schizophrenia: biological explanation Flashcards
(15 cards)
explain the genetic basis of SZ
According to the genetic hypothesis, the more closely-related the family member to the person with
schizophrenia, the **greater their chance of developing the disorder. **
who studied the genetic basis os SZ
Gottesman
what did Gottesman find
someone with an aunt with schizophrenia has a 2% chance of developing it, compared to 48% if an identical twin has the disorder
explain candidate genes
Individual genes associated with the risk of inheritance
A number of individual genes each appear to confer a small increased risk of schizophrenia
> SZ is polygenic
what did Ripke et al find about genes involved with SZ
carried out meta-analysis > genetic make up of
37 000 patients was compared to that of 113 000 controls
108 separate genetic variations were
associated with increased risk of schizophrenia.
what did Benzel et al find about genes that may cause SZ
COMT , DRD4 , AKT1
have all been associated with excess dopamine in specific D2 receptors, leading to acute episodes, positive symptoms which include
delusions, hallucinations, strange attitudes
explain the original dopamine hypothesis
- Hyperdopaminergia in the subcortex
- schizophrenia patients suffered from an excessive amount of dopamine in the subcortex e.g. too many dopamine receptors in the Broca’s area
- high dopamine activity leads to acute episodes, **auditory hallucinations and speech poverty. **
explain the updated dopamine hypothesis
- Hypodopaminergia in the cortex
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Low levels of dopamine in the cortex
E.g. low levels in the pre-frontal cortex (responsible for thinking and decision making) - Associated with negative symptoms
What factors make people more sensitive to hyper/hypodominergia
Genetic vulnerability and early experiences of stress
what are neural correlates
Patterns of structure or activity in the brain that occur in conjunction with an experience and may be implicated in the origins of that experience
positive and negative symptoms both have neural correlates
explain neural correlates of positive symptoms
Allen et al: scanned the brains of patients experiencing auditory hallucinations and compared them to a control group whilst they identified pre-recorded speech as theirs or others.
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Lower activation levels in the superior temporal gyrus and anterior cingulate gyrus were
found in the hallucination group, who also made more errors than the control group. We can thus say that reduced activity in these two areas of the brain is a neural correlate of auditory hallucination
explain neural correlates of negative symptoms
Avolition involves the loss of motivation
* Motivation involves the** anticipation of a reward** and certain regions of the brain, for example, the ventral striatum, are believed to be particularly involved in this anticipation.
* Abnormality in the ventral striatum may be involved in the development of avolition.
Juckel et al found that activity in the ventral striatum is a neural correlate of negative symptoms of schizophrenia.
AO3: research to support dopamine hypothesis
Research shows that amphetamines increase DA and worsen symptoms in people with schizophrenia and induce symptoms in people without.
Additionally, antipsychotic drugs reduce DA activity and also reduce the intensity of symptoms
STRENGTH as it supports the idea that schizophrenia is due to abnormal dopamine functioning.
COUNTER: There is evidence to suggest that dopamine does not provide a complete explanation for schizophrenia. Ripke et al identified several neurotransmitters involved in schizophrenia such as glutamate. So **dopamine is not the sole cause of schizophrenia **
AO3: evidence to support genetic vulnerability
There is evidence for the genetic susceptibility
Gottesman found the more closely-related the family member to the person with schizophrenia, the greater their chance of developing the disorder.
Additionally, Tienari et al show that biological children of parents with schizophrenia are at heightened risk even if they grow up in an adoptive family.
STRENGTH as this shows that some people are more vulnerable to developing schizophrenia as a result of their genetic make up.
COUNTER: However research found that** 67% of people with schizophrenia reported at least one childhood trauma.** This suggests that genetic factors alone cannot provide a complete explanation for schizophrenia. This suggests that environmental factors also play a part.
