Sinead O'Connor canceled her 2012 tour due to a bipolar disorder.

The singer said that she is "very unwell" and was adviced by her doctor to not do the concerts after her "very serious breakdown between December and March," according to a post on her website.

Bipolar disorder is a condition in which people experience quick "mood swings" meaning they go back and forth between periods of a very good or irritable mood and depression.

O'Connor, 45, recently divorced from therapist Barry Herridge after 16 days of marriage.

She is best known for her 90's hit "Nothing Compares 2 U."

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