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Demi Lovato's mother Dianna De La Garza has said the 26-year-old singer has now been sober for 90 days.

Speaking to radio station Sirius XM, De La Garza said she "couldn't be more thankful or more proud of her".

Lovato was taken to hospital in July for an apparent drug overdose and has been in rehab since her release.

De La Garza added: "Addiction being a disease, it's work. It's very hard. It's not easy, and there are no shortcuts."

Her mother added that she "can't really say for sure" what led Lovato, who has struggled with substance abuse throughout her career, to relapse.

The star released the song Sober in June, which was about her no longer being sober.

In the interview, De La Garza said: "I knew that she wasn't sober," but added: "I didn't know what she was doing because she doesn't live with me and she's 26."

She also added that she found out about Lovato's overdose after receiving text messages asking what had happened.

"The one text message that clued me in on what was going on said, 'I just saw on TMZ and I'm so sorry,'" she said.

"Before I could get to TMZ, I got the phone call from her assistant and she said, 'We're at the hospital.' So then I knew, OK, she's not gone. She's here. And I said, 'What's going on?' And the words that I heard are just a nightmare for any parent: 'Demi overdosed.'"

The singer has been absent from social media and the public eye since the incident, only posting a

"I now need time to heal and focus on my sobriety and road to recovery," she wrote.

"The love you have all shown me will never be forgotten and I look forward to the day where I can say I came out on the other side. I will keep fighting."

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