biological explanatioms for schizophrenia✅ Flashcards
what does Gottesman report in regards to inheritance as a genetic explanation for schizophrenia
- the chances of first-degree relatives developing the disorder is 12%
- if both parents have schizophrenia there is a 40% likelihood that their child will develop the disorder
what does Tsuang say in regards to inheritance as a genetic explanation for schizophrenia
estimated that a first degree relative of a schizophrenic has 5-20 times higher risk of developing the illness
describe a twin study regarding genetic explanations for schizophrenia
- gottesman analysed genetic component of schizophrenia
- found that concordance rate for schizophrenia is higher in MZ twins
describe adoption studies regarding genetic explanations for schizophrenia
- more effective as it isolated environmental factors to focus on genes
- Heston compared children of schizophrenic mothers who had been adopted during first month of life compared to children who had been raised in the same homes
- no kids from CG developed it but 17% of kids from schizophrenic mothers did
describe Candidate Genes regarding genetic explanations for schizophrenia
- Ripke studied genetic makeup of 37000 people and found 108 variations linked with schizophrenia —> polygenic
- different studies have identified different candidate genes so schizophrenia is aetiologically heterogeneous (may be caused by many different genes)
what are some overall A03 points of the genetic explanation of schizophrenia
- rearing patterns may explain family similarities
- difference in concordance rates between twins may be down to environment
- may be other explanations
- biologically deterministic
describe an A03 point of Genetic explanations regarding issues regarding family similarities
- the fact that schizophrenia appears to run in the family may be more to do with rearing patterns and have nothing to do with heredity
- EG: research in expressed emotion shows a negative emotional climate may lead to stress, triggering a schizo episode
describe an A03 point of Genetic explanations regarding difference in concordence rates being down to environment
- it’s assumed that greater rates in MZ twins are down to genetic similarity
- however Joseph found MZ twins are treated more similarly that DZ twins
- environments differences may differentiate the 2 type of twins
describe an A03 point of Genetic explanations regarding other explanations
- 2/3 of ppl with schizophrenia have no relative with the diagnosis
- however one explanation is a mutation from parental DNA
eg: paternal sperm cells (can be caused by viral infection) - Malaspina found positive correlation between paternal age (risk of sperm mutation) and risk of schizophrenia
- therefore may be other explanations
describe the neural correlates explanation of schizophrenia
- believes schizophrenia has developed due to structural and functional brain abnormalities
- caused by enlarged ventricles
what did Jonstone find regarding neural correlates as an explanation of schizophrenia
- schizophrenics had enlarged ventricles –> suggests schizo is related to loss of brain tissue
what did Andreasen find regarding neural correlates as an explanation of schizophrenia
- conducted controlled CAT scan study sn found significant enlargement of ventricles in schizos
- HOWEVER this was only the case for men
what does the Dopamine hypothesis claim
- claims that an excess of the neurotransmitter dopamine in certain regions of the brain is associated with positive symptoms of schizophrenia
describe what happens leading to hallucinations according to the dopamine hypothesis
- msgs from neurons that transmit dopamine fire too easily or too often
- this leads to hallucinations or delusions
what is the link between schizophrenia and D2 receptors according to the dopamine hypothesis
- schizos are thought to have high levels of D2 receptors on receiving neurons
- results in more dopamine binding and therefore more neurons firing
how have dopamine agonists such as amphetamines illustrate the dopamine hypothesis
- amphetamine is a dopamine agonist –> stimulates nerve cells containing dopamine, causing the synapse to flood with this NTM
- ppl who are exposed to large doses of a dopamine-releasing drug can develop symptoms of schizo
describe the Revised Dopamine Hypothesis in regards to neural correlates
- Davis and KAhn said positive symptoms are caused by excess of dopamine in subcortial areas of brain, particularly is mesolimbic pathway
-however, negative and cognitive symptoms are though to arise from a deficit of dopamine in the pre frontal cortex (mesocortical pathway)
describe how neural imagine was used to illustrate the Revised Dopamine Hypothesis
- Patel et al. used PET scans to asses dopamine levels in schizos vs. normal ppl
- found lower levels of dopamine in the dorsolateral prefrontal cortex of schizos
what did Wang and Deutch find using animal studies regarding the Reviced dopamine hypothesis
- induced dopamine depletion in pre-frontal cortex of rats
- resulted in cognitive impairment (eg memory loss)
- researcher were able to reverse it using olanzapine
what are some overall A03 points of the biological explanation for schizophrenia
- evidence to support –> Leucht
- opposing evidence –> dopamine hypothesis is far from conclusive
- other explanations
describe an A03 point of the biological explanation regarding evidence to support
- Leucht carried out meta analysis to study effectiveness of different antipsychotic drugs compared with placebo
- found all drugs tested to be effective in treatment of positive and negative symptoms
- normalisation of dopamine leading to reduction of symptoms supports dopamine hypothesis’ belief that excess of dopamine may be causing these symptoms
describe an A03 point of the biological explanation regarding opposing evidence
- Moncrieff states although stimulant drugs such as amphetamine have been shown to induce schizophrenic episodes, such stimulants may affect other NTMs
- also, confounding variables such as stress and smoking haven’t been considered
- the idea that schizo symptoms are caused by overactivity of dopaminergic system isn’t supported
what is the prime treatment for schizophrenia
antipsychotic drugs
describe antipsychotics as a drug therapy for schizophrenia
- dampen symptoms so a degree of normal can occur
- may be required in the short or long term
- divided into typical (traditional) and atypical (newer) drugs
