"I'm not real!" shouts the lead character in Duncan Macmillan's full-throttled, raw and real study of addiction that has transferred to the West End after a sold-out run at the National Theatre. And it's true of course, she's not real: she's a character called Emma played by actress Denise Gough in People, Places and Things. But it's also true because Emma, an actress too, is genuinely unsure about where reality begins and ends.

It's a little confusing, yes, but all this meta-theatre is less about messing with our heads and more about demonstrating just how chaotic Emma's is. The audience sees what happens onstage partly through Emma's eyes but it's entirely unreliable because Emma lies a lot. So much so that we're never sure what her name actually is. Lying is one of the things you're absolutely not supposed to do when you're getting clean, which is what Emma is trying to do. Turning up at a rehab clinic high as the highest kite there is, she has pumped herself with a very long list of drugs and booze for a long time and admits, in slurred tones in a heap on the floor of the doctor's office, that if she uses again, she might die.

Watching someone get through the first 28 days of sobriety doesn't sound like the most fun subject for a play, and at times it's an extremely difficult journey to witness. Emma is on self-destruct mode and she absolutely hates the 12 step programme – a way of getting off drugs originally orientated around finding God, now modified to be ‘religiously neutral'. "Give yourself up to a higher power," is the mantra but she refuses to surrender: she's a bright, difficult, independent atheist. But if she doesn't let go, she isn't going to get better. It's as simple as that.

Emma is an absolute firecracker of a role and Gough portrays her magnificently. Right from the early scenes where she has a meltdown while acting onstage in The Seagull – she's an eye-swivelling, gurning, staggering mess desperately trying to get her lines out – she shows us how drinks and drugs envelop a person. Gough is onstage the entire time, depicting a barrel of self-loathing and defiance all mixed up with speed, vodka and pills. It's a tortuous physical and emotional journey that Gough plays with astounding commitment.

People, Places and Things certainly isn't gratuitous, righteous doom and gloom. Gough is dryly witty as Emma, a woman who readily calls her mother a c**t and thinks it's "the world that's fucked," rather than her. Gough knows when to focus on the laughs and when to ramp up the weeping. It's a sharply observed story that has a strong ring of truth to it. From the awful group therapy sessions that Emma repeatedly resists contributing to, to a shocking confrontation with her parents, there are no rose-tinted glasses through which to watch this. It features all the highs and lows of life while deftly highlighting just how limited treatment for addiction is today.

Jeremy Herrin's production has some excellent quirks. The staging at Wyndham's is the same as it was at the National – there are seats on both sides of Bunny Christie's white panelled set which results in a great early moment of reveal. Herrin also plays with Emma's hallucinations – the world actually melts around her. Time jumps, there are blackouts and booming sound rips through our ear drums as if from nowhere.

Ultimately, Macmillan's play is all about the role at its centre which is performed seamlessly by Gough. But it's a strong work on its own with writing that stands up and whacks you round the head as it grapples with what it means to be human in a world that seems so entirely broke. Writing like this in the hands of Gough is a heady, superb and intoxicating combination.

People, Places and Things runs at Wyndham's Theatre until 18 June.