Hallucinations are false or distorted sensory experiences that appear to be veridical perceptions. These sensory impressions are generated by the mind rather than by any external stimuli, and may be seen, heard, felt, and even smelled or tasted.

A delusion is a false belief based on incorrect inference about external reality that is firmly sustained despite what almost everybody else believes and despite what constitutes incontrovertible and obvious proof or evidence to the contrary. The belief is not one ordinarily accepted by other members of the person's culture or subculture (e.g., it is not an article of religious faith).

A hallucination occurs when environmental, emotional, or physical factors such as stress, medication, extreme fatigue, or mental illness cause the mechanism within the brain that helps to distinguish conscious perceptions from internal, memory-based perceptions to misfire. As a result, hallucinations occur during periods of consciousness. They can appear in the form of visions, voices or sounds, tactile feelings (known as haptic hallucinations), smells, or tastes.

Delusions are a common symptom of several mood and personality-related mental illnesses, including schizoaffective disorder, schizophrenia, shared psychotic disorder, major depressive disorder, and bipolar disorder. They are also the major feature of delusional disorder. Individuals with delusional disorder suffer from long-term, complex delusions that fall into one of six categories: persecutory, grandiose, jealousy, erotomanic, somatic, or mixed.

Comparison chart

Delusion versus Hallucination comparison chart
Edit this comparison chartDelusionHallucination
Definition A delusion is commonly defined as a fixed false belief and is used in everyday language to describe a belief that is either false, fanciful or derived from deception. In psychiatry, the definition is implies that the belief is pathological. A hallucination is a perception in the absence of a stimulus. It's a perception a noise, smell, or sight, in a conscious and awake state, in the absence of external stimuli that has qualities of real perception.

Different types

Delusions are erroneous beliefs and hallucinations are perceptions of stimuli that don't actually exist. For example, a delusion may be a belief that the government is controlled by reptilian men who are poisoning the water supply to enslave the masses. A hallucination may be hearing "voices" or seeing ghosts.

It is common for many people to hold a shared delusion that stems from their paranoia or belief system. People in cults may all believe that their leader is a messiah or that the end of the world is nigh. In fact, some atheists believe that all organized religion and faith in God is a delusion. In contrast, it is quite rare for two people to share a hallucination.

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Delusions may be present in any of the following mental disorders:



In many cases, chronic hallucinations caused by schizophrenia or some other mental illness can be controlled by medication. If hallucinations persist, psychosocial therapy can be helpful in teaching the patient the coping skills to deal with them. Hallucinations due to sleep deprivation or extreme stress generally stop after the cause is removed.


Delusional disorder is typically a chronic condition, but with appropriate treatment, a remission of delusional symptoms occurs in up to 50% of patients. However, because of their strong belief in the reality of their delusions and a lack of insight into their condition, individuals with this disorder may never seek treatment, or may be resistant to exploring their condition in psychotherapy.

Work up and diagnosis



The examiner bases the diagnosis of delusion on the following criteria set forth in the Diagnostic and Statistical manual of Mental Disorders, 4th edition-text revision:


Of hallucinations

Treat hallucinations symptomatically with antipsychotic drugs (e.g., haloperidol, risperidone, olanzapine)

Of delusions


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