Steve Granitz / WireImage 1 / 16
Steve Granitz / WireImage 1 / 16

Demi Lovato has hit back at Internet bullies who make nasty comments about her online, calling them "sick in the head" and "born without a heart."

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The Disney singer/actress has been open about her past experiences with childhood bullying and she launched into a Twitter rant on Monday to call out users who have been posting spiteful remarks online.

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Lovato, who recently received treatment for an eating disorder and self-harming, writes in a series of posts, "It really surprises me the hateful things people say on the internet... After all the awareness of cyber-bullying... I mean wow."

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"So sad... Praying for all the people in the world who feel it's okay to bully people over the internet because if you are one of those people, then... You must have had something really terrible happen to your childhood or you're really sick in the head. Must suck to be born without a heart."