What are delusions versus hallucinations?

Delusions and hallucinations have different types of symptoms, says Jeffrey Lieberman, MD, director, New York State Psychiatric Institute. He discusses how they differ.

Transcript

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Woman in Texas who killed her children believed that they were essentially

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agents of the devil. [MUSIC PLAYING]

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There are different types of symptoms. Delusions are basically cognitive disturbances

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where people's ideas and beliefs become distorted and not based in reality.

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You know, somebody thinks their neighbors are listening to them through their walls or that their teachers at school

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dislike them and are failing them or giving them bad grades or that the CIA is bugging their home.

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And these are strange ideas or false ideas that people have complete conviction in.

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They can't be talked out of it. You can show them all the evidence you want. You can tell them about the implausibility, and they can't be talked out of them.

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They're incorrigible. Whereas hallucinations are essentially perceptual abnormalities. That is, you hear things, and it usually

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comes in the form of voices. And there's no external stimulus that's producing the voice. You may see things.

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You may smell things. You may feel things. But there's no stimulus that's really producing it. The hallucinations and the delusions

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are particularly problematic, not just for the individual but for society, because when we have these--

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as we're having now, increasingly and repeatedly-- these violent incidents, these civilian massacres that make no sense, to the extent

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that they involve perpetrators who have untreated mental illness, they're occurring because these people's delusions are

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telling them to do this or making them think they have to do this. Andrea Yates, for example, woman in Texas

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who killed her children, believed that they were essentially agents of the devil

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and she had to kill them to rid them from humanity. Other people are listening to the voices.

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The voices say these people that are coming towards you are going to attack you. You have to kill them first. And you'll find that people will act on these.

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And, you know, it's not a crime of passion. They're not robbing somebody. They're killing somebody they have no relation to

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and no reason to because of-- they're being impelled by their symptoms. [AUDIO LOGO]