Classification and diagnosis of schizophrenia

Schizophrenia is characterized by a profound disruption of cognition and emotion which affects a persons language, thought, perception, affect and sense of smell

Diagnostic criteria DSM-IV-TR - duration - least a months duration of two or more positive symptoms - delusions - bizarre beliefs that seem real to the person with schiz but aren't real, they can be paranoid or may involve inflated beliefs about the persons power and importance - hallucinations are bizarre, unreal perceptions of the environment that are usually auditory but can be visual or tactile - possibility of a mood disorder or organic must be excluded   

Reliability - the extent to which different psychiatrists can agree on the same on diagnosis when assessing patients - existence of classification systems such as the DSM is claimed to lead to a much greater agreement in the diagnosis of schizophrenia - different classification systems used for diagnosis - in the US the DSM is used and in the UK the ICD is also used - issue with this is that they describe schizophrenia in different ways which creates problems in assessing reliability

Unreliable diagnosis - Rosenhan demonstrated unreliability of diagnosis by arranging for pseudopatients to present themselves to psychiatric hospitals claiming to be hearing voices - all were diagnosed with schiz and admitted despite the fact they displayed no further symptoms during their hospitalization - non of the staff recongnized they were normal 

Reliability of DSM is till not that high - Whaley - found an inter-rater reliability correlations in the diagnosis of schiz as low as +1.1

Cultural differences - Copeland - gave a description of a patient to US and UK psychiatrists  - of the US psychiatrists 69% were diagnosed with schiz whereas only 2% were diagnosed in the UK with the same diagnosis - Blake found psychiatrists are 6 times more likley to diagnose schiz if the description refers to a patient as black African American compared to a white patient with the same symptoms

If deulsions are bizarre this is sufficient diagnosis for schiz - Mojtabi and Nicholson found when 50 senor psychiatrists were asked to distinguish between bizarre and non bizarre delusions - inter-rater realiability of only +4.0 - lacks sufficient reliability for accurate diagnosis

implications for Rosenhan study - situational factors + expectations may be more influential when making a diagnosis of schiz than are clinical characteristics - follow up study - rosenhan warned hospitals that he was sending out psuedopatients - resulted in a 21% detection rate even though non were actually sent

Comorbidity - Schneider referred to delusions, thought, broadcasting and auditory hallucinations as first rank symptoms  - could be used to distinguish schizo from other psychotic disorders - Allardyce - claims symptoms used to classify schiz dont define a specific disorder - its symptoms are found in other categories of psychosis

Predictive validity - if a disorder has a high predicitive vailidity then it should be clear how the disorder would develop and how people would respond to treatment - schizo has low predicitve validity

first rank symptoms dont make diagnosis more accurate - Bentall claim that many of the first rank symptoms of schiz are also found in other disorders such as bipolar - making it difficult to separate schiz as a distinct disorder 

overlap with other disorders- Torrey - overlap of bipolar with schiz in terms of risk factors and neural abnormalitiies - possible that these 2 disorders may form a spectrum of psychosis rather than discrete conditions

Little evidence that outcomes are the same - the prognosis for people with schiz varies at about 20% recovering their previous level of functioning - 10% showing significant improvement and 30% some imporvement whilst 40% never really recover - demonstrates little predicitve validity for a diagnosis of schiz with so much variation in the prognosis of the disorder