ALISON ROWAT

WHEN it comes to having a mid-life crisis one has to laugh. That was certainly the attitude when While We're Young opened the Glasgow Film Festival in February. As the forty-something lead, played by Ben Stiller, disgraced himself with such acts as wearing a pork pie hat and taking up cycling, a tide of mirth and buttock-clenching self-recognition worked its way through the Glasgow Film Theatre like a Mexican wave.

Even hipsters, it seems, get the middle age blues.

As for any age-inappropriate behaviour the film's 45-year-old director Noah Baumbach might have indulged in personally, he largely prefers to take the Fifth Amendment.

"I've yet to wear a hat," is all he will cough to.

So there is nothing in the film he will admit to doing?

"I wouldn't admit to it, but I would say that most of them are representations of other foolish things I have done," he laughs.

Asking about a link is pertinent because Baumbach, from his first picture, Kicking and Screaming, through to The Squid and the Whale, Margot at the Wedding, and Greenberg, is often held to be one of the most autobiographical writer-directors of his generation. The truth, or otherwise, of that is revealed as we talk through his career. But first, While We're Young.

Stiller stars as Josh, a once hot filmmaker whose career and marriage to Cornelia (Naomi Watts) have settled into a cosy, bordering on comatose, state. When the pair meet up-and-coming documentary maker Jamie and his wife Darby (Adam Driver and Amanda Seyfried) they start to act like twenty-somethings again. Cue the hat and, for Watts, a segue into hip hop and krumping (failure to know about the latter is a sure sign this film is for you).

For Baumbach, While We're Young is less about mid-life blues than how couples stay together. When it came to casting the piece, Stiller, with whom he worked on Greenberg, was the film's foundation stone. Then came the Jamie character, the one who turns Josh's head.

"The casting of Adam Driver was extremely important. It helped the movie make sense. It's tricky because I've always felt like on one hand we're having fun at Ben's character's expense, watching him kind of fall for this younger couple. I knew the audience was going to find it amusing to some degree and it was intended as such, but I also didn't want to sell the character out, make it too foolish." Jamie, a mixture of charm, energy and ruthless ambition, had to be a plausible Pied Piper. "You kind of want to follow him anywhere."

While We're Young is Baumbach's first film since the 2012 comedy Frances Ha, co-written with his partner Greta Gerwig. Baumbach was previously married to the actor Jennifer Jason Leigh, with whom he has a son.

The tale of a young sofa-surfing Brooklynite (Gerwig) trying to find her place in life, Frances Ha was a more joyous piece than the more sombre Greenberg and Margot at the Wedding. It seemed like the work of a filmmaker falling in love with the form all over again. Would he agree?

"It's certainly fair if that's how it feels. When I'm making these things I'm not in the narrative of how they are going to be seen, I'm just trying to make something that's the best thing I can do at the time and the thing that feels like the livest wire for me. I loved making that movie. It was very pleasurable. If people feel like it energised me that's fine too."

Frances Ha must have been something of a relief for Baumbach in as much as the lead was a woman, meaning he could avoid the usual questions about how much of his own life he had mined. Such questions have followed him since The Squid and the Whale, which recounts the divorce of two writers and the effect on their children. Baumbach's parents, also writers, divorced when he was young.

He admits that early in his career he would get tired of such questions, but these days he is more relaxed. "At this point I'm used to it and I probably court it to some degree," he laughs. "I wouldn't make any of these things if they were actually revealing in a way I wasn't comfortable with. For me they are all fictions and reinventions." There are "surface autobiographical elements" in The Squid and the Whale he says, but it is "entirely made up".

"There is so much of that movie people assume is true and isn't. Other movies have things that are probably equally autobiographical in some ways, but not as maybe clear-cut. I make personal movies, that's the kind of filmmaker I am and I write the things I make so they all come from me. It's a relationship with the audience I accept and at this point can maybe play with a little bit."

For While We're Young he was back to writing alone. His principal writing partner in the past has been Wes Anderson, with whom he wrote the screenplays for Fantastic Mr Fox and The Life Aquatic with Steve Zissou.

The problem with writing scripts alone is that you don't get any credit for what has gone before, he says. "I always feel it would be nice if you could use the last 50 pages of the previous script. Really you feel like a total amateur all over again. When you collaborate you have a friend, and it starts as a conversation. It's an easier way to get into something."

Notwithstanding his pleas about there being little connection between screen life and real life, I'm still intrigued as to how middle age is treating Baumbach personally. He mentions a scene in the movie where Stiller's character visits the doctor. When Baumbach was younger he would complain to his doctor about something only for the medic to shrug it off as overreacting.

"I felt safe doing it because I knew he was going to. I remember that shift when I would mention some kind of pain and the doctor actually started taking me seriously, like saying maybe we should get you an MRI. That part I don't like about middle age."

While there was a three year gap between Greenberg and While We're Young, Baumbach is losing no time in releasing his next picture. Mistress America, another coming of age comedy starring Gerwig, premiered at Sundance in January and should be out later this year. It is a very different film from Frances Ha, he promises. "It felt different to us, I don't know what other people will say."

The film secured distribution even before Sundance, another signal, together with the toasty critical reception in the US for While We're Young, that Baumbach's career, unlike that of the fictional Josh, is in spectacularly rude health.

"On the whole there are more positives than negatives," Baumbach agrees when asked to sum up getting older. "There's a relaxation that comes with age. I felt I was older at 28 than I feel now."

(itals) While We're Young opens in cinemas tomorrow