Biological Explanations For Schizophrenia COPY Flashcards
What conclusion did family studies reach regarding the genetic basis of SZ?
Risk of SZ increases when genes are similar to a relative with the disorder
How does the risk of schizophrenia change with genetic similarity to a relative?
Increases with genetic similarity:
* 2% if an aunt has it
* 9% if a sibling has it
* 48% if an identical twin has it
Gottesman conducted a large-scale family study demonstrating these statistics.
What is the term for the involvement of multiple genes in the risk of schizophrenia?
Polygenic
Early research aimed to find a single faulty gene but it was later established that multiple genes are involved.
What study was conducted regarding candidate genes of SZ?
Ripke et al combined all previous data from genome-wide studies, comparing genetic makeup of 37,000 SZ to 113,000 controls
108 separate genetic variations were associated with increased risk
What is the role of mutation in SZ?
SZ can appear in a family with no history likely due to sperm mutation as parents age
Brown et al found it increased from 0.7% in fathers under 25 and increased to 2% in fathers over 50
Which neurotransmitter is most commonly associated with schizophrenia?
Dopamine
Most likely genes involved in schizophrenia are those encoding for neurotransmitters including dopamine.
What did Ripke et al’s study reveal about genetic variations associated with schizophrenia?
108 separate genetic variations were associated with increased risk of schizophrenia
The study compared the genetic makeup of 37,000 schizophrenics to 113,000 controls.
What role do mutations play in the appearance of schizophrenia in families with no prior history?
Mutations can arise from radiation, poison, and infection
Positive correlation exists between paternal age and risk of schizophrenia.
What is the best-known neural correlate of schizophrenia?
Dopamine
Dopamine is important in the functioning of several brain systems related to the symptoms of schizophrenia.
What does the original dopamine hypothesis suggest about dopamine levels in schizophrenia?
Higher levels of dopamine in the sub cortex (hyperdopaminergia)
based on finding that antipsychotics = Parkinson’s-like symptoms which is associated with low dopamine levels
What is hypERdopaminergia?
Excess of dopamine levels
Excess dopamine receptors in Broca’s area = speech poverty or auditory hallucinations
What does the updated version of the dopamine hypothesis propose?
According to David et al, Involvement of both high (subcortical hyperdopaminergia) and low levels (cortical hypodopaminergia) of dopamine in different brain regions
low dopamine in the prefrontal cortex + genetic variations and early exposure to stress = sensitivity to subcortical hyperdopaminergia and cortical hypodopaminergia
Whats a strength of the genetic explanation for schizophrenia?
Strong evidence from family studies
* Gottesman’s study shows risk increase with genetic similarity
* Tienari et al’s findings on increased risk in biological children with SZ parents (even if theyve grown up elsewhere)
* Hilker et al’s concordance rate of 33% for identical twins and 7% for non identical
show some individuals are more vulnerable due to genetic factors.
What are limitations of the genetic explanation of schizophrenia?
Evidence of the role of environmental factors
Psychological influences such as:
* Traumatic birth
* Childhood trauma
Genetic factors cannot be the sole explanation
67% of individuals with SZ or other psychotic disorders reported at least one childhood trauma.
- 38% for control group
What are strengths of dopamine involvement in schizophrenia?
Support for dopamine involvement
Amphetamines increase dopamine and worsen symptoms
* Antipsychotics reduce dopamine activity and intensity
* Some candidate genes affect dopamine production
suggest a strong link between dopamine and schizophrenia symptoms.
What limitation exists in the dopamine hypothesis regarding other neurotransmitters?
Evidence for a central role of glutamate through post-mortem and live scanning studies of high levels of glutamate in various brain regions of SZ sufferers
Several candidate genes believed to be involved in glutamate production
Other neurotransmitters may be involved other than dopamine
What are strengths of dopamine hypotheisis?
Amphetamine stimulates dopamine nerve cells = dopamine flooding of synapse. Normal individuals taking them suffer SZ symptoms, disappear when they stop taking them
Tenn et al tested this with rats
What’s another strength of dopamine hypothesis regarding antipsychotics?
Antipsychotics block dopamine activity reducing activity in dopamine pathways, tested by Tenn et al with rats
Reduce positive symptoms and are classified as dopamine antagonists.
