The article focuses on a study by Drs Ryan McKay and Lisa Cipolotti on a patient named ‘LU’ who presented with the delusion when being assessed for the impact of severe epilepsy caused by a viral brain infection.
They describe the case in their paper:
At neuropsychological assessment LU presented with the Cotard delusion. She repeatedly stated that she was dead and was adamant that she had died two weeks prior to the assessment (i.e. around the time of her admission on 19/11/2004). She was extremely distressed and tearful as she related these beliefs, and was very anxious to learn whether or not the hospital she was in, was “heaven”. When asked how she thought she had died, LU replied “I don‚Äôt know how. Now I know that I had a flu and came here on 19th November. Maybe I died of the flu.” Interestingly, LU also reported that she felt “a bit strange towards my boyfriend. I cannot kiss him, it feels strange ‚Äî although I know that he loves me.” Other presenting symptoms included reported sensations of dizziness, as well as musical hallucinosis (hallucinations of disco music), tactile hallucinations (a feeling of running water on her left forearm) and visual hallucinations (moving walls).
The study tested theories which suggest it is caused by trying to make sense of losing automatic emotional responses to familiar people – a consequence of the brain damage.
Some researchers have argued that this is the basis of a similarly curious syndrome, known as Capgras delusion, where someone believes that their friend, spouse or relative has been replaced by a near-identical looking impostor.
In Capgras delusion, it is thought that the same problem with automatic emotional response is present, but that the person attributes the problem to external changes in the world (“it’s something to do with my wife…”) and reasoning problems lead to the delusion itself (“…and she’s been replaced by an impostor”).
In contrast, one theory of Cotard delusion is that it might be partly caused by the same emotional response impairment, but where the person attributes it to an internal change (“it’s a problem with me…”) with reasoning problems leading to the delusional belief (“…and the problem is, I’m dead”).
So far, this has only been an educated guess by researchers and has never been tested.
McKay and Cipolotti assessed whether LU typically made internal or external attributions for negative events, and found, consistent with the existing hypothesis, that she made consistent internal attributions.
One unexplained part, both in this study, and in delusions in general, is why these unusual experiences and odd attributions lead to delusions, and not simply to confusion (e.g. “people feel strange, I think it’s a problem with me, but and I don’t know what to make of it”).
It is thought that reasoning problems or cognitive biases are involved, most likely caused by damage or disturbance to the right hemisphere of the brain.
However, there is still little conclusive evidence for the very striking reasoning errors you might expect with such strikingly unusual delusions.