Kate Dickie: 'I've been angst-ridden all my life'

Kate Dickie comes bounding in, cheeks glowing and nose tip pink, shaking the first snow of Glasgow's winter from her shoulders and apologising for her lateness. "I had to run here on this slidey snow," she says. "I was on my arse most of the way." A peal of raucous laughter echoes around the cafe she's showering with a flurry of melting flakes.

It might be a surprise that Dickie turns out to be an unguarded and animated conversationalist, and rather intoxicating company. But since her performance as Jackie, the still, stony CCTV operator mourning the death of her daughter in Red Road (the Andrea Arnold film for which Dickie won a Scottish Bafta in 2006), she has carved out a series of serious roles, bringing life to damaged, repressed and ostensibly unsympathetic women who hide in the shadowy corners of bad places.

Having bolstered her reputation with white-knuckle portrayals of a heroin addict in Caroline Paterson and Stuart Davids's harrowing Wasted, and a grieving mother in Morag McKinnon's Donkeys, she now stars opposite James Nesbitt in Colm McCarthy's British horror Outcast, as a guilt-ridden, pain-filled woman trying to save her teenage son from a curse, in the form of the super-naturally empowered shape-shifting Irish Shi.

Dickie confesses she has a general distaste for horror films (as well as being a squeamish "scaredy-cat" who insists her boyfriend accompany her to the bathroom if she hears a creak in the hall), but these considerations were outweighed by the appeal of playing a woman driven by such a complex sense of purpose.

"I really felt for her, she's been alone her whole life with no contact, no affection, or love, always having to keep people at arm's length," she says. "She comes across as very tough and brutal with her son, but it's all because she would do anything to protect him, which as a mum I totally understand. That's what makes you strong.

"I do wonder if people watching will think Mary is just a hard-faced cow. God, I just hope it's obvious why she's like that, how her past has affected her, why she can't allow herself to have a relationship."

It's typical of Dickie to see the redeemable in an ostensibly hostile and forbidding character. Ask about her motivation for wanting to act, and she replies that for her it's a somewhat unfashionable question of social responsibility.

"I don't feel drawn to lightness, I need something more," she says. "I feel that – oh, I hate saying this, it sounds so wanky – but I feel a real urge to give voices to people we don't usually hear from in real life. There are always reasons for people's behaviour, and it's easy just to dismiss them and assume that we already know their story, especially if they're no good at showing their emotions. Life gives you all these knocks, it's so easy to form a shell to protect yourself. I've done it myself."

This is not a casual assertion. A nomadic childhood, which began in the Lanarkshire new town of East Kilbride and took in Perthshire and the small Dumfriesshire town of Newton Stewart, meant Dickie had to face being the new girl more than once, and though she credits the experience with giving her a "big mouth and a thick skin", she says she cried every night for six months when she changed schools at 13. Her adolescence was spent "worrying a lot" – about "where to put myself in the world" and then about the rapid decline of her mother, ravaged by Alzheimer's in her 40s. She died when Dickie was just 23.

"It was hell on earth," she says. "I can't put it any other way. Poor mum. She was so young, such a beautiful, bright woman. It was just shit. Dad tried to put her in a private home, but they couldn't cope with her anxiety and she ended up in a locked ward in a psychiatric hospital. And that's where she died. It was the worst possible place for someone with Alzheimer's to be."

"I don't actually think I've ever … I don't talk about this much," she says. "I lost my dad a few years later, too. It does get easier eventually, you stop crying all the time, but I think a lot about all the things they're missing, like [her six-year-old daughter] Molly and my work. I miss sharing things with them. They were very supportive of my acting when I started drama classes. My dad told me to go for it."

Dickie began Saturday-morning acting classes when she was still at school and won a place at the Royal Scottish Academy of Music and Drama in Glasgow when she was 18. After a decade of theatre work, she slowly broke into television, getting small roles in Scottish TV dramas such as Tinsel Town, Still Game and Taggart, before catching Arnold's eye when casting for Red Road. The daughter of a farmer, Dickie says she was initially worried people would think acting was a lightweight way to make a living. Her father was very strict regarding the frivolity of vanity, forbidding his two daughters from looking into mirrors, and Dickie still finds the experience of being looked at difficult. "I hate going into a room with people in it and the feeling of them staring. I find every moment excruciating." Nevertheless, acting became a sanctuary for "someone looking for something to hide behind".

There are a number of stories pertaining to Dickie's bashfulness. She had a panic attack before the Cannes premiere of Red Road and had to be dragged there by Arnold. While making the same film, she dived red-faced beneath a duvet between every take while shooting a graphic sex scene. Though she insists acting is her ideal job because "I get to be someone else and then it's not about me", she still struggles with the demands of the red carpet and shudders at the mention of Botox.

"I feel really strongly about that. Even though my heart sinks when I look in the mirror and I think, 'Oh God, I really expected you to look younger,' I would never, ever do it. It makes me feel sad." She points to two furrows on her forehead. "I really hate them but they're part of me and I think all your bits and bobs are … they're your life, aren't they? I don't want to be fighting myself, I want to be at peace with myself and part of that is accepting that you're ageing. I'm nearly 40 now. I've been angst-ridden all my life, but finally I'm in a place where things don't matter so much."

In fact, the Red Road experience was a whirlwind for Dickie, who hadn't attracted much attention up to that point. Suddenly she was being blinded by paparazzi, and winning awards all over the world. She describes herself as coming out of that time "shell-shocked" and says that for a few months afterwards she sat at home, with the phone noticeably not ringing, wondering what would happen next.

She returned to theatre for a while, but gradually, the Red Road effect began to kick in. Shane Meadows snapped her up for Somers Town in 2008, and she played a small role in the TV adaptation of Ken Follet's medieval-set novel The Pillars of the Earth. Slowly but surely, she has found a place in the industry, for which she is emphatically grateful and possibly, to some degree, still in shock.

"You know, I really have to credit Andrea Arnold. She was the one who kept telling me: less acting. She taught me so much. I always feel embarrassed when people tell me I was great in Red Road or whatever – I feel I shouldn't take credit for it. Whenever I get a job I call my sister and say, 'Oh God, I'm going to be found out this time.'"

Her next project is A Game of Thrones, an HBO series based on the fantasy books by American author George RR Martin. She just has time to tell me that her character Lysa is a "troubled, lonely" woman, at which revelation she pulls a self-mocking face: "There's a surprise."

Outcast is released on 10 December.