Miley Cyrus has responded to Sinead O'Connor's open letter warning her not to let the music industry make a "prostitute" out of her, NME reports. Writing on Twitter, Cyrus compared O'Connor - who has openly battled with mental health issues - to the actress Amanda Bynes, who was hospitalised after a mental breakdown earlier this year. "Before Amanda Bynes ... There was..." she posts before an image of Tweets sent previously by O'Connor asking for psychiatric help. She then posted a follow-up image of Sinead O'Connor's controversial Saturday Night Live appearance from 1992 during which she tore up a photo of Pope John Paul II. O'Connor wrote an open letter to Cyrus after the pop-star cited the Irish singer as an inspiration for her explicit video "Wrecking Ball," in which she swings naked from a metal demolition ball. The video followed her controversial performance at the MTV VMAs during which she twerked for "Blurred Lines" singer Robin Thicke. In a letter published on her website (via the BBC), O'Connor writes that she was propelled to write the letter "in the spirit of motherliness" after "dodging phone calls from various newspapers" who wanted her to speak about Cyrus' comments. "Nothing but harm will come in the long run, from allowing yourself to be exploited," she writes. "Please, in future, say no when you are asked to prostitute yourself." "I am happy to hear I am somewhat of a role model for you and I hope that because of that you will pay close attention to what I am telling you," she continues. "I am extremely concerned for you that those around you have led you to believe, or encouraged you in your own belief, that it is in any way 'cool' to be naked and licking sledgehammers in your videos. It is in fact the case that you will obscure your talent by allowing yourself to be pimped, whether it's the music business or yourself doing the pimping."