characteristics and diagnosis of schizophrenia - psychotic disorder

lifetime risk of schizophrenia in the general population

<1% (NHS)

torrey 2002 findings

abnormally high schizo rates in ireland + croatia, significantly lower rates in italy + spain

risk factors for schizophrenia

risk factors include low SES, minority ethnicity, urban residence

positive symptoms of schizophrenia

delusions (irrational beliefs), hallucinations (unusual sensory experiences)

negative symptoms of schizophrenia - loss of usual abilities and experiences

speech poverty/alogia (reduction in amount and quality of speech), avolition (difficult to engage in goal-directed activity, Andreasen 3 signs - poor hygeine + grooming, lack of persistence in work/school, lack of energy), affective flattening reduction in range and intensity of emotional expression

DSM-5 diagnosis of schizophrenia

continuous signs of disturbance for at least 6 months, including 1 month of active symptoms - 2 or more characteristics with at least 1 from delusions, hallucinations, alogia and avolition

ICD-10/11 diagnosis of schizophrenia

at least 2 symptoms must persist for at least one month, with at least one from delusions, hallucinations, disorganised thinking and loss of control over thoughts/actions

good reliabilty - strength of diagnosis

osorio - reported inter-rater reliability of +0.97 and test-retest reliability of +0.92 when using DSM-5 categories on 180 schizo patients, can be reasonably sure diagnosis of schizo can be applied

low validity - limitation of diagnosis

cheniaux et al - 2 psychiatrists independently assess same 100 clients - 68 diagnosed with ICD and 39 with DSM, schizo over or under diagnosed so criterion validity is low

comorbity (having 2 or more disorders at same time) of schizophrenia - limitation of diagnosis

buckley et al 50% of schizo patients have depression, symptom overlap hinders diagnosis as unsure if schizophrenic symptoms actually schizo or reflecting another disorder

gender bias - limitation of diagnosis

fischer and buchanan - men more diagnosed than women as ratio of 1.4:1, women underdiagnosed so may not receie treatment and services that benefit them, cotton - sexism in diagnosis, men more likely to get diagnosed than women, women mask symptoms and are less vulnerable than men, women have closer relationships to get support, androcentric diagnostic criteria

culture bias - limitation of diagnosis

pinto and jones - people of african-caribbean descent 9x more likely to be diagnosed but people living in afro-caribbean countries are not, ruling out genetic vulnerability, overinterpretation of symptoms in black british preople so discriminated against by a culturally biased diagnostic system but some symptoms have diff meaning in diff cultures e.g. Haitians see hearing voices as having communications with ancestors

symptom overlap (2 or more disorders share symptoms) of schizophrenia - limitation of diagnosis

swets - meta-analysis​ 12% of schizophrenia patients also fulfilled the diagnostic criteria for OCD, approx. 12% displayed significant OCD symptoms, schizo may not exist as distinct condition