schizophrenia Flashcards
what are positives symptoms
hallucinations
delusions
what are negative symptoms
avolition
speech poverty
what is avolition
lose of ability to perform basic actions
definition of reliability in term of diagnosis
If diagnosis is reliable then a diagnosis is consistent over time and by different psychiatrists. When two independent psychiatrists agree on a diagnosis of schizophrenia this is referred to as high inter-rater reliability. If a diagnostic system is to be valid, it must also have high reliability. Clearly if a disorder cannot be agreed upon (so low reliability) then all of the different views cannot be correct (so low validity).
definition of validity in term of diagnosis
One way to assess the validity of a diagnosis of schizophrenia is criterion validity. This refers to using two different measures which diagnose schizophrenia and seeing if they arrive at the same diagnosis.
in the UK the two diagnostic systems are ICD (International Classification of Diseases and Related Health Problems) and DSM (Diagnostic and Statistical Manual of Mental Disorders). Their criteria have some differences.
criterea for DSM-5 for schizophrenai
Two or more of the following for at least a one-month (or longer) period of time
* Delusions
* Hallucinations
* Disorganized speech
* Grossly disorganized or catatonic behaviour
* Negative symptoms, such as diminished emotional expression
* One of the positive symptoms – hallucinations, delusions or speech disorganisation must be present for a diagnosis
No subtypes in DSM 5 – although did exist in previous versions
criterea for ICD-10 for schizophrenai
Minimum of one very clear symptom (and usually two or more if less clear-cut)
Therefore, a key difference with the DSM and the ICD is that two negative symptoms are sufficient under ICD.
opposing evidence for validity/reliability
rosenhan
Pseudopatients presented to 12 different psychiatric institutions with single symptom of hearing a voice saying ‘hollow, empty, thud’. Once admitted they behaved normally. All but one of the patients were given the label of paranoid schizophrenia with the other patient being labelled as bipolar.
Rosenhan did a follow up study where he told the psychiatric institutions that he would send them more pseudopatients. **After three months they were confident that about a third of the new patients they were sent were pseudopatients, however none had been sent.
**
opposing evidence for validity/reliability
Cheniaux et al
Two psychiatrists independently diagnosed 100 patients using DSM and ICD. One psychiatrist diagnosed 26 with Schizophrenia according to DSM and 44 according to ICD.
The other diagnosed 13 using DSM and 24 according to ICD. Not only do the two diagnostic systems not agree but different psychiatrists interpret the criteria differently.
4 factors affecting reliability and validity
- comorbidity
- gender bias
- symptom overlap
- cultural bias
comorbidity
factors affecting reliability and validity
Schizophrenia is commonly diagnosed alongside other conditions. 50% of schizophrenic patients also have depression, 47% also have substance abuse, 29% have PTSD, 23% have OCD
symptom overlap
factors affecting reliability and validity
There is considerable overlap between symptoms of schizophrenia and other conditions.
For example, both SZ and bipolar disorder have symptoms of delusions and avolition.
Using the ICD a patient is more likely to be diagnosed with schizophrenia, but the same patient may be seen as bipolar using the DSM.
gender bias
factors affecting reliability and validity
Men are more likely to receive a diagnosis of SZ than women. This may simply be because men are more genetically vulnerable than women.
However,* before 1980 there was no gender difference* in rates of schizophrenia which suggests there could be gender bias in how schizophrenia is now diagnosed.
Women with schizophrenia tend to function better, more likely to work and maintain good family relations. This could lead to women being underdiagnosed.
cultural bias
factors affecting reliability and validity
People of Afro-Caribbean origin are significantly more likely to be diagnosed with schizophrenia.
However, rates of schizophrenia in Africa and the Caribbean are not any higher than in Europe, suggesting that this is not due to an increased genetic vulnerability.
There must be cultural bias in how schizophrenia is diagnosed.
Hearing voices is acceptable in African cultures because of cultural beliefs about communication with ancestors.
supporting evidence for schizophrenia being polygenic
Ripke et al (2014) carried out a meta-analysis of genome-wide studies (studies looking at the whole human genome and not focusing on particular genes) of schizophrenia. **The genetic makeup of 37,000 patients with schizophrenia was compared to that of 113,000 controls. **
They found that there were 108 separate genetic variations linked with increased risk of schizophrenia. These candidate genes associated with increased risk included those coding for the functioning of a number of neurotransmitters including dopamine.
evidence to support the gentic explanation
meta-analysis
**Gottesman **(1991) carried out a very large –scale family study. He pooled the data from 40 European studies published between 1920 and 1987. He conducted a meta-analysis of the genetic influences on schizophrenia. he recorded relationship to person with SZ and risk of developing SZ
1. identical twins - 48%
2. fraternal twins - 17%
3. children - 13%
evidence to support the gentic explanation
adoption
Tienari et al (2004) found that children of schizophrenia sufferers are still at a heightened risk of developing the disorder even if adopted into families with no history of schizophrenia.
