In December 2016, Heather B Armstrong phoned her mother from her kitchen floor in tears and told her that she wanted to be dead. With her children thousands of miles away spending Christmas with their father, Armstrong’s ex-husband, and having been abandoned by a date, the blogger-turned-author was alone at home when she felt “overcome with a really bad feeling”.

It was not the first time that she had made such a call, but this felt different. “It’s the night that I called her and I said I don’t feel like I can hold on any more,” says Armstrong, 43, whose website Dooce once earned her the title “queen of the mommy bloggers”.

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Her mother kept her on the phone for 40 minutes while she rushed to her daughter’s home in Salt Lake City and stayed the night to take care of her. The following morning she forced Armstrong, who had been suffering from severe depression for a year and a half, to book an appointment with her psychiatrist – a call that within months would end up transforming her life.

Just a few months later she was taking part in a pioneering world-first study that would plunge her into a deep sleep that would help relieve her depression within weeks.

Today Armstrong, who has documented her experiences with depression in the new book The Valedictorian of Being Dead: The True Story of Dying Ten Times to Live, credits her mother’s actions with saving her life. “I didn’t overtly want someone to intervene, but I think subconsciously I knew that if I didn’t reach out and have someone do it that this was going to destroy me. And she knew that,” she says matter-of-factly.

Over breakfast at her hotel in New York, where she is joined by her partner, Pete Ashdown, for moral support, she says she can trace her first experiences of depression back to high school, when she remembers a teacher shaking her shoulders and telling her: “You’ve got to let go.” She first started taking antidepressants in college, when she had a breakdown during her sophomore year, and was hospitalised after experiencing suicidal feelings following the birth of her first child.

The most recent started while training for the Boston Marathon. She thought her gruelling training regime was the cause of her sadness, but when the race was over she realised it was something else.

She was so anxious that she couldn’t sleep or stop worrying about simple day-to-day tasks. “It was a state of panic that I lived in for 18 months. Constant state of fire. Fiery panic,” she says. Most of the time Armstrong, who is dressed in a black suit and her earlobes decorated with little gold bull head studs, speaks with remarkable composure and steady eye contact. But now her voice trembles and she looks up to the ceiling as if holding back tears. “Yeah. Which I wanted to end. I thought, if I’m dead then I don’t have to feel this fire any more. I’m not going to be dead, but wouldn’t that be great? Wouldn’t that be great?” After a pause, she adds: ”I’m so glad I don’t feel that way any more.”

Unlike previous life experiences (such as postpartum depression, leaving Mormonism and work – which in 2002 got her fired) which she has often written publicly about in real time on Dooce, she was frightened to talk to anyone apart from her mother about it for fear of losing custody of her two daughters, Leta, 15, and Marlo, nine.

It also put her off seeing her psychiatrist until her mother’s intervention left her with no option. When, in February 2017, she finally saw him, he suggested she take part in a pilot study at the University of Utah into the potential antidepressant effect of general anaesthetic Propofol. For the first time in over a year she felt optimistic.

I was just so devoid of caring because all of my energy was consumed by worry Heather B Armstrong

But as only the third person in the world to undergo the treatment, was she not scared? “Oh, I didn’t feel anything at that point … you could have dropped me out of a plane and I wouldn’t have flinched,” she says. “I was just so devoid of caring because all of my energy was consumed by worry, of how do I unload the dishwasher, how do I fold clothes. It sounds so stupid … it’s not a woe is me situation, it’s just the day-to-day was so overwhelming and unrelenting that I didn’t know how to escape it.”

The following month she started going into hospital three times a week to be put into a deep state of anaesthesia (although, according to Dr Brian Mickey, who ran the study, not close to death, as her book suggests) for 15 minutes to see if it had an antidepressant effect. While she slept, doctors monitored her brain’s “burst suppression”, an electrical pattern formed of a flatline interrupted by bursts every few seconds, before waking her up again.

For the first four of the 10 treatments she felt the same, but after the fifth she felt dramatically different. “I just walked into my house and wanted to sort of, like, dance,” she laughs. “It was a very strange feeling because I wasn’t tired, I was ready to go. I had put on makeup that day, I had brushed my hair, taken a shower and I thought: ‘I want to go out!’ which was a very strange sensation.” The next morning, she awoke without her usual anxiety and felt like “something had switched in my brain”.

Of the 10 people who took part, Armstrong was one of six for whom their depression score decreased by 50% or more. Mickey, associate professor of psychiatry at the university, says they don’t yet know how it works, but adds: “We know that there’s definitely evidence that modulation of Gaba (gamma-Aminobutyric acid) and glutamate, these neurotransmitters in the brain, in some cases can trigger an antidepressant response. So because Propofol works on Gaba and glutamate systems, we suspect that that could be a mechanism.”

Further trials are needed, he says, but if it is found to be effective, it could provide an alternative to electroconvulsive therapy, which he claims is effective but for many people the procedure, which uses electric current to induce short seizures, comes with side-effects such as memory loss.

Two years on from being treated with Propofol, Armstrong says she continues to take medication but no longer feels like anything is insurmountable. “I just don’t ever have the feeling like, ‘I can’t do this.’ I don’t ever have that thought, which was the defining factor of my life for 18 months.” She started seeing Ashdown, 52, president and founder of internet provider XMission, a few months after her treatment. In August, Armstrong and her daughters moved in with him and his 13-year-old daughter.

Her memoir, she hopes, will provide others with a language to talk about mental health and raise awareness of the study. While she has received positive messages from fans online, she says she is still anxiously waiting for the verdict of her father, who she writes frankly about in the book.

After over a decade of posting regularly on her site, she took a step back from blogging in 2015, declaring the way it had been monetised by brands a “health hazard”. She has since returned to her blog, but now she says she works with companies on her own terms.

Next she plans to focus her attentions on removing the stigma around mental health and improving services, especially for children. “My brother’s son goes to a high school where last year there was six suicides. Six. Something’s going on and we’re not addressing it. We’re not funding it, there’s no money in it and it’s a disaster.” She wants to see more insurance companies covering mental health and seminars and free counseling in high schools. “If the family can’t afford $130 an hour where does that kid go? We need to overhaul the complete system, and Utah’s the perfect place to start.”