delusion

n. A fixed false belief. Delusions are beliefs that are held with absolute certainty in spite of any evidence to the contrary. Delusions can be nonbizarre (e.g., believing the CIA or FBI is following you) or bizarre (e.g., believing that aliens are harvesting your organs while you sleep). In both cases the individual is not at all open to alternate explanations, no matter how compelling they may be (e.g., confirmation from the authorities that they are not keeping a file on you; a CT or MRI scan indicating all organs are intact and functioning well). Delusions are most commonly found in individuals with psychotic disorders such as schizophrenia but can also occur in severe cases of bipolar disorder, major depressive disorder, and stimulant abuse and dependence.

- DGa