Biological explanations Flashcards
Is schizophrenia genetic?
It has been noted to run in families. However this is quite weak evidence for a genetic link because family members tend to share aspects of the environment as well.
What are candidate genes?
Individual genes that are believed to be associated with inheritance.
Why is schizophrenia said to be polygenic?
Because it seems to require a number of factors or genes to work in combination, hence making it polygenic?
Why is schizophrenia said to be aetiologically heterogeneous?
Because different studies have identified different candidate genes, therefore a different combination of factors can lead to the condition, hence making it aetiologically heterogeneous.
What did Ripke do?
He carried out a hue study combining all previous data from genome-wide studies of schizophrenia. The genetic make-up of 37,000 patients was compared to that of 113,000 controls.
What did Ripke find?
He found that 108 separate genetic variations were associated with increased risk of schizophrenia.
What does the dopamine hypothesis say about neurotransmitters?
The brain’s chemical messengers appears to work differently in a patient with schizophrenia. Dopamine is important in the functioning of several brain systems that may be implicated in the symptoms of schizophrenia.
What does the dopamine hypothesis say about hyperdopaminergia in the subcortex?
The role of unusually high levels of dopamine in the subcortex, for example in the broca’s area (responsible for speech production), may be associated with poverty of speech and the experience of auditory hallucinations.
What does the dopamine hypothesis say about hypodopaminergia in the cortex?
Goldma-Rakic have identified a role for low levels of dopamine in the prefrontal cortex (decision-making and thinking) in the negative symptoms of schizophrenia.
What does the dopamine hypothesis conclude?
That both hyper and hypodopaminergia are correct explanations as high and low levels in different areas of the brain are involved in schizophrenia.
What is the evaluation for the biological explanations for schizophrenia?
Multiple sources of evidence for genetic susceptibility
Evidence for the dopamine hypothesis
The role of mutation
Environmental factors
Evaluation point for the biological explanations for schizophrenia: Multiple sources of evidence for genetic susceptibility
Strong evidence for genetic vulnerability to schizophrenia from a variety of sources.
The Gottesman study:
If they had who schizophrenic parents = 46%
One schizophrenic parent = 13%
Schizophrenic siblings = 9%
And Tiernari’s:
6.7% of adoptees with schizophrenic mothers had schizophrenia
2% of adoptees with non-schizophrenic mothers had schizophrenia
Therefore there is overwhelming evidence that for the idea that genetic factors make people more vulnerable to developing schizophrenia than others. It does not mean it’s entirely genetic, but the evidence suggests that genetic susceptibility is important.
Evaluation point for the biological explanations for schizophrenia: Evidence for the dopamine hypothesis
Drugs like amphetamines that increase the levels of dopamine make schizophrenia worse and can produce schizophrenia-like symptoms in non-sufferers.
Antipsychotic drugs, work by reducing dopamine activity.
Both drug studies suggest and important role for dopamine in schizophrenia.
Lindstroem found that chemicals needed to produce dopamine are taken up faster in the brains of schizophrenia suffers than controls, suggesting that they produce more dopamine.
Evaluation point for the biological explanations for schizophrenia: The role of mutation
Schizophrenia can take place in the absence of a family history of the disorder. One explanation for this is mutation in parental DNA, for example, in paternal sperm cells. Evidence for the role of mutation comes from a study showing positive correlation between paternal age (associated with increased risk of sperm and mutation) and risk of schizophrenia.
Increasing from 0.7% with fathers under 25 to over 2% in fathers over 50.
Evaluation point for the biological explanations for schizophrenia: Environmental factors
The evidence supporting the role of biological factors is overwhelming, but there is also evidence to suggest an important role of environmental factors. The probability of developing schizophrenia even if your identical twin has it is less than 50%.
