What mental disorder do you have when you believe something that is not true?

Believing something that is not true can be associated with several mental disorders, but it is particularly indicative of delusional disorder or certain types of schizophrenia. In these cases, individuals may hold strong beliefs (delusions) that are not based in reality, despite evidence to the contrary. Other conditions, such as Bipolar disorder or severe depression, can also involve delusions during episodes of mood disturbance. It's important for individuals experiencing these symptoms to seek professional evaluation and support.