Difference Between Hallucination and Delusion

In the past few years, a number of diseases have been diagnosed that are related to mental conditions and the perceptions of people related to society’s norms or beliefs.


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These diseases or disorders are highly researched in the past years, and multiple reasons behind them and their cures have been found to some extent. 

Similar to this kind, two such disorders are having hallucinations and delusions.

While both of these are presumed with the perception of one’s brain, these two are considerably different from one another and carry a lot of differences.

Hallucination vs Delusion 

Hallucinations are sensory experiences that occur in the absence of any external stimuli. They can involve any of the five senses (sight, sound, smell, taste, and touch). Delusions are false beliefs that are not based in reality and are not subject to change even when presented with evidence to the contrary.

Hallucination vs Delusion

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Hallucination as a state is more of a thing inside the brain of a person rather than existing in the external environment.

When a person is said to suffer from hallucination, it implies that the person feels, listens, or sees particular things which do not exist in reality.  

But on the contrary, Delusion happens to be slightly different. Rather than a thing related to the senses of a person, it refers to the belief of a person related to a particular thing.

It is called Delusion when the belief stands in a particular place that is completely against the actual reality.

Comparison Table

Parameters of Comparison Hallucination   Delusion 
Meaning  State of a person in which he believes certain sensory changes taking place near him. State of a person in which he believes a false reality. 
Causes  Happens due to lack of sleep, influence of alcohol or influence of drugs, etc. Happens due to certain psychological conditions such as depression.  
Symptoms  The affected person might hear sounds or see things. The affected person will believe something untrue and sound bizarre to other people. 
Treatment  It can be treated by way of medication alone. It will need medication along with therapy. 
Affects Senses of a person Believes of a person. 
Example  Hearing footsteps even when no one is walking. Believing someone is talking behind your back even if he is not. 

What is Hallucination? 

Hallucination can be explained as the neurological or psychological condition belonging to a person in which the person believes that his senses are sensing a certain thing that does not exist in reality in front of the other people.

There are many reasons behind this situation, and most of them are not because of any mental illness or psychological disorder. 

As per the research that has been conducted till today, it has been concluded that hallucinations can be caused by many factors, and some of the most popular ones are the lack of sleep, the influence of any drug, the influence of medicine, or the influence of alcohol, etc.

All these things play a kind of mind game with the person and make him believe that a particular thing is happening around him even when it is not. 

This can be better explained by way of an example- suppose a person hears footsteps even when no one is walking around him.

This is called a hallucination because it affects the hearing sense of that person and makes him believe that someone is walking even when someone is not. 


What is Delusion? 

Talking about Delusion as an underlying state in a person, it can better be explained by the beliefs of that particular person.

Delusion is not some kind of illness but more of the perception of a person where a person believes the occurring of certain event which is not happening in the real world and the unique feature about this state is that even if we present evidence to the person telling him that what he believes is not true, he is not going to change his perception. 

As per the experts in the related field, delusion is caused due to certain neurological situations such as anxiety, or depression, or violent childhood, etc.

When a person suffers from any of these conditions, he makes perceptions about people which are not true, but he believes them to be true based on his past experiences.  

An example can be of a person who believes that his mother is feeding drugs to him by way of the meal, although there is enough evidence that no such thing is happening.

One important thing about Delusion is that despite any effort done in the right direction, the belief of the person can hardly be changed. 


Main Differences Between Hallucination and Delusion 

  1. Hallucination is caused when there is a hindrance in the sensory perception of a person, but delusion is caused when there is a hindrance in the perception of reality related to a person. 
  2. Hallucination is caused by factors like lack of sleep or the influence of alcohol, while delusion is caused by certain mental illnesses such as depression or anxiety. 
  3. To treat hallucination, certain medications are required, but to treat delusion, medication along with therapy is required. 
  4. Hallucination affects the senses of a person, while delusion affects the beliefs of a person. 
  5. An example of hallucination is hearing bell sounds even when no one is making any such sound, and an example of Delusion is believing that a person is plotting against us even when he’s not. 
Difference Between Hallucination and Delusion


  1. https://www.sciencedirect.com/science/article/pii/S0165178108002217
  2. https://www.sciencedirect.com/science/article/pii/S0920996497000492
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