Biological explanations - genetics Flashcards
What is the genetic theory?
We inherit 50% of our genes from each parent, and these build our bodies, especially the brain which is the source of all mental states
How could schizophrenia have a genetic basis?
It is a disorder of the mental state, which is affected by the brain and genes so could be heritable
What was the original belief about the cause of schizophrenia?
It could be entirely genetic
What is the modern believe about the cause of schizophrenia?
Most see genes as the diathesis in the diathesis-stress model
What have family studies found about schizophrenia?
That schizophrenia runs in families to some extent
What have twin studies and adoption studies tested?
The effect of genes
How can a genetic component of schizophrenia be found?
By identifying specific candidate genes and what they do
What was the original belief about genes and schizophrenia?
There could be a gene for schizophrenia
What is the modern belief about genes and schizophrenia?
Schizophrenia is polygenic so it involves multiple genes
How do genes link to the dopamine hypothesis?
Many of the candidate genes for schizophrenia code for the neurotransmitter dopamine
How do we test for candidate genes?
Studies of molecular genetics
What is research evidence for the genetic explanation of schizophrenia?
Gottesman’s meta-analysis
What were Gottesman’s innings?
The concordance rate for DZs was 48% and 17% for MZs
What were the conclusions of Gottesman’s meta analysis?
There was a large difference, so there is a moderate to strong effect of genes
What is the logic of twin studies?
Siblings have 50% in common and different ages, so environment is similar but different, whereas MZs have 100% of genes in common, but DZs have 50%, do DV is relatedness and is a natural experiment
What do twins studies control?
Environment, as both twin are raised together at the same time so are very similar
What is a strength of twin studies?
They enhance the scientific credibility of genetic theory as evidence is better is more controlled and there is more of it
What are the strengths of Gottesman’s meta-analysis?
Shows a pattern of data across studies, merging data reduces the effect of variation, estimates of concordance rates are likely to be accurate and enhances scientific credibility of genetic theory
What are the limitations of twin studies?
MZs are treated more similarly than DZs, twin studies may exaggerate influence of genetics and reduces scientific credibility of genetic theory
What is research evidence for adoption?
Tienari’s adoption study
What were Tienari’s findings?
Concordance rate between biological mothers with sz and their adopted away offspring was 7%, and concordance rate of adopted away offspring without sz was 1.5%
What were the conclusions of Tienari’s study?
There was a reasonable size difference so moderate effect
What are strengths of adoption studies over twin studies?
There is full separation of genetic and environmental influences so is strong evidence, enhancing scientific credibility of genetic theory
What are strengths of twin studies and adoption studies?
Findings have been replicated many times, so triangulated evidence from different types of research, enhancing scientific credibility of genetic theory
What is the interactionist approach to explains schizophrenia?
The diathesis stress model
What is the issue with twin and adoption studies evidence?
The concordance rates are too low for it to be entirely genetic
What is the issue with the genetic theory?
It is incomplete otherwise concordance would be much higher so no single factor explains schizophrenia, such as genes and family stressors
What the issue with the environmental explanation?
It can’t be complete or rates of schizophrenia would be much higher as stressors are common
How do stressors affect schizophrenia?
They only trigger schizophrenia in already genetically vulnerable people, genes don’t lead to schizophrenia in those with low stressors
What is the polygenic model?
Schizophrenia is due to multiple genes and is a better alternative to the single gene view
What is evidence for the polygenic model?
Ripke’s meta-analysis
What were the findings of Ripke’s meta-analysis?
108 genes link to SZ, often including genes linked to dopamine reduction, with only each risk gene increasing the risk by a small amount
What were the findings of Ripke’s meta-analysis?
108 genes link to SZ, often including genes linked to dopamine reduction, with only each risk gene increasing the risk by a small amount