However, schizophrenia can occur in people without a family history of the disorder +supporting evidence
opposing to genetic explanation
One explanation for this is mutation in their parent’s DNA, e.g. in the father’s sperm cells. This could be caused by radiation, poison or viral infection. This mutated DNA is then passed on to the child, leading them to develop schizophrenia later on.
This is supported by Brown et al (2002) who found a positive correlation between paternal age (associated with an increased risk of sperm mutation) and risk of schizophrenia, increasing from around **0.7% with fathers under 25 to over 2% in fathers over 50. **
what is dopamine
Dopamine is a neurotransmitter that helps control the brain’s reward and pleasure centres. It is excitatory in that it increases brain activity. Stimulant drugs such as caffeine, cocaine and amphetamines increase dopamine activity in the brain, increasing feelings of alertness.
Dopamine also helps regulate movement and emotional responses. It enables us not only to see rewards, but to take action to move toward them (motivation)
original dopamine hypothesis
was based on the discovery that** anti-psychotic drugs that were used to treat schizophrenia (by decreasing dopamine levels) **helped to reduce symptoms e.g., hallucinations and delusions. They also led to symptoms similar to Parkinson’s disease (associated with low levels of dopamine)
Evidence for this also comes from that fact that amphetamines increase the amounts of dopamine. Large doses of amphetamine given to people with no history of psychological disorders produce behaviour which is very similar to paranoid schizophrenia. Small doses given to those with Schizophrenia can worsen symptoms.
This led to a belief that Schizophrenia is related to high levels of dopamine (Hyperdopamingergia).
what is high levels of dopamine callled
Hyperdopamingergia
what is low levels of dopamine callled
hypodopaminergia
updated version of the dopamine hypothesis
- Abnormally high levels of dopamine (hyperdopaminergia) in the subcortex. Symptoms of speech poverty and auditory hallucinations can be explained by an excess of dopamine receptors in Broca’s area (responsible for speech)
- Abnormally low levels of dopamine (hypodopaminergia) in the prefrontal cortex. This is the area responsible for thinking and decision making). This is ***associated with avolition and lack of motivation.
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supporting evidence for hyperdopamingeria
Wise & Stein (1973) carried out **post mortems of schizophrenia patients and found abnormally low levels of Dopamine Beta Hydroxylase (DBH)** in the brain fluid. DBH is an enzyme whose function is to break down the neurotransmitter dopamine after release.
supporting evidence for hypodopamingeria
Meador-Woodruff et al (1997) carried out post-mortem investigation of 16 patients who had suffered from schizophrenia and compared them to 9 controls. They found **dramatic decreases in dopamine receptors in the prefrontal cortex. **
However, there is evidence to suggest that dopamine does not provide a complete explanation for schizophrenia.
genetic
Some of the genes identified in Ripke’s genome study code for the production of other neurotransmitters, so** although dopamine plays an important role so do other neurotransmitters**. Current research is focused in investigating the role of a neurotransmitter called glutamate.
cause and effect is not clear
genetic SZ
We can’t assume that imbalances in dopamine in the brains of people with schizophrenia are causing the disorder. It could be that the abnormal thinking caused by the disorder affect the biochemistry of the brain.
neural correlates
patterns of structure or activity in the brain that occur alongside an experience (in this case symptoms of schizophrenia). Negative and positive symptoms have different neural correlates.
examples of neural correlates of SZ
- an excess of dopamine recpetors in brocas may be responsible for speech disruption and auditory hallucinations
- low levels of dopamine in the frontal cortex [responsible for thinking/decision making] may be responsible for the negative symptoms of sz
research evidence to support the neural correlates of schizophrenia
x2
- **Juckel et al **(2006) measured activity levels in the **ventral striatum **in schizophrenic patients and found lower levels of activity in this area compared to a control group. They also observed a negative correlation between activity levels in the ventral striatum and the severity of overall negative symptoms. They concluded that activity in the ventral striatum is a neural correlate of negative symptoms of schizophrenia.
- Allen et al (2007) scanned the brains of patients experiencing auditory hallucinations and compared them to a control group. The scans were conducted whilst the subjects identified pre-recorded speech of theirs or others. Results showed that lower activation levels in the superior temporal gyrus and anterior cingulate gyrus were found in the hallucination group. They concluded that reduced activity in these two areas of the brain is a neural correlate of auditory hallucination.
correlation-causation problem
neural explantions of SZ
**Does the abnormal activity in a region of the brain CAUSE the symptom? Or do symptoms of SZ change the functioning of the brain? **For example there is a correlation between activity in the ventral striatum and negative symptoms. It could be that something wrong with the ventral striatum causes the symptoms. Or it could be that the *negative symptoms means that less information is processed by the ventral striatum, resulting in reduced activity. * Or there could be a third factor which influences both the ventral striatum and the negative symptoms.
