The Nothing Compares 2 U singer raised red flags last year with her bizarre Twitter rants where she spoke of suicide and depression, and then married Barry Herridge in December, split up with him, and then got back together.
"With enormous regret I must announce that I have to cancel all touring for the year as am very unwell due to bipolar disorder," Sinead announced on her official website.
"As you all know I had a very serious breakdown between December and March and I had been advised by my doctor not to go on tour but didn't want to 'fail' or let anyone down as the tour was already booked to coincide with album release."
Sinead, 45, admits she should have listened to her doctor.
"So very stupidly I ignored his advice to my great detriment, attempting to be stronger than I actually am," she wrote.
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"I apologise sincerely for any difficulties this may cause. While touring will be cancelled I do hope and plan to appear at the Curtis Mayfield tribute in The Lincoln Centre in July."
Sinead's latest album, How About I Be Me (And You Be You) was released in February and received positive feedback.