Brief Answer:
When psychosis is due to an organic disease.

Detailed Answer:
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Psychosis is a psychiatric term used to describe an abnormal condition of the mind in which there is extreme impairment of ability to think clearly,to evaluate reality objectively.
It is a serious mental disorder that can cause delusions, hallucinations, serious defects in judgment and other cognitive processes.

Psychoses are classified as organic or functional mental disorders.

Organic psychosis is when the psychotic symptoms (delusions,hallucinations etc) are caused by a known physical cause in the brain (organic disease of the brain). In this case psychosis symptoms are considered secondary due to a disturbance in brain structure or function.
Many medical conditions can affect brain function and cause symptoms of hallucinations and delusions including :-Head injury ,brain tumor ,Alzheimer disease, cerebral arteriosclerosis, thyroid disease, vitamin deficiencies, liver disease, epilepsy, Parkinson disease, and encephalitis,etc.


Hope I answered your query.
If you have any other question or doubt to clarify,please feel free to ask,I will be happy to help.

Take care.
Dr.Rovena Murati

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