Biological explanations of Schizophrenia (2) Genetics

What does this mean? In pairs discuss and write up a conclusion based on this data Gottesman, (1991)

Role of genetics The fact that schizophrenia tends to run in families led to the inference that it has a genetic basis. 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. Concordance rates, which show the percentage of family members developing schizophrenia, are investigated as research evidence. The comparison is the 1% probability of schizophrenia in the general population. The greater the degree of genetic relatedness the higher the risk of developing the disorder, which suggests that there is a genetic link.

Research evidence: Twin Studies In twin studies the researchers want to establish the probability that the other twin is also has schizophrenia Gottesman’s (1991) analysis of twin studies revealed 48% concordance for monozygotic (MZ; identical) twins and only 17% for dizygotic (DZ; fraternal) twins.

Family studies Kendler (1985) has shown that first degree relatives of those with schizophrenia are 18 times more at risk than the general population. Gottesman and Bertelsen (1989) found that if one of your parents is an identical twin then you have a 17% chance of getting schizophrenia. Yet if your parent’s sibling has schizophrenia

Adoption studies Finnish adoption study (Tienari 1969) Adoptees had been separated from their mothers at 4 and the study concludes that 7% of the children who’s biological mothers had the disorder then developed it compared to 1.5% of adoptees who’s biological mothers did not have it. -this suggests genetics play a role in the development of schizophrenia.

Stop: Let’s Read Gottesman and Shield’s (1966) Study What is the diathesis stress model? What does this suggest about the genetic explanation?

Molecular Genetics McGuffin and Stuart (1980’s) HLA gene, a gene important in the body’s immune system was associated with Schizophrenia but no further research supported this. Hong (2001) TPH gene that is involved in the production of enzymes found variations in this gene in patients that had Schizophrenia. However Kelly and Murray (2000) suggest that each of the genes identified by molecular genetics is not innocent in itself, however people who inherit a number of them are at high risk of developing Schizophrenia.

Stop: Read Page 39 and 40, regarding Tiwari (2010) What do the findings suggest about the genetic explanation?

Tamminga and Schulz (1991) * Research has failed to isolate a single recessive or dominant gene that that seems to cause the illness.

Common Variants There are common variants that interact and alleles involved will be shared by unrelated individuals. Alleles: an alternative form of the gene, a gene can have more than one variant. This is possibly why twin studies show some evidence for genetic underpinning in Schizophrenia but do not uncover gene responsibility.

SODAR S: Supporting Evidence O: Opposing Evidence D: Different Theories A: Application R: Reductionist