biological explanations Flashcards
Genetic basis
Schizophrenia runs in families
Candidate genes
Describe Gottesman’s study
Relationship between degree of genetic similarity and shared risk of schizophrenia
48% identical twins
17% fraternal twins
How are genes responsible for inheritance of schizophrenia?
Number of genes = small increased risk of schizophrenia = polygenic
Aetiologically heterogeneous - different combos cause condition
Describe Ripke’s study
Combined data from genome studies
Genetic makeup of patients compared with controls
108 separate genetic variations associated with increased risk of SZ
What is the functioning of neurotransmitters in the dopamine hypothesis?
NTs work differently for schizophrenics
Dopamine involved
Dopamine - important in functioning of brain systems which are implicated in symptoms
What was the original dopamine hypothesis?
Hyperdopaminergia in subcortex (