Schizophrenia Flashcards
What two main classification systems are in use for diagnosing schizophrenia
DSM-5
ICD-11
what do they require for a diagnosis
DSM-5 = one positive symptom
ICD-11 = two or more negative symptoms
what is schizophrenia
a severe mental illness where contact with reality and insight are impaired, an example of psychosis
What are positive symptoms
additional experiences beyond ordinary
examples of positive symptoms
Hallucinations = unreal perceptions of the environment, sensory experiences e.g hearing voices or seeing people
Delusions = irrational beliefs that seem real to the person e.g believing they are Jesus
Disorganised speech = result of abnormal thought processes where individual has problem organising thoughts or speech
Grossly disorganised or catatonic behaviour = lack of motivation to start or complete a task, leads to difficulties in daily living and can decrease personal hygenie
What is a negative symptom?
reduction or loss of normal functions
they reduce ability to manage everyday activites
Examples of negative symptoms
speech poverty = reduction in fluency and quality
Avolition = reduction of intrests and desires and inability to start tasks
Affective flattening = reduction in the range of intensity of emotional expression e.g facial expression
Anhedonia = loss of interest or pleasure in almost all activities
What is diagnostic reliability?
Clinicans must be able to reach the same conclusions at two different points in time (test-retest reliability) or
different clincians must reach the same conclusions (inter-rater reliability)
evidence of diagnostic reliability
Osorio et al reported excellent relibaility for DSM-5 schizophrenia reliability
inter-rater reliability +0.97
test-retest reliability +0.92
AO3 - lack of inter-rater reliability
Research suggests significant variation between countries when it came to diagnosing
Copeland gave US and British psychologists description of a paitent
60% US compared to 2% British gave the same diagnosis
AO3 - unreliable symptoms
for diagnosis only one of the symptoms is required if ‘delusions are bizzare’
50 psychatrists were asked to differentiate between ‘biazzare’ and ‘non biazzare’ delusions, produced inter-rater reliablity correlations of only 0.40
suggests central diagnostic requirement lacks sufficient reliability = cannot be an accurate method
Why does diagnosis of schizophrenia have low validity
- gender bias
- symptom overlap
- co-morbidity
- criteria validity
Gender bias in diagnosing schizophrenia
occurs when accuracy of diagnosis is dependent on gender of individual
men are diagnosed with schizophrenia more often than women
diagnostic catogeries may be baised to pathologising one gender rather than the other
= some women miss out on treatmeant due to a lack of diagnosing
Symptom overlap and Co-morbidity/ AO3 for conseuquences of co-morbitidy
Many symptoms of S are also found in other disorders
most who are diagnosed with S have symptoms of other disorders which they could be diagnosed with it
meta-analysis found 12% of paitents w S also fulfilled the diagnostic critera for OCD and 25% displayed significant OCD symptoms
AO3 - validity of diagnostic manuals
Cheniaux et al (2009)
two psychatrists independently asses the same 100 clients
68 diagnosed with schizophrenia with ICD and 39 with DSM
means S is either over or under diagnosed depending on the criteria you use
suggests criterion validity is low
AO3 - research support for gender bias
Loring and Powell
Male and female psychatrists read two cases of paitents behaviour
If paitents described as male or no info about gender, 56% gave diagnosis
when female only 20%
this gender bias was not evident amoung femal psychatrists, suggesting diagnosis also influenced by gender of clincian
The dopamine hypothesis
- excess of dopamine in certain regions of the brain is associated with the positive symptoms of schizophrenia (hyperdopaminergia)
- ‘normal’ individuals exposed to large doses of dopamine relasing drugs develop the characteristic symptoms of a schizophrenic episode
- antipsychotic drugs block the activity of dopamine, eliminating symptoms such as hallucinations
The revised dopamine hypothesis
- Davis and Kahn proposed that positive symptoms are caused by excess of dopamine in subcorticol areas of the brain
- negative and cognitive symptoms caused by a deficit of dopamine in prefrontal cortex
AO3 - evidence supporting dopamine hypothesis
- successful treatment using drugs that change levels of dopamine in brain
- concluded that all the anti-psychotic drugs tested in their meta-analysis were significantly more effective than the placebo in treatement of + and - symptoms
AO3 - challenges to the dopamine hypothesis
- Noll claims strong evidence against the orginal and revised hypothesis
- antipsychotic drugs do not alleviate hallucinations and delusions in 1/3 of people
- in some people hallucinations and delusions present despite normal dopamine levels
- suggests that rather than dopamine being the sole cause, other neurotransmitters may also produce symptoms
Genetic factors - concordance
family studies
- show more common in biological relatives of a perosn with S
- closer degree of genetic relatedness, greater the risk
- Gottesman children with two S parents had concordance of 46%
twin studies
- Joesph pooled data and found concordance MZ 40.4% and DZ 7.4
adoption studies
- Tienari et al found of 164 adoptees whose bio mothers diagnosed with S, 11 also recieved a diagnosis compared to 4 control adoptees (born to non-S mothers)
Genetic factors - candidate genes
- S is polygenic - requires a number of factors to work in combination
- so many genes have been identifies
- Ripke et a carried out a genome-wide study and found 108 seperate genetic variations associated with increased risk
AO3 - MZ twins have similar environments
- assumption that MZ and DZ twins environments are equivalent, therefore assumes differences are down to genetic factors
- however MZ experience more similar environments and treated more similar
- suggests that differences in concordance rates between MZ and DZ reflect environmental differences as well as genetic
AO3 - strong evidence for genetic basis
- family studies show increased risk with genetic similarity
- Hilker et al found MZ 33% and DZ 7%
- adoption studies show that biological children with parents S are at greater risk even if they grow up in an adoptive family
- shows some people are more vulnerable to S because of genes
