PLEASE COMPLETE AND HAND IN TO JODIE Year 13 lesson 1

Genetic Explanations That an individual may inherit genes that cause schizophrenia How can psychologist determine whether it is an individual’s genes that has caused schizophrenia?

Task 1 There are 5 types of genetic information which are shown on the following slide. Below that are different studies and 3 evaluation points. Place each of the studies under each of the titles. Write this information into your notes. If you have any questions please write in in the discussion area of the website.

Gene mapping Adoption studies Diathesis- stress model Family Studies Twin studies

This procedure involves comparing the genetic material from families who have schizophrenia with samples from families without schizophrenia to identify common factors

Sherrington et al (1988) found evidence for a cluster of genes on chromosome 5, which might make an individual susceptinle to schizophrenia.

Hahn et al. (2006) produced evidence that linked the gene associated with neuregulin with a predisposition for schizophrenia

This model suggest that schizophrenia is inherited and then life experiences trigger the condition

Studies with these sets of individuals provides psychologists with an important insight into genetics and schizophrenia. Monozygotic (MZ) share the same genes and are identical. Dizygotic (DZ) have approximately the same genes as any other brother or sister (approximately 50%)

Gottesman (1991) summarised about 40 studies, concluding that the concordance rate is about 48% for MZ twins but only 17% for DZ twins, indicating some environmental influence but a larger genetic component

Tienari (1991) reported on a Finnish adoption study following 155 adopted children whose natural mothers were schizophrenic. In adulthood 10.3% of those with schizophrenic mothers had developed schizophrenia compared to only 1.1% of those without schizophrenic mothers

Kendler et al (1985) found that first degree relatives of schizophrenics are 18 times more likely to be similarly diagnosed.

Parnas et al. (1993) followed 207 children (aged ) who had schizophrenic mothers. At a 27-year follow up 16% had been diagnosed as schizophrenic compared with 2% in a low-risk group.

High concordance rates in MZ twins may be because they are treated more similarly than DZ twins (Loehlin and Nichols, 1976)

Family similarities can also be explained by shared environmental influences

Less than 50% of children where one parent was schizophrenic develop the disorder (fish et al. 1992) The diathesis-model can be used to explain this

Genetic factors are involved but not solely responsible.