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Why people have delusions

Teresa Tanoos's picture
Familiar and unfamiliar feelings can prompt delusions

A delusion is a belief that is not true. When a person maintains an irrational belief, even in the face of evidence to the contrary, they are called delusional. Delusional disorder is a psychiatric illness that applies to people who maintain false beliefs that involve situations that could potentially occur in real life.

People with delusional disorder do not necessarily appear odd or bizarre. They typically do not have any accompanying hallucinations or other apparent thought, mood or mental disorders, so aside from their fixed false beliefs, they can usually socialize and function like any other normal person. However, their preoccupation with delusional ideas can interfere with their lives.

A new study, published in the journal Frontiers in Psychology, attempts to explain why delusional people cannot shake their false beliefs. Study author Professor Phillip Gerrans, from the University of Adelaide in Australia, says that it has to do with faulty “reality testing”.

Just like dreams, Prof. Gerrans believes that delusions are due to faulty reality testing in the brain. Reality testing, he explained, keeps track of a "story telling" process in the cognitive regions of the brain, where a narrative of a person's experience is generated.

To further illustrate the concept of reality testing, he used the example of a person with a headache who automatically believes it could be a brain tumor, but then quickly rejects such belief as irrational.

In someone who has faulty reality testing, however, Prof. Gerrans explained that they would continue to believe their initial thought that the headache was due to a brain tumor – and even embellish upon it to such an extent that they actually believe the headache is a threat to their life or to others.

According to Prof. Gerrans, familiar and unfamiliar feelings can trigger delusions, so he focused his study on delusions that can be prompted by both of these contrasting feelings.

One delusion that can be prompted by familiar and unfamiliar feelings is referred to as the "Capgras delusion", which is the delusion of "doubles”. As an example of this kind of “doubles” delusion, Gerrans wrote about a man with a severe head injury who spent a full year in the hospital. Upon his return home, he recognized his family’s faces, but believed they were all impostors.

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For the man with the head injury, the story in his brain made sense “no matter how much people tried to point out that his family was the same,” Gerrans explained. Nevertheless, in this man’s mind, all of his family members had been replaced by impostors.

Another delusion that can be prompted by familiar and unfamiliar feelings is known as the "Fregoli delusion", which occurs when an individual thinks a familiar person is following them in disguise. This kind of delusion allows a person to cope with a familiar feeling prompted by seeing a stranger, Gerrans explained.

He added that individuals are able to experience both familiar and unfamiliar feelings during situations that are more familiar to them.

Take the feeling of déjà vu, for example, which is a sense that makes you feel as if something familiar that you’ve experienced before is happening again. However, Gerrans says that such déjà vu feelings “do not lead to delusion in people whose reality testing is intact."

So how could Prof. Gerrans’ study help people suffering from delusional disorders?

The answer, according to him, is that the study helps explain what reality testing is; thus, leading to a better understanding of its role in delusional thinking, which could lead to improved outcomes for people suffering from delusional disorder.

What will likely not help, he says, is telling the truth to a person experiencing a delusion. Prof. Gerrans says that’s why new strategies need to be developed for helping people with delusional disorder.

Accordingly, Gerrans says that the goal of his work is to continue explaining what reality testing is, and how it can contribute to delusional thinking, so as to help those with delusions deal with them in such a way that they “no longer adversely affect their lives."

Mental disorders can and do adversely affect people's lives. Indeed, according to a recent study, nearly 20% of children in the U.S. suffer from mental illness, and that percentage has been increasing for over a decade. To learn more, click here.

SOURCE: Frontiers in Psychology, Pathologies of hyperfamiliarity in dreams, delusions and déjà vu, Phillip Gerrans, published February 20, 2014 (doi: 10.3389/fpsyg.2014.00097)