The singer, 55, said she was going to the hospital Thursday after posting a lengthy message on Twitter earlier that day saying she had "decided to follow [her] son."
In a Thursday morning tweet, the "Nothing Compares 2 U" singer wrote, "There is no point living without him," referring to her son, Shane O'Connor. "Everything I touch, I ruin. I only stayed for him. And now he's gone. I've destroyed my family. My kids don't want to know me."
HGL/GC Sinéad O'Connor in 2019
In a follow-up tweet she shared late Thursday, Sinéad apologized, writing, "I'm sorry. I shouldn't have said that. I am with cops now on way to hospital."
She continued, "I'm sorry I upset everyone. I am lost without my kid and I hate myself. Hospital will help a while. But I'm going to find Shane. This is just a delay."
Sinéad first shared the news of her son's death Jan. 7. Shane, who was 17, died after going missing, Sinéad posted on Twitter last week.
"My beautiful son, Nevi'im Nesta Ali Shane O'Connor, the very light of my life, decided to end his earthly struggle today and is now with God," Sinéad wrote at the time. "May he rest in peace and may no one follow his example. My baby. I love you so much. Please be at peace."
Sinéad shared Shane with musician Dónal Lunny. She is also mom to three other children: Jake, Roisin and Yeshua.
Sinéad's hospitalization comes after years of mental health struggles. Recounting her traumatic childhood, she told PEOPLE in May 2021 that she had been diagnosed with bipolar disorder, complex post-traumatic stress disorder and borderline personality disorder.
In 2015, she underwent a radical hysterectomy to treat endometriosis, and was "triggered" following the surgery, she said. She later spent time in psychiatric facilities following the procedure.
After the procedure, O'Connor would sometimes post alarming cries for help on social media ("I have taken an overdose," she announced on Facebook in 2015).
"I was mental," she admitted, referring to her struggles with mental illness. "But I don't regret those 'embarrassing' videos. I'm quite proud, in a weird way, that I was that open ... The nature of a singer is to be emotionally honest. I've always been pretty open. And I have no regrets."
Today, O'Connor has biweekly check-ins with her medical team.
"You can never predict what might trigger the [PTSD]. I describe myself as a rescue dog: I'm fine until you put me in a situation that even slightly smells like any of the trauma I went through, then I flip my lid," she says. "I manage very well because I've been taught brilliant skills. There was a lot of therapy. It's about focusing on the things that bring you peace as opposed to what makes you feel unstable."
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Sinéad postponed scheduled shows in November 2020 as she sought help for addiction and trauma, she shared on Twitter at the time.
"I had a very traumatic six years and this year was the end of it but now recovery starts," she wrote in a since-deleted tweet, adding, "This year I lost someone beloved and has affected me so badly that I became briefly addicted to a drug other than weed."
Sinéad said she "grew up with a lot of trauma and abuse. I then went straight into the music business. And never learned really how to make a normal life … Never took proper time to heal. Wasn't ready to either."
The singer said entering treatment was a "step toward making a life I am happy in."
"If taking this step means my career is over then so be it. As Mary Oliver says, I must save the only life I can," she wrote.
If you or someone you know needs mental health help, text "STRENGTH" to the Crisis Text Line at 741-741 to be connected to a certified crisis counselor.
If you or someone you know is considering suicide, please contact the National Suicide Prevention Lifeline at 1-800-273-TALK (8255), text "STRENGTH" to the Crisis Text Line at 741-741 or go to suicidepreventionlifeline.org.