Which term describes a false belief that is firmly held despite evidence to the contrary?

The term that describes a false belief firmly held despite evidence to the contrary is delusion. Delusions are a symptom commonly associated with various psychiatric disorders, including schizophrenia, delusional disorder, and severe depression. They are characterized by a disconnect from reality where the individual remains convinced of their false belief even when presented with contradictory evidence.

In contrast, an illusion typically involves a misinterpretation of a real external stimulus, such as mistaking a shadow for someone’s figure, rather than a firmly held false belief. Hallucinations involve perceiving something that isn't present at all, like hearing voices when no one is speaking, and are more related to sensory experiences than cognitive beliefs. Derealization refers to the feeling that the surrounding world is not real or is distant, which does not involve the same cognitive assertions about reality or the firm belief in false information. Understanding these distinctions clarifies why the concept of delusion specifically captures the nature of false beliefs associated with mental health conditions.