Schizophrenia - Biological Explanations Flashcards
What is a genotype?
The set of genes carried by an individual
Define monozygotic twins
Identical twins formed when a single egg is fertilised by a single spermatozoon and then splits.
Define schizoid.
A disorder that resembles schizophrenia but does not involve psychotic symptoms e.g. loss of reality
Evaluate the dopamine hypothesis.
+ Iverson: found an excess if dopamine in the brain of schizophrenics (post mortems)
- Davis et al: clozapine, which does not reduce dopamine levels, is an effective drug for schizophrenia .
- too simplistic and reductionist
Describe and evaluate a family study investigating schizophrenia.
Gottesman
Concordance rates: 46% both parents
16% one parent
8% one sibling
1% general population
Strengths: provides support for genetic link
Weaknesses: family member spend more time together (nature v nurture)
Describe and evaluate a twin study investigating schizophrenia
Gottesman & Shields meta analysis
MZ: 48%, DZ:17%
Weaknesses: conc. rates not 100%, also hard to generalise due to small scale of study
What is the dopamine hypothesis?
The theory that increased dopamine in the brain results in schizophrenia.
What is the issue In using post mortems when investigating schizophrenia?
They cannot establish cause and effect and often involve ethical issues
What are arguments against the view that MZ conc. rates are high due to greater environmental similarity?
Lytton - MZ are similarly treated by both parents
Shields - Conc. rates for MZ raised apart are still similar to those raised together
Describe and evaluate an adoption study investigating schizophrenia.
Kety & Ingram
Higher rate of schizophrenia in biological relatives of schizophrenic children (20.3%/5.3%)
Weaknesses: nature v nurture must be taken into account
Evaluate the genetic explanation of schizophrenia
+ genes may be responsible for some types e.g. Stirling & Hallewell found that some with schiz. do not have close relatives with it.
+ higher rates among MZ with severe schiz. (Gottesman & Shields)
- studies tend to be retrospective or prospective, diagnostic criteria is ever changing and it is therefor hard to more parents with children
- environment cannot be completely ignored
What is the diathesis stress model?
Suggests that genes predispose individuals to schizophrenia but it is then triggered by a stressful life event
Define dizygotic twins.
Twins formed when two separate eggs are fertilised by two spermatozoa. Also known as fraternal twins
