'One of the bigger crisis moments of my life." That's how Mike Mills describes making his first feature, Thumbsucker, which won the Guardian first-time directors' award at this year's Edinburgh film festival. He says it with such calm now. But six years ago, doors were being slammed in his face.
"Every distributor and producer in North America, Britain, Europe said no to me," he recalls. "People kept saying: 'It's unmarketable, it's unmarketable, it's unmarketable' ..."
Mills has made ads (Nike, Levis, Volkswagen) pop promos (Air, the Divine Comedy), short films and documentaries. He wasn't used to hearing no. "I've never had that much rejection in my life. I didn't know where I was. I just kept going 'cos it took me so long to write the script."
What made it harder was that a very attractive cast of actors was interested in the script."People like Tilda Swinton, one of my heroes, and Vincent D'Onofrio wanted to be in the film. But still no one wanted to make it."
The script that Mills had such faith in is based on a book by Walter Kirn. At its heart is Justin, a 17-year-old who still sucks his thumb - a signal of insecurity that horrifies Justin's father but fascinates the "holistic orthodontist" who gives him hypnotherapy. The deep-seated fear Justin has, which keeps his thumb in his mouth, is that he and his father are not good enough for his mother, and she might leave. As Justin navigates the problems of late adolescence, his parents peel back the layers of their issues, too. What it means to be "normal", and accepting your "weird self" are the themes.
The script balances Justin's growing pains with a lot of humour - and uncovers the love that lies beneath a family heading for an emotional pile-up. The fact that there are parallel stories, that the journeys of both Justin and his parents are key, seems to be what scared the marketing people. That and the un-Hollywood portrayal of love.
"I had to spend a lot of time in America saying: 'This is not a dysfunctional family. What is dysfunction? Are you functional?' In the UK they understand it's like two coming-of-age films. In American it's just lumped into this quirky independent box."
The greater the resistance Mills encountered as he tried to get the film made, the more he dug in his heels. "The marketing thing pissed me off. It shows deep disregard for the audience, for life."
He had other reasons to cling to his dream: in 1999, early in the film's development, his mother died of cancer. "You come out of that fresh to life: this is my limited opportunity. I have to go as far as I can. Then soon after I started working on the film it was like: 'Woah! I am Justin, and Audrey [Justin's mother] is my mum. Me trying to be her perfect peer, persuading her not to leave. It became a part of my mourning process."
Filming finally began after Vince Vaughn and Keanu Reeves (who plays the orthodontist) came on board. The finished result is remarkably restrained for a director with a background in pop and advertising. Mills says he even had to get the sound people to strip many of the "atmos" effects, insisting on a quiet realism. The idea of trickery bothers him, right down to the acting.
"Actors are pretending for you," he says, "but they're not lying. They are not putting on a guise instead of themselves. They are finding things inside that they have experienced."
As Thumbsucker was being edited, Mills' father died. "So there was this weird mirroring. On one level the film is about individuation from your parents, you know, and Justin is waving goodbye at the airport - and my dad had just gone. Agggggh! Crazy ..."
I have to pop out of the room where we are talking. When I return, he is filming the bubbles in my drink with a tiny digital camera. It reminds me of the way the camera slides off people and on to everyday objects during shots in Thumbsucker.
"That drifting thing is my life view. I do it a lot. I am intrigued by inanimate objects. They're a piece of history, someone's statement and ideas of life. If this was your room, the stuff on your table would be telling me as much about you as you. As someone who grew up in a house where there wasn't a lot of talking, I'm used to just looking at the world. And in general I often feel like I just don't understand what's happening. That everybody else does, but I don't quite get it. That camera technique I often call 'the alien that landed - and doesn't know what's important'."
Mills says that uncertainty and "a broken-ness" are the heart of Thumbsucker and of a lot of his work. The film clearly reflects things he has felt growing up. He looked for these same feelings in his actors during rehearsals - a willingness to push themselves to vulnerable places. He saw more than 100 hopefuls for the part of Justin before finding Lou Pucci, who ended up winning the Special Jury prize for acting and the Silver Bear for best actor at the 2005 Sundance film festival.
Pucci, he discovered, had never had formal acting training. "I was like, 'You're young; how do you act?' He said he has a sentence in his head that he keeps saying all the time, and if he falters he just falls back on the sentence. I said, 'Wow, what's the sentence?' And he said, it's 'I don't know.'"
Those unknown, unmarketable things are what make Thumbsucker rich, the confusing places in between packaged certainties. "It's the can't live with, can't live without thing," says Mills. "The huge vulnerable-making machine that love is"
· Thumbsucker is released on Friday.