Nihilistic delusions are persistent beliefs that a subject does not exist or is dead. Like other delusions, these beliefs endure even when patients are presented with information that contradicts them, such as a recognition from a third party that the patient is alive and appears to exist. This psychological phenomenon was first described in the 19th century by Jules Cotard, a French researcher, and is sometimes known as a Cotard delusion in reference to this. It can be observed in patients with certain mental health conditions as well as people with brain injuries.
Patients with nihilistic delusions may express them in several different ways. Some patients simply believe they themselves do not exist, and in some cases, have never existed. They do not recognize information that invalidates this claim and may think they are invisible or inaudible to the people around them. Others think they are dead, and some experience vivid hallucinations to accompany the delusion, believing they are rotting corpses, for example, or thinking that limbs are missing.
If a care provider questions the patient, he or she may often reveal no personal information. Patients who think they do not exist believe they have no names, ages, or parents, for example. They may not recall anything from their past. Those who believe they are dead may tell care providers how they died and could offer information about their lives.
Cotard believed that nihilistic delusions were the result of “negativism.” The actual psychology behind them may be somewhat more complex. Patients with conditions like schizophrenia, bipolar disorder, and borderline personality disorder can develop a feeling of disconnect from the world around them. This may manifest in the form of delusions which seem quite logical to the patient, even if they appear bizarre to bystanders. Thus, a patient may develop nihilistic delusions after being ignored or silenced, in an attempt to explain those experiences.
In the case of brain injuries, the delusions can be the result of damage to parts of the brain involved in self perception. Such patients can be challenging to treat, as they may not respond to therapy and medications in the same way that those who have mental illnesses do, because the problems with the brain are very different. After an injury, the brain can gradually remap connections and build new associations, but this could take time. During this process, the patient may need supportive care to perform tasks of daily living and slowly erode these delusions.