The two stars of Sophie Hyde's Animals – adapted for the screen by the author, Emma Jane Unsworth, from her own novel – are slipping out of the hotel room where our interview is due to take place. With a cheerful nod Alia Shawkat and Holliday Grainger walk past looking as thick as thieves. It's tempting to imagine that they are emulating the unruly characters, Laura and Tyler, who inhabit the film.

Animals charts the course of a friendship between two creative women that's almost at breaking point. One is on the precipice of turning 30, the other already navigating this transitional period of questioning every life decision she's ever made while also being firmly stuck in a debauched whirlwind of booze, sex and drugs.

When they eventually return to the room, I ask them how much they were drawing from real life for their roles. Grainger begins by saying, 'I think that was the basis of most of the rehearsals, that me, Ali and Sophie were talking about our own experiences, friendships and relationships and how we relate to Laura and Tyler in specific ways …' She laughs then adds, 'I'm not gonna go into those with you though!" Shawkat chips in saying, 'We're both 30 so we were at very similar stages as these characters' so it was easy to pull from.'

There have been comparisons to Withnail and I in the women's dynamic, a film that Hyde took inspiration from, with Shawkat taking on the role of instigator, Tyler, who becomes resentful of Laura's decision to pull away from their partying to focus on her writing and make a go of it with a man. 'Even though the book wasn't written that long ago, the characters and especially Tyler live in the past,' explains Shawkat.

You can feel the fondness and nostalgia for the intimacy and pleasure of female friendships formed in your 20s throughout Animals, where the good times begin to whizz past in an instant and the hangovers eventually linger more prominently. 'Tyler wants to live in an era where debauchery was more fashionable,' says Shawkat. 'I was talking to someone the other day about cocaine, like in the 1970s how many of our favourite films were made with people totally on cocaine the whole time? A friend of mine, a writer, was like maybe we should just try it! I was like, I don't know! I don't know if I could focus. Now I have a glass of wine, and the next day I'm bloated! I think also it is a state of mind, but I think the film in a way shows that beautiful arc at the beginning – it seems really fun and then by the end you want to take a shower and have a green juice!'

As our chat winds down Shawkat reflects on the current state of things, with the conversation turning to Beyoncé's Homecoming documentary, 'I was sick in bed a couple of weeks ago and watched it and I was being hard on myself, like I gotta be healthier and I've got to take care of myself. I was watching it and was like, my god! This woman! She really inspired me. Beyoncé's human and I was like if she can do it, goddammit I can get out of bed and make myself a smoothie! Lately I've been trying to take care of myself so I have energy to see people and go to work.

'I feel lucky that we get to be artists for a living so our job is to be commenting on the state that our world is in right now.' She continues. 'It produces amazing art because we're talking about all the scary things that are happening. Some of the best art comes from post-war dynamics. Thank god we're not in a world war but it's like a different version of it is happening. An internal war is happening. I don't mean to say, great, the world's fucked up so we can make good art! But it's like our art actually has more weight and urgency to it. It actually makes more of a difference.'

General release from Fri 2 Aug.