A delusion is a fixed, false personal belief held

with absolute conviction despite all evidence

to the contrary. The belief is outside the

person’s normal culture or subculture and

dominates their viewpoint and behavior.

Delusions may be described in terms of their

content (e.g. delusions of persecution or

grandeur). They can be mood congruent (the

content of delusion is appropriate to the mood

of the patient), or mood incongruent.

Delusions are described as systematized if they

are united by a single theme.

A primary delusion arises fully formed

without any discernible connection with

previous events (also called autochthonous

delusions), e.g. “I woke up and knew that my

daughter was the spawn of Satan and should

die so that my son could be the new Messiah”.

Secondary delusions can be understood in

terms of other psychopathology, for example

hallucinations: “The neighbors must have

connected all the telephones in the building;

that’s why I can hear them all the time”.

The term delusional mood is slightly

confusing in that it does not describe an

abnormal belief, but refers to an ill-defined

feeling that something strange and threatening

is happening which may manifest as perplexity,

uncertainty or anxiety. This may precede a

primary delusion or a delusional perception,

which involves a real perception occurring

almost simultaneously with a delusional

misinterpretation of that perception, e.g. “I saw

the traffic lights change from red to green and

knew that I was the rightful heir to the throne of

England”.

Overvalued ideas are unreasonable and

sustained intense preoccupations maintained

with a strong emotional investment but less

than delusional intensity. The idea or belief

held is demonstrably false and not usually held

by persons from the same subculture.

Delusions may be classified in terms of their

content, for example delusions of...

Persecution An outside person or force is in

some way interfering with the sufferer’s life or

wishes them harm, e.g. “The people upstairs

are watching me by using satellites and have

poisoned my food”.

Reference The behavior of others, objects, or

broadcasts on the television and radio have a

special meaning or refer directly to the person,

e.g. “A parcel came from Sun Alliance and the

radio said that ‘the son of man is here’, on a

Sunday, so I am the son of God”.

Control The sensation of being the passive

recipient of some controlling or interfering

agent that is alien and external. This agent can

control thoughts, feeling and actions (passivity

experiences), e.g. “I feel as if my face is being

pulled upwards and something is making me

laugh when I’m sad”.

Grandeur Exaggerated belief of one’s own

power or importance, e.g. “I can lift mountains

by moving my hands, I could destroy you!”.

Nihilism Others, oneself, or the world does not

exist or is about to cease to exist (often called

Cotard’s syndrome), e.g. “The inside of my

tummy has rotted away. I have no bowels”.

Infidelity One’s partner is being unfaithful

(also known as delusional jealousy or the

Othello syndrome).

Doubles A person known to the patient, most

frequently their spouse, has been replaced by

another (also known as Capgras’ syndrome or,

confusingly, ‘illusion’ of doubles).

Infatuation A particular person is in love with

the patient (also known as erotomania or de

Clerambault’s syndrome).

Somatic Delusional belief pertaining to part of

the person’s body, e.g. “My arms look like

they’ve been melted and squashed into a

mess”.