Lesson 4: Biological explanation for schizophrenia – Genetics: Flashcards
What are genetic schizophrenia
Genetic causes of schizophrenia: AO1:
The mental disorder schizophrenia is inherited through generations and transmission of genes and DNA. Schizophrenia runs in families/familial link and involves a combination genes (polygenic)
The gene NRG1 contributes to the genetics of schizophrenia.
NRG1 participates in glutamatergic signalling. It regulates the (NMDA) receptor which is a glutamate receptor (primary excitatory neurotransmitter in the brain).
NRG3 is another schizophrenia susceptibility gene
Explain study by Ripke
• Ripke suggested that schizophrenia might be polygenic, whereby a number of candidate genes might be responsible for schizophrenia
• He did a meta-analysis of studies that looked at candidate genes and schizophrenia sufferers.
• 37,000 schizophrenia sufferers were investigated compared to 11,000 controls
• He found that 108 separate genetic variations were associated with increased risk of getting schizophrenia.
• These genes seemed to code for the functioning of the neurotransmitter dopamine.
• High levels of dopamine can cause schizophrenia
Evaluation of ripke study
An Evaluation of the study by Ripke: (AO3):
1) A disadvantage of genetics is that we must be cautious when looking at genetics alone as a cause for schizophrenia. Other approaches need to be examined in terms of what could cause schizophrenia, for instance the behavioural model might suggest that children can learn abnormal behaviours via the environment (classical and operant conditioning and social learning theory), and therefore this could help develop schizophrenia rather than genetics. (-)
2) A problem with genetics is that is does not offer a full explanation as to how schizophrenia is transmitted. Just because someone has the gene for schizophrenia, it does not automatically mean that they will get the illness (due to the gene possibly being recessive). The diathesis stress model would advocate the idea that a person is more likely to get schizophrenia if they have the gene for the illness, and then a factor in the environment will trigger the illness (for example stress). Therefore the diathesis stress model highlights the importance of genetics, but also includes an environmental factor that helps trigger the illness (-)
3) There is a great amount of research support from many psychologists that schizophrenia does seem to be caused by genetics. There is evidence from Gottesman and Kety which makes the evidence robust and strong. Therefore genetics cannot be ignored as a major cause for schizophrenia (+)
4) To contradict the research conducted by Ripke, sometimes schizophrenia can occur in the absence of genetics or family history. There could be a mutation in parental DNA that causes schizophrenia in their future offspring, (such as a sperm cell might be damaged by radiation, poison or a viral infection). There is also a positive correlation between the paternal age of fathers and the risks of having a schizophrenic child. 0.7% if the father is under the age of 25, which increases to 2% if the father is over the age of 50. (-)
5) The research conducted by Ripke can by supported by the dopamine hypothesis which states that high levels of dopamine in the D1 and D2 receptors in the brain can cause schizophrenia. Ripke’s work can be praised for linking together two biological mechanisms that could cause schizophrenia: genetics and the link to high dopamine production. (+)
Explain Gottesman and shields study on twins and schizophrenia
• Gottesman and Shields investigated 224 sets of twins from 1948-1993 who appeared on the Maudsley twin register (106 sets of twins were MZ and 118 were DZ).
• 120 males and 104 females were studied
• The average sample age was 46 years and they came from a range of ethnic backgrounds.
• Conducted in a London hospital and was a longitudinal study over a period of 25 years.
• The study relied on the fact that one twin already had the illness of schizophrenia, and concordance rates were investigated (which examined the likelihood or the chances of the healthy twin becoming schizophrenic over time)
• The methods that Gottesman and Shields used to diagnose schizophrenia included the following:
a) In depth interviews
b) Doctors case notes
c) The DSM
The result found that:
• 48% of MZ twins were both concordant for schizophrenia by the end of the study
• 17% of DZ twins were both concordant for schizophrenia by the end of the study
• This indicates that schizophrenia does have a genetic basis to some extent, especially for MZ twins.
