Organic Delusional Disorder:
Organic Delusional Disorder is a mental disorder that affects a person’s ability to tell the difference between reality and fantasy. It can manifest itself as unwavering beliefs in things that are not true. From a fear of constantly being followed to falling in love with strangers, there are many different ways that organic delusional disorder can affect people. 
It is a disorder in which persistent or recurrent delusions dominate the clinical picture. The delusions may be accompanied by hallucinations. Some features suggestive of schizophrenia, such as bizarre hallucinations or thought disorder, may be present. 
Organic delusional disorder affects people differently, but it generally revolves around very strong and unwavering beliefs in something (typically unreal or false.) It also results in a person’s inability to tell the difference between what is real and imagined. Some people may think they are king of the world, while others might insist the sky is yellow. There is a wide range of specific delusions that may shown by a person. 
According to ICD-10 (F06.2), presence of predominant delusions cause by an underlying organic cause is required for the diagnosis of organic delusional disorder, in addition to the general guidelines for the diagnosis of other organic mental disorders, described earlier.
It is important to rule out any major disturbance of consciousness, orientation, memory, or mood. The delusions are variable. The most common delusions are persecutory in nature. Hallucinations (visual more often than auditory) may accompany the delusions.
Schneiderian ﬁrst rank symptoms (SFRS) are usually not see the organic delusional disorder (in contrast to schizophrenia). 
The symptoms of delusional disorder include:
- Persistent delusions (in general they last more than one month).
- Delusions that contain exaggerated psychotic themes (from extreme jealousy to pangs of love for strangers).
- Unlike schizophrenia, which shares some of the symptoms of organic delusional disorder, there are no hallucinations associated with this mental disorder.
- Intense love for someone that is not known well.
- A constant fear of being poisoned.
- Even in cases where there is some truth to the fear or belief, there is usually an extreme exaggeration of circumstances. All of the symptoms stem from a physiological problem with the brain.
Generally, the symptoms are manageable enough for people to be able to lead normal, active lives. That said, guided therapy can still be helpful for people dealing with the symptoms of delusional disorder. 
- Drugs: Amphetamines, hallucinogens, cannabis, disulﬁram.
- Complex partial seizures (e.g. temporal lobe epilepsy).
- Huntington’s chorea (initial stages), Parkinson’s disease, Wilson’s disease, and idiopathic basal ganglia calciﬁcation.
- Right parietal lobe lesions, especially vascular lesions.
- Lesions involving limbic system (e.g. tumours).
- Spinocerebellar degeneration.
- Cerebral malaria.
- Herpes simplex encephalitis.
- Nutritional deﬁciencies (Vitamin B12, iron).
- Demyelinating disorders (such as multiple sclerosis, metachromatic leukodystrophy). 
It involve beliefs that someone (even someone you don’t know) is in love with you.
They are those where you have an inflated sense of worth, even if it is just being “connected” or “friends with” famous people.
They revolve around the insistence that your significant other is being unfaithful even if there is proof this isn’t the case.
They revolve around a feeling that you are being singled out for mistreatment.
They concern the belief that you have a physical defect or serious medical problem.
They are those that have characteristic of more than one of the above types of delusional disorders, with none of them being predominate.
They are those not cover by the above descriptions of delusional disorders. 
Organic delusional disorder secondary to amphetamine use may difﬁcult to differentiate from paranoid schizophrenia.
The differentiating points are:
- An acute onset.
- History of amphetamine use prior to the onset.
- Predominant visual hallucinations which may be ﬂeeting.
- Absence of formal thought disorder and a more ‘appropriate’ affect. 
- Treatment of the underlying cause such as removal of toxic agent in amphetamine psychosis.
- Symptomatic management with a low dose of an antipsychotic medication (such as Risperidone, Haloperidol, Olanzapine, or Quetiapine) may needed.