The main feature is the presence of psychotic symptoms- i.e. hallucinations/delusions. These are different from mood disorders in that they are qualitatively different from normal rather than quantitively different.
The symptoms of psychosis can also be split into two main groups:
- Positive symptoms– an excess or distortion of ‘normal’
In schizophrenia, these are commonly persecutory, thought interference or passivity delusions.
In SZD, these are commonly auditory 3rd person narrative, thought echo/discussion and/or persecutory
Formal though disorder
A loss of the normal flow of thinking as shown through writing/speech. Commonly a feature associated with thought broadcasting, thought insertion, thought withdrawal etc.
- Negative symptoms– decrease or loss of normal function
Loss of motivation/spontaneous behaviour; flattened mood, blunting of affect and anhedonia; poverty of thought/speech.
Belief that external events are related to oneself. They can vary in intensity from a brief thought to frequent and intrusive thoughts to delusional intensity (self-referential delusions or delusions of reference). E.g. others are speaking/laughing about me; the tv/radio are transmitting informatioin for me; the car registration contains coded messages for me.
In psychosis, there is a general lack of insight– i.e. the patient does not recognise that this is abnormal.
Schneider’s First Rank Symptoms of SZD
- Auditory hallucinations- 3rd person- arguing/discussing, running commentary or thought echo
- Passivity phenomenon– may have thought alienation (insertion/withdrawal/broadcasting)
- Delusional perception- a fully formed delusion which arises from a real/genuine perception
- e.g. the door closed so the FBI must be holding me here
NB must be in the absence of organic impairment or psychoactive drug use and must last >1 month (otherwise a psychotic episode). The presence of one or more of these symptoms is positive evidence for a diagnosis of SZD (BUT 20% of mania will present with one too).