back. “I just didn’t want the movie to have a sad ending,” Sumner, now living in Austin again, says. “I was ready to give him some options.”

Eventually Sumner would have to take legal action against his mother to gain access to Roky; in June 2001 he was granted legal guardianship and took him to Pittsburgh to live with him. Four years later, Erickson, now 58, is living in his own apartment in Austin, back on medication and even has his driver’s license again. When I call him at home, he is attentive and is able to have a coherent, albeit basic, conversation. “Things are going really well,” he tells me cheerfully.

But perhaps the most positive sign of recovery is that Erickson has started to play again. The climax of the documentary comes when Erickson picks up a guitar and suddenly seems at peace with himself. In March, he played three songs at a fundraising concert in Austin – his first gig since 1987. “It felt good,” he says. Last month, he played in front of 65,000 people at the Austin City Lights festival – his biggest ever gig.

The Roky Erickson Trust, run by Sumner, recently reached a settlement with Charly Records, the British record label that now owns the rights to the Thirteenth Floor Elevators’ back catalogue, and Erickson is finally being paid for all of his releases. A Hollywood movie about Erickson’s life is also in the pipeline, which the family hopes might lead ultimately to his induction into the Rock n Roll Hall of Fame in Cleveland, Ohio. Roky Erickson might not have come home yet – perhaps he never will – but he seems to have found a happy place to stop along the way.

A version of this article originally appeared in The Times, October 20, 2005.