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Biological Explanations Of Schizophrenia Notes

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Biological explanations of schizophrenia


Dopamine levels - bio-chemical o Does dopamine encourage schizophrenia or does schizophrenia encourage enhanced levels of dopamine?
Brain structure o Same problem as before Genetic inheritance o Predisposition Flu virus o Likelihood that child will develop schizophrenia if mother has flu while pregnant Brain damage Infection Other bio-chemical imbalances Evolutionary explanation o Survival value in having schizophrenia, which could have developed over time o Reaction to cognitive pressure, so schizophrenia is a way of dealing with it

Genetic inheritance:

DNA inherited from biological parents Twin, family and adoption studies Twin studies o MZ/ monozygotic twins - identical, same egg splits o DZ/ dizygotic twins - non-identical, different eggs o Concordance rate is percentage between a twin having schizophrenia if the other one has it Adoption studies o Look at people who have been brought up out of a family environment o More likely it is down to genetics rather than environmental factors if child inherited schizophrenia from parents o Want twins who have been adopted at birth by different people o Difficulty with finding out about biological parents

o Problem if adopted child still visits schizophrenic parents - learn behaviour

Twin studies:

Cardno et al 1999 found 40% concordance rate in MZ twins compared to 5.3% in DZ twins o Tells us schizophrenia can be inherited because concordance rate for MZ twins are much higher because they have more genetic similarities than DZ twins, who do not have as much in common o DZ twins still provide support because there is a higher concordance rate then the prevalence of 1% of the population Gottesman 1991 meta-analysis of 40 studies found 48% for MZ twins and 17% for DZ twins o Good reliability since lots of studies have the same result and bigger pool of data from a meta-analysis o However, some people will have been used more than once because there's such a limited number of people, so they have to be re-used throughout studies o Inconsistency between studies, so creates problems when comparing dissimilar studies due to cultural variation, procedure and interpretation Torrey 1992 found MZ twins had 28% concordance rate and 6% for DZ twins in 8 studies of better quality design o Studies were better designed, so more representative of all data than Gottesman Joseph 2003 found 22.4% for MZ twins and 4.6% for DZ twins using the nine most recent studies Variation between studies means problems with validity and reliability Could be other reasons for schizophrenia Different definitions of schizophrenia Small sample sizes in some studies, so percentages can change a lot very easily Can't control gender because it would further limit the sample Consistently showing that MZ twins have a higher concordance rate

Family studies:

Gottesman 1991 o Both parents - 46% chance o One parent - 16%

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