Schizophrenia: diagnostic criteria

Psychology A2 · Clinical Psychology. The idea in plain words, the rules to remember, the mistake to avoid and a worked example, written and checked by Mega Lecture.

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The idea

Schizophrenia is a psychotic disorder: the person loses touch with reality in some ways. ICD-11 sorts the symptoms into positive symptoms, which are added to normal experience (delusions, hallucinations, disorganised thinking), and negative symptoms, which are losses of normal functioning (flat emotion, little speech, no motivation).

A delusion is a fixed false belief. Freeman et al. (2003) studied persecutory thoughts safely by putting non-clinical volunteers into a virtual reality library with computer characters that behaved neutrally. Some people still judged the characters as hostile, and these people tended to be more anxious and more sensitive to others. This suggests persecutory thinking lies on a continuum in the general population.

Rules to remember

ICD-11 diagnosis: at least two symptoms, at least one of them a core symptom, present most of the time for one month or more.
Core symptoms: persistent delusions, persistent hallucinations, disorganised thinking, experiences of influence, passivity or control.
Negative symptoms: blunted affect, poverty of speech (alogia), lack of motivation (avolition), social withdrawal.
ICD-11 has no subtypes such as paranoid or hebephrenic; symptom dimensions are rated instead.
Types of delusion: persecutory (others mean to harm me), grandiose (I have special power or importance), reference (neutral events carry a message for me), control (an outside force directs me).
Freeman et al. (2003): the avatars were neutral, so any hostile reading came from the participant, not from the scene.
A case study of one patient is idiographic: rich detail, but hard to generalise.

Common mistake

Students think 'positive' means good and 'negative' means bad. Positive means something is added to normal experience; negative means something is taken away.

Worked example

Omar believes that his neighbours have placed cameras in his flat because they plan to poison him. There are no cameras. Which type of delusion is this, and is it a positive or a negative symptom?

The belief is false and firmly held, so it is a delusion.
Its content is that other people intend to harm him, which is the persecutory type (not grandiose, reference or control).
A delusion is an experience added to normal thinking, so it is a positive symptom.

Answer: A persecutory delusion, which is a positive symptom.

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