The New York City medical examiner said he had committed suicide.
A New York native, Vizzini began writing for publications including the New York Times and the New Yorker while he was still a teenager. His 2006 book, It's Kind of a Funny Story, was a semi-autobiographical tale about a high school student who ends up in a mental hospital after attempting suicide and became a 2010 movie starring Zach Galifianakis and Emma Roberts.
Vizzini wrote several other young adult novels, including Be More Chill and The Other Normals, as well as the middle school-grade series House of Secrets, which he co-wrote with director Chris Columbus (Home Alone).
Vizzini is survived by his wife, Sabra, and a son.