Within three minutes of sitting down opposite Nadine Shah, the musician is trying to sell the house on the Kent coast she still shares with her ex-husband to me, or indeed anyone reading this. “No one wants it, so I’m going to try and make this article an advertisement for how Ramsgate is amazing,” she jokes.

Shah is a singular force in British rock, as funny and charismatic in person as she is on stage and in song. The Tyneside songwriter’s atmospheric, tragicomedic post-punk songs tackle tough themes with an acid tongue, and find absurdity in bleakness: her 2017 Mercury prize-nominated album Holiday Destination had songs about the Syrian refugee crisis and Islamophobia. The follow-up, Kitchen Sink, sent up the sexism she has experienced as a woman in her 30s, and depicted men selecting mistresses as if they were livestock.

After her debut album, 2013’s Love Your Dum and Mad, written after the deaths of two former boyfriends, Shah became an ambassador for the mental health charity Calm; she has called out issues such as the music industry’s gender pay gap, the unfairness of the streaming economy for musicians, or the “racist bullshit” she’s faced because of her Muslim surname (her father is of Pakistani heritage). Now, drinking tea in a London bar, she is self-effacing: “I think a lot of people found me righteous before, like: ‘If she’s not talking about how we should save refugees, now she wants to fix streaming. And here she goes again.’”

But Shah is extremely likable; unfiltered and a champion of what she believes in, including the ever-dwindling music press. While plenty of musicians are suspicious of critics, in lockdown she created an Instagram Live series called Payback, where she interviewed music journalists about their jobs. “We’re losing all our best writers because no one’s getting paid for it,” she says.

The house sale marks the end of a tumultuous period in her life. In 2018, Shah left London to go home to Whitburn, South Tyneside, when her mother Heather was diagnosed with stage 4 lung cancer. “I dropped everything,” she says.

Heather had been predicted to live a few years but the pandemic “sped things up even quicker”, says Shah. “Not being able to leave the house as she was high risk, her mental health started to deteriorate and in turn her physical health, too.” While looking after her mother, Shah started writing Kitchen Sink. “It was a really awful time,” she says. “I was caring for the person that I love the most in the world and watching her die, and I started abusing substances.”

Kitchen Sink came out in June 2020; her mother died two months later. With little work, having lost gigs to lockdowns, Shah’s substance use worsened. “I’m never going to go into the details of what I did, or what drugs I was dealing with,” she says. “It can be very glamourised.” Not long after, she moved to Ramsgate to live with her boyfriend, an old friend who had directed one of her early music videos. They got married in the summer of 2021, as her addiction and mental health issues were becoming even worse.

“Things were very erratic and I was going 110 miles per hour, trying to pretend everything was fine,” she says. “I was really unwell on the day of the wedding. I’m hardly in any of the photographs. And then it carried on.”

Eventually Shah started having hallucinations. “I was aware that I was losing a lot of my own agency; my mind was going. It was very scary. And I isolated so much. I wouldn’t see people – one time I didn’t leave the house for two weeks, taking copious amounts of substances.”

Her friends have since told her it was like watching a speeding train about to derail. “My husband and I, our relationship grows further and further apart, because it’s really difficult for him to be around someone so unwell,” Shah continues. “My best friends, my family … there was nothing anyone could do, bless them. And then in 2022, I decided to take my own life.”

In April of that year, Shah sent a tweet that alarmed many of her followers. “I was a very sick person,” Shah says. “I was scared of going insane and I didn’t think I was ever going to get my full mental capacity back.”

Her cat sitter rushed round to Shah’s house. Later, the singer agreed to go to rehab. It turned out to be “the best thing I ever did”. At first, she was terrified but as soon as she arrived, “I could stop pretending. It was like breathing a sigh of relief.”

She is writing a memoir about her time in rehab because there are so few accounts of it by women. “I was ashamed about being there,” she says. “There was shame in being a woman who was an addict, whereas male musicians might have been revered for it. One of the reasons we can’t get many women into recovery is because of the stigma.” I mention Amy Winehouse; Shah was briefly friends with her. “She was ridiculed so awfully,” says Shah, but “she was an unwell person”.

Shah describes her experience of rehab as “beautiful”. “I don’t think I’ve ever laughed so much in my life as I did in that place,” she says. They had a sports day: “I won every race. People there were so ill they could hardly walk, never mind run.”

It was also liberating to be off social media. “You’re not searching your own name,” she says. “We played parlour games. I did a lot of Zumba. I also learned how to pick locks. There are a lot of criminals in there.”

But many of the people she befriended in rehab are now dead. She pays tribute to them on the single, Twenty Things: “I didn’t realise I was gonna fall in love with everybody,” she says.

On leaving rehab, she felt sturdier. “In the past, I wouldn’t be able to do an interview or a show without having a drink,” she says. “I didn’t realise how difficult I found it to exist within this industry, being quite an awkward, shy person.” Perhaps inevitably, her skin is much thicker now; her marriage has now ended, but she remains friends with her ex. “I don’t sweat the small stuff. I guess that happens when you nearly die. A lot of things that used to bother me don’t any more. I have no issue with people criticising me on the internet.”

The first thing she did when she got out was get back to work. She’d never acted onstage before until September 2022 when she joined a “gleefully anarchic” Shakespeare North Playhouse production of A Midsummer Night’s Dream, playing Titania; but she revelled in her part’s playfulness and earned a nomination at the What’sOnStage awards.

She also finished her fifth album, written with the same playful spirit. Filthy Underneath is a document of Shah’s downward spiral and recovery set to an impeccable groove. It builds on the sonic world of Kitchen Sink but several songs have a wilder rhythmic looseness, recalling the Burundi beat of 80s new wavers Bow Wow Wow, and the gothic exotica of Siouxsie Sioux’s side project the Creatures. Other songs are shot through with 70s influences, such as the Turkish psych of protest singer Selda Bağcan and Indian siren Asha Puthli’s sensual cosmic disco.

The melodies are adventurous, and the contradictions of Shah’s inner psyche loom large, as she confronts her shadow self and ego, and laments the end of her marriage. If that sounds a bit like therapy-speak, lead single Topless Mother takes sardonic aim at some uncomfortable counselling sessions she had during recovery. Its delirious word association (one example: “Sharia, Diana, samosa”) comes off like a playground taunt, as she appears to flip between herself and the voice of her therapist.

Shah uses her vocal range to its fullest, too: there is weightless falsetto and, on the serpentine Food for Fuel, a trill familiar to qawwali, the Arabic-south Asian devotional music style. “I’ve always underplayed my singing, singing in my lower register and not doing too many acrobatics in order to be taken more seriously,” she says. “Whereas actually, I’ve got a big voice.”

It is put to stellar use on Greatest Dancer, a strident goth banger inspired by the time she took some of her mum’s prescription meds in front of an episode of Strictly Come Dancing, and the operatic synthpop ballad Keeping Score – both feel primed for her current shows supporting Depeche Mode in huge arenas. The latter song returns to a familiar theme of hers, toxic relationships, but the subject matter is still raw. “I haven’t worked out how to talk about that one yet,” she says. “It’s about male violence against women, verbal or physical.”

At one point, she was unsure whether she would be able to do this as a job again. But her mum gave her her love of music – especially Scott Walker – and it helps to keep her close: “I am holding the note for her,” as she sings on the deeply moving See My Girl. “I couldn’t give up music because it brings me back to my mam,” she says now. “I’ve got that connection to her, always.”

Another standout is the biting spoken-word sermon of Sad Lads Anonymous, with its wince-worthy depiction of rock bottom. “I’m describing being at an awards show, and my band have left, and I’m still there in a toilet cubicle telling a work experience kid my darkest secrets,” she says. “I look back on this stuff and I’m laughing about a lot of it, but so much of the dumb stuff I did, it was humiliating.” Making Filthy Underneath, Shah thought: “Is this too personal? Is this giving away too much? But I lost my mystery as an artist a long time ago. I’m not gonna get that back, so I might as well just make brutally honest work.”

And there is none more brutally honest than the closing track, the sinister yet wry French Exit, about “sliding off the dancefloor” of life. At first she was apprehensive about showing a song about suicide to Ben Hillier, with whom she makes all her music. But another image springs to mind when she thinks about French Exit now. “We actually used the instrumental of it in A Midsummer Night’s Dream. I have a sexual dance with a donkey to that song.”

Shah hopes to play more live shows, especially abroad; her gigs late last year revealed an artist who seems more liberated, looser and leaning into her new music’s theatricality. Before she gets into the swing of it, she’s excited to head out to LA for the first time, where she intends to visit her friend Mark Lanegan’s grave in the Hollywood Forever Cemetery.

These days Shah is substance-free, “but it’s one of those things with addiction: you can never say never”. There is, though, the small matter of secondhand clothes site Vinted. “I’ve gotten my manager into it as well. I’m an enabler,” she says.

She has been using the app to find clothes such as the black PVC catsuit on Filthy Underneath’s cover, and the Suspiria-ish red dress from punk designer Pam Hogg in the Topless Mother video – in which she rips up a homeware department’s-worth of feather pillows. “I’m really enjoying it this time around,” she says of her hard-won, bedding-shredding creativity. “I don’t know how long this stuff’s gonna last for. So I might as well have fun.”

Filthy Underneath is released on 23 February on EMI North.

In the UK and Ireland, Samaritans can be contacted on freephone 116 123, or email jo@samaritans.org or jo@samaritans.ie. In the US, you can call or text the National Suicide Prevention Lifeline on 988, chat on 988lifeline.org, or text HOME to 741741 to connect with a crisis counsellor. In Australia, the crisis support service Lifeline is 13 11 14. Other international helplines can be found at befrienders.org.