A delusion is false, firm (unshakeable) belief that is not accepted by other members of patient’s culture and society. Above is an example of delusion of infidelity (morbid jealousy, Othello syndrome) i.e. False belief that one's lover has been unfaithful. Persecutory delusions (paranoid) : The patient feels that he is being persecuted against.There is a false belief that one is being harmed, threatened, cheated, poisoned, harassed or spied on or is a victim of a conspiracy to damage his reputation. The supposed persecutor of the patient may be people in the environment (e.g., members of the family, neighbours, former friend) or may be political or religious groups. These delusions occur in schizophrenia (especially paranoid), severe affective disorders (severe mania or severe depression) and organic brain syndrome. This is the most common type of delusion. The delusion of persecution may occur in the context of primary delusional experiences, auditory hallucinations, bodily hallucinations or experiences of passivityGrandiose delusion (expansive delusions) : False belief that one is exceptionally powerful, talented or important.These delusions are seen most commonly in mania, However, can also occur in schizophrenia and organic states.Delusions of reference : False belief that certain objects, people or events have intense personal significance and refer specifically to oneself,e.g., Believing that a television newsreader is talking directly about oneself, or people walking on the road are talking about him. These delusions are seen in schizophrenia, mania and organic states.Religious delusions : False belief pertaining to a religious theme, often grandiose in nature, e.g. : believing that one is a special messenger from God.These delusions are seen in schizophrenia.Delusions of love (erotomania) : False belief that another person is in love with one (commoner in a woman).In one form, termed de clerambault syndrome, a woman (usually) believes that a man, frequently older and of higher status, is in love with her.The delusion of infidelity (morbid jealousy, Othello syndrome) : False belief that one’s lover has been unfaithful. These are seen in schizophrenia, alcohol-related psychosis, organic states. The delusion of misidentification :Capgras syndrome (Delusion of double) : Belief that a familiar person has been replaced by an exact double i.e. an impostor. Fregoli syndrome : Belief that a complete stranger is actually a familiar person already known to one.The delusion of self - accusation or guilt : False feeling of remorse of guilt.It occurs in Depression.Nihilistic delusions : False belief that oneself, others or the world is non - existent or about to end.There are pessimistic ideas that the patient’s career is finished, he is about to die, the world is doomed.These occur in severe depression : If nihilistic delusions are accompanied by ideas concerning bodily function failure, e.g., putrefaction of intestines, etc. the syndrome is called COTARD’s SYNDROME. Hypochondriacal delusions :  False belief about one’s health, patient wrongly believes that he has a severe medical illness, contrary to the all medical evidence. It is seen in depression. The delusion of infestations : False belief that one is infested with small but visible organisms.As a monosymptomatic delusional disorder, this is called EKBOM SYNDROME. It is seen in the acute confusional state (due to drugs or alcohol withdrawal), in schizophrenia, in dementing illness, and as a delusional elaboration of tactile hallucinatory experiences (secondary to fornication).Delusion of control : Belief that his actions, impulses or thoughts are controlled by an outside agency and accordingly called as made action, made impulse or made an effect. Also called somatic passivity experiences (passivity phenomenon). Commonly seen in schizophrenia. Delusions concerning possession of thoughts : Patients with delusions about possession of thoughts may lose the conviction that their thoughts are their own. Most commonly seen in schizophrenia.