Cotard syndrome...

Cotard delusion is a rare condition marked by the false belief that you or your body parts are dead, dying, or don't exist. It usually occurs with severe depression and some psychotic disorders. It can accompany other mental illnesses and neurological conditions. You might also hear it referred to as walking corpse syndrome, Cotard's syndrome, or nihilistic delusion.

Researchers aren't sure what causes Cotard delusion, but there are a few possible risk factors. several studies indicated that the average age of people with Cotard delusion is about 50. It can also occur in children and teenagers. People under the age of 25 with Cotard delusion tend to also have bipolar depressions. Women also seem to be more likely to develop Cotard delusion.

In addition, Cotard delusion seems to occur more often in people who think their personal characteristics, rather than their environment, cause their behavior. People who believe that their environment causes their behavior are more likely to have a related condition called capgras syndrome. This syndrome causes people to think their family and friends have been replaced by imposters. Cotard delusion and Capgras syndrome can also appear together.