Nadine Garner: 'You don't want to get on bended knee to your child and go, please treat me with a bit more respect'

Her interest in performing work about mental health began a year ago, when she performed in Tell Me I'm Here at Belvoir St Theatre in Sydney, which is based on the acclaimed writer and journalist Anne Deveson's heartbreaking family memoir about her son Jonathan's experience with schizophrenia before he tragically ended his own life. Garner played the role of Deveson.

"Performing it was probably the hardest job I've ever done," says Garner. "And I became really aware of the role of theatre in terms of community outreach.

"We had so many carers come to the show and I would spend hours talking with them, mostly women who'd spent their lives … singlehandedly trying to manage children who no one really wanted to know about."

The experience gave her a deep appreciation of the impact theatre can have on an audience which rarely sees itself reflected on the stage. "Something fundamentally shifted in me in regards to what theatre can do," Garner says. "And it's not just about entertainment, it's actually about community service."

It is a theme she has returned to in the new play The Almighty Sometimes. The Melbourne Theatre Company production is playwright Kendall Feaver's award-winning debut about 18-year-old Anna (Max McKenna) who has lived with serious mental illness since childhood and her well meaning but stifling mother Renee, played by Garner (Louisa Mignone plays Anna's psychiatrist and Karl Richmond plays her boyfriend).

When Anna decides to stop taking her medication - because she believes they are inhibiting her creativity - Renee is frightened her daughter will descend into illness again. It's not really a spoiler to tell you that yes, she does.

But this is not a story about pharmaceuticals, but rather the tension between a child's independence and a mother's care. The play explores this close, often claustrophobic relationship, as well as society's relationship to mental illness, through Anna's coming-of-age story.

"It's a difficult time to navigate being a human being and to understand what an authentic life experience is," says Garner. "What this play does is open that box up. It doesn't give an answer, but it opens the box up to say, let's all just stay open-minded and open-hearted about what it is to be living a life."

I ask: how has the well-heeled MTC audience responded to the show's moments of darkness and distress (as well as humour and joy), including a scene where Renee has to physically wrestle Anna to the ground and remove pills from her mouth?

"I said to the MTC that we need to keep first and foremost in our mind the impact the show will have on people," Garner says. "This is stuff that is going to have big echoes, and every single person in that audience has either lived experience or secondhand experience [of mental illness]."

Within the emotional crucible of acting, Garner has had to find ways to sustain herself. She has practised yoga for 30 years, does qigong, is a shiatsu therapist and works as a "wellness coach" for the cast of Neighbours.

We stop walking and sit on a couple of plastic chairs next to rows of bright sunflowers and pink zinnias at Joe's Garden, a two-acre farm right next to the creek. Tiny children zip past on scooters, people walk their dogs and the glossy sunlight burnishes the creek. We commiserate about the climate crisis and ponder what the next 100 years might hold. (Garner hopes for a retreat into smaller communities and a simpler way of life.) We talk about teens and their phones and social media and how it feels like corporations are calling the shots while parents and society are facing the consequences.

Garner was adamant about keeping phones away from their children when she was younger, but it's different now they're teenagers. It's a discomfort shared by many parents. "I feel like the genie's out of the bottle and I personally can't stuff that genie back inside," Garner says.

"Not so long ago people grew up with magazine stands [with someone] sporting a nice miniskirt and you might go, oh, I wouldn't mind that miniskirt, and that was about it.

"But there was no … (she pauses) … inundation of perfectly shaped buttocks and perfectly shaped lips and all these things that young women and the men are now supposed to have in order to be acceptable."

To inhabit the character of Renee, Garner drew on inspiration from her own life as a parent. She strongly identified with Renee's desire to be seen by her child - and society more widely - as a whole person, not just a provider.

"You get to a point when you've been raising children for 18 years, where you just go, oh, I actually feel like I now need to reclaim something of myself back.

"You don't want to go on bended knee to your child and go, can you please treat me with a bit more respect? But Renee ends up doing that at the end of the play … I think that's a really brave thing, because I think it's hard for mothers - I don't think anyone condones that."

One of the most poignant moments in the show comes when Renee tells her daughter that she, too, is clinically depressed. "I exist," she says in a whisper, a carer's appeal for recognition.

Garner feels huge compassion for the carers of people with serious mental health conditions, such as Deveson.

"I can't fix it," she says, with a small shake of her head. "And I can't get people on to the NDIS who definitely deserve to be there. But I can tell a story that makes people feel seen."

• The Almighty Sometimes is on at the Sumner theatre in Melbourne until 18 May.