Now, experts describe schizophrenia as a spectrum disorder that includes all the previous subtypes ... Seeing or hearing things that aren't there. Delusions: Mistaken but firmly held beliefs ...

Beliefs remain fundamental to our behavior and identity, but are not well understood. Delusions, on the other hand, are fixed, usually false, beliefs that are strongly held, but not widely shared.

Under the older definition, people with undifferentiated schizophrenia exhibit symptoms of more than one type of ...