It's round four of a week-long exchange between Sinead O'Connor and Miley Cyrus, with the former penning a new and lengthy letter claiming that the pop singer's actions have led cyber-bullies to urge her to commit suicide.

O'Connor spends a great deal of the 1,770-word letter addressing the dangers in mocking sufferers of mental health problems and repeatedly calls on Cyrus to apologize to both herself as well as actress Amanda Bynes, whom Cyrus referenced in earlier Twitter posts.

"As a result of what you did I have had numerous communications from people urging me to commit suicide," she writes. "Not to mention I have been the subject of literally thousands of abusive articles and or comments left after articles, which state that I and therefore all perceived mentally ill people, should be bullied and be invalidated."

The mother of four says that her children's lives "would be destroyed if I were to buckle under the abuse you set me up for." She says that were it not for her kids and her personal strength, "these types of communications and these types of articles and remarks could have had their desired effect."

O'Connor started this conversation with Cyrus in a first open letter posted on her website last week. In it, she urged the pop singer to focus on her musical talent rather than her sexuality. Cyrus responded by mocking O'Connor on Twitter, pointing to her mental health struggles of two years ago. O'Connor penned two more letters, forcefully calling Cyrus' attitude "dangerous" and demanding an apology.

Cyrus passed on the opportunity to address the controversy on "Saturday Night Live" over the weekend, but was then asked about it by Matt Lauer on the "Today" show on Monday (Oct. 7). "I don't know how someone can start a fight with somebody that's saying, 'Hey I really respect you and I really love what you did.' 'You know what? You suck!' And that was kind of crazy," she told Lauer, adding that she's a "big fan" of the Irish singer. "It's all good. You can write as many open letters as you want. That's really what blogging is. I get open letters every day; it's nothing too new for me."

Unsurprisingly, Cyrus' use of the word "crazy" did not sit well with O'Connor. "You may have noticed that in your country it is the fashion to lynch young famous ladies in the streets because they have been diagnosed crazy by media and or celebrities," she writes. "This is an unacceptable breach of human rights. And at some point the media may attempt it upon you. If so they will certainly have to deal with me."

Later, O'Connor also repeats her call for Cyrus to also apologize for publicizing two-year-old tweets when "I was unwell" in a way that made them appear recent. "I am very fit for work," she explains. I have four children to support. I can’t do that if people believe me to be unemployable."

She adds, "I doubt you thought clearly before doing what you did and I’m willing to give you the benefit of doubt on that, as I’d find it hard to believe someone so young could be that calculatedly evil to anyone, never mind someone who did absolutely nothing to deserve such abuse, or to be set up for such abuse from others."