Demi Lovato has said she had three strokes and a heart attack after a drug overdose in 2018, and that doctors told her she had been minutes from death.

The US pop star, 28, says in a new documentary trailer: "My doctors said that I had five to 10 more minutes."

Lovato also told reporters she had been "left with brain damage and I still feel the effects of that".

Those effects include blurry vision that means she can't drive and made reading difficult, she revealed.

The former child star was taken to hospital in July 2018 after being found unconscious at her Los Angeles home. The overdose, reportedly of opioids laced with fentanyl, came a month after she revealed she had broken six years of sobriety.

In the trailer for her new YouTube documentary series Dancing With The Devil, she says: "I've had a lot of lives, like a cat. I'm on my ninth life."

Speaking to journalists on Wednesday, she revealed the lasting effects. "I don't drive a car because I have blind spots in my vision," she said.

"For a long time, I had a really hard time reading. It was a big deal when I was able to read a book, which was like two months later, because my vision was so blurry."

She said she was releasing the documentary "to help people who have been on the same path as I have", adding: "I wanted to set the record straight, and I wanted to reveal it all for my fans."

Lovato was a child actor on Barney and Friends and found wider fame on the Disney Channel as a teenager. She starred in its hugely popular Camp Rock film series before launching a successful solo music career.

She has released six studio albums and has appeared as a judge on the US version of The X Factor. Her hits include Sorry Not Sorry and Skyscraper, and she topped the UK chart in May 2018 with Solo, her collaboration with Clean Bandit.

The following month, she released a song titled Sober, in which she revealed: "I'm not sober any more." The overdose came weeks later.

Lovato has been open about her struggles with mental health and addiction throughout her career.

In a 2012 documentary Stay Strong, she spoke of her "daily battle" with eating disorders, self-harm and mental health issues, as well as addiction. She talked about the extent of her substance abuse during her teenage years in another documentary in 2017.

"One of the main reasons I'm coming forward is so I never have to live that life again," Lovato said on Wednesday, according to the Associated Press.

Lovato re-launched her singing career at last year's Grammy Awards and sang the national anthem at the 2020 Super Bowl.

Last month, she sang on a TV special marking US President Joe Biden's inauguration. Dancing With The Devil is due to be released on YouTube on 23 March.