• For DZ twins, genetics seems less prominent as a cause for schizophrenia (but the risk is still greater than for the general population which is 1%)
Evaluation of gottesman and shields study
1) A strength of Gottesman and Shields study is that it was longitudinal. This means that the schizophrenic patients could be tracked over long periods of time in order to monitor the development of the illness schizophrenia. (+)
2) The research by Gottesman and Shields ignores the behavioural approach when examining the causes of schizophrenia. Identical twins often copy and model (social learning theory) each other’s behaviour, so it could be that the healthy twin has modelled or copied schizophrenic behaviour rather than getting the illness via genetics. (-)
3) The research by Gottesman and Shields has the advantage of being both reliable and valid when investigating the genetic cause for schizophrenia. The research diagnosed schizophrenia using in depth interviews, doctor case notes and the DSM. Therefore there were three different methods that were used to diagnose the illness which means that there would have been more chance of inter-rater reliability and higher validity (+)
4) The research conducted by Gottesman and Shields could be criticised because it relied on interviews with patients. Schizophrenia patients often have difficulty with their speech and communication and therefore some patients might have found it difficult to communicate their symptoms effectively to the psychologists/psychiatrists. Therefore this issue could have had a negative effect on the diagnosis and classification of schizophrenia. (
Explain Adoption study by Kety
• Prospective longitudinal study carried out in Denmark and began in 1972. Follow up studies occurred in 1974 and 1989
• 207 adopted children studied, their biological mothers had been diagnosed with schizophrenia (high risk group).
• Matched control group of 104 adopted children who had healthy biological mothers (who did not have schizophrenia), they were labelled low risk group
• Children aged 10-18 at the start of the study and both groups matched in terms of age, gender, parental socio-economic status.
• Results showed there was a strong genetic basis for mental disorders (not just schizophrenia)
• 16.2% of the high risk group were diagnosed with schizophrenia, compared to 1.9% from the low risk group
• Schizotypal personality disorder was diagnosed in 18.8% of the high risk group and 5% in the low risk group (this is characterised by milder schizophrenia symptoms and the patient does not lose complete contact with reality).
• The high risk group had a total of 35% that experienced a mental disorder, compared to 6.9% of the low risk group.
Kety study Evaluation study
1) Supporting the research by Kety is a study conducted by Erlenmeyer-Kimling (1997) known as the, “New York High Risk Project.” This study was a longitudinal piece of research that lasted 25 years and found similar results to Kety. This further supports the idea that biological causes (genetics) are a strong factor that can cause schizophrenia. (+)
2) Kety conducted a prospective longitudinal study which has many advantages. This method looks at children before they show any signs or symptoms of schizophrenia and does not rely on retrospective data (whereby the patient already has schizophrenia and would need to remember when they got the symptoms, which could be quite unreliable). Kety was able to follow the participants accurately (+)
3) An advantage of Kety’s research is that all of the children in the study were carefully matched on relevant variables such as age, gender and socio economic status. This makes the study very fair and controlled and also helps to eliminate confounding variables that could effect the diagnosis of schizophrenia (+)
4) One problem with the study conducted by Kety is that we cannot separate genes from the environment. The children who were born to schizophrenic mothers still would have shared the same environment as their mothers for a short time before being adopted. Therefore it is very hard to separate the genetics element from the environment completely and this needs to be carefully considered when interpreting the results (-)
5) The reliability of diagnosing schizophrenia in this study can be problematic. The mothers had been diagnosed with schizophrenia before the introduction of diagnostic systems e.g. DSM. There have been criticisms from other psychologists that maybe the mothers did not have schizophrenia at all, but might have had a very similar illness called, “schizotypal personality disorder”. The symptoms of this illness include the person having discomfort in close relationships, cognitive distortions, eccentric behaviour, lacking humour, digressive speech and inappropriate emotions. (-)
