Schizophrenia

What percentage of the global population suffer from schizophrenia?

1%

Do more males or females suffer from schizophrenia?

More males from Sz

Is Sz more likely to affect people living in the countryside or the city?

More likely to affect people in the city

Is Sz more likely to affect working class or middle class people?

Working class people

How is SZ classified?

Through APA's DSM-5 or the WHO International Classification of Diseases

How does the DSM-5 diagnose Sz?

- symptoms must be present for at least 6 months

- presence of at least one positive symptom for diagnosis

- subtypes removed

How does the WHO's ICD-11 diagnose Sz?

- symptoms must be present for at least one month

- presence of 2 or more negative symptoms is adequate for diagnosis

- 5 subtypes recognised

What are the two types of symptoms of Sz?

positive and negative

What are positive symptoms?

behaviors that are added to normal behavior

What are negative symptoms?

absence of normal or desired behavior

Name 3 positive symptoms of Sz

- hallucinations

- delusions

- disordered thinking

What are hallucinations?

Sensory experiences that have no basis in reality or distortions of stimuli that are genuinely there

What are the 4 types of hallucinations?

- tactile

- visual

- olfactory

- auditory

What are delusions?

Irrational beliefs that have no basis in reality

What are the 3 types of delusions?

- delusions of persecution

- delusion of control

- delusion of grandeur

What are the 2 negative symptoms of Sz?

- avolition

- speech poverty

What is avolition?

lack of purposeful, willed behaviour

Sufferers have reduced motivation to carry out activities

What is speech poverty?

Reduction in the amount and quality of speech

What are the 3 types of speech poverty?

- alogia

- echolalia

- affective flattening

What is alogia?

Speech seems blocked

What is echolalia?

Repeats other's words or phrases

What is affective flattening?

reduction in range and intensity of emotional expression

How does poor reliability act as a weakness of diagnosis of schizophrenia?

- Cheniaux et al had 2 psychiatrists independently diagnose 100 people using both DSM and ICD criteria

- inter rater reliability was poor, with one psychiatrist diagnosing 26 individuals according to DSM and 44 according to ICD

- other psychiatrist diagnosed 13 according to DSM and 24 according to ICD

- this poor reliability is a weakness of diagnosis of Sz

What is inter-rater reliability in the context of diagnosis?

inter-rater reliability in the context of diagnosis means the extent to which two or more mental health professionals arrive at the same diagnosis for the same individuals

How does poor validity weaken diagnosis of Sz?

- validity is the extent to which we are measuring what we are intending to measure

- one standard way to assess validity of diagnosis is criterion validity

- Cheniaux et al suggests that we are much more likely to be diagnosed using ICD than DSM

- this suggests that schizophrenia is either over-diagnosed in ICD or under-diagnosed in DSM

- either way, this is poor validity

What is criterion validity?

Do different assessment systems arrive at the same diagnosis for the same patient

How does co-morbidity weaken diagnosis of Sz?

- if conditions occur together a lot of the time then this calls into question the validity of their diagnosis and classification because they might actually be a single condition

- Sz is commonly diagnosed with other conditions

- Buckley et al concluded that around half of people with Sz diagnosis also have depression (50%) or substance abuse (47%)

- PTSD also occurred in 29% of cases and OCD in 23%

How does symptom overlap weaken diagnosis of schizophrenia?

- both schizophrenia and bipolar disorder involve positive symptoms like delusions and negative symptoms like avolition

- this questions the validity of both the classification and diagnosis of schizophrenia

- under ICD a person might be diagnoses with Sz, however, many of the same individuals would receive a diagnosis of bipolar disorder according to DSM criteria

- this is unsurprising given the overlap of symptoms, it even suggests that Sz and bipolar disorder may not be two different conditions but one

How does gender bias weaken diagnosis of schizophrenia?

- there is an issue of gender bias in the diagnosis where more men are diagnosed than women

- men are more likely to be diagnosed with Sz compared to women with a ratio of 1.4:1

- Cotton et al (2009) suggests this is because women have closer relationships and have greater support

- this strong interpersonal functioning could mask the fact they have Sz or the severity, this questions the validity as procedure for diagnosis only works well for one gender

How does cultural bias weaken diagnosis of schizophrenia?

- differing cultural norms may lead to the mislabelling of Sz by western doctors purely because they don't fit with western norms

- Pinto and Jones found british people of Afro-Caribbean origin are 9 times more likely to be diagnosed Sz than white British people. Yet this is not true of those in Afro-Caribbean countries

- this misleads people to think Afro-Caribbeans are genetically more likely to have Sz when this is simply not true

- less likely due to genetic vulnerability - more to be cultural bias