Those screaming, crying teenage girls losing it over One Direction may seem like a mindless mob duped by clever record companies. But a new documentary tells a deeper story.

I Used to be Normal: A Boyband Fangirl Story is about the (mostly) teenage girls who devote themselves to boys in groups of four to six who sing songs designed to hit them right at the nexus of their hearts, minds and hormones. But the film is also about the effect music has on humans, and the identity-forming experiences of adolescence. It's for anyone who's felt a pang of nostalgia hearing a song they loved as a teen.

Melbourne director Jessica Leski fell hard for boy band One Direction later than your average fan – it was 2012 and she was 31. "It made me look at other boy bands," she says. "I saw how formulaic it was. And it made me analyse why that formula is so powerful." But what she found even more interesting was the way fangirls are so often dismissed as "simple" or "just going through a phase".

"We always see teenage boys get excited about sport – and not just teenage boys, grown men can have posters on their wall, re-watch their favourite grand final, create their 'dream team' and our society celebrates that or respects that. But when a girl gets excited and passionate about something it’s dismissed, and I think that’s really unfair," says Leski.

Leski has met fangirls in the US and Australia that own their passion and use it to create material of their own. "It was the first time I’d seen fan art and fan fiction, and it was a much bigger world that I realised," says Leski. Fangirls can form accepting and inclusive online communities. And these online spaces are safe and encouraging for young girls at a time when they can be vulnerable.

Adolescence is when girls experience a drop in self-esteem and depression rates go up. Fangirls are empowered by their fandom, make deep connections with each other and have an outlet for personal expression. Educators and psychologists Leski interviewed believe that validating fandom, rather than dismissing it as trivial and temporary, is important. It can set girls up with the self-esteem, passion and skills they will find useful as adults.

Leski spoke to fans from all over the world of all ages – of The Beatles, Take That, Backstreet Boys, N*SYNC and more – to find out what role being a fan played in their teenage years, and into adulthood. She found that what you fall in love with as a teenager forms part of an individual's identity as an adult.

"We spoke to neuroscientists about what music does to the brain, and to find out what’s going on in the teenage brain," says Leski. "During adolescence the brain is going through a huge rebuilding and restructuring – they’re feeling a lot of things for the first time. So going to a concert is overwhelming. Finding a song that you like, seeing a boy you think is cute, form all these connections in your brain that didn’t exist before," she says. Leski and the film's producer, Rita Walsh, have hundreds of hours of footage – interviews with boy band alumni, adult fans, parenting experts, music therapists, record-company execs and pop-culture critics. They have shot 85 per cent of what they need to finish I Used to be Normal.

There is a Kickstarter campaign running that, if successful, will allow Leski and Walsh to release the film in 2017. "Although the film is about boy bands, it’s really about how you form your identity as a teenager," says Leski. "I want to show that it’s a really positive thing. The media’s favourite picture is just of women screaming. But there are beautiful communities, there’s art being created. And I don’t think people think about that," she says.

See the trailer for I Used to be Normal, support the Kickstarter campaign and find out more about the film here.