Published Monday, 23 April 2012
The Irish star, who has been open in the past about her battles with mental illness, briefly posted a statement on her website over the weekend, urging fans not to show up for the German show and she has since announced her plans to retreat from the music industry and work "a normal job".
All messages posted to her personal website have since been removed and the site itself has been replaced by a white space.
In a tweet to fans late last week, O'Connor wrote, "Am going home and cancelling touring for the year. Doc had asked me not to tour but I thought was stronger than am."
Her Twitter.com account has been taken offline.
A message O'Connor sent to fans before her website was shut down has since been re-posted on a fansite. It reads: "With enormous regret I must announce that I have to cancel all touring for the year as am very unwell due to bi polar disorder.
"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. So very stupidly I ignored his advice to my great detriment, attempting to be stronger than I actually am."
O'Connor concluded that she hoped to be well enough to appear at a Curtis Mayfield tribute concert in New York in July.
Ironically, the singer's announcement came just hours after dates were added on her North American tour.
Live Nation Canada promoters have confirmed the shows have been cancelled.
O'Connor made headlines at the beginning of the year when she split from husband Barry Herridge just two weeks after the couple wed in Las Vegas.
She was subsequently hospitalised to treat her depression following a public meltdown on Twitter.com in which she pleaded for help and revealed she had taken an overdose of pills.
O'Connor closed her Twitter account after the incident, but was soon back online, revealing she had reunited with Herridge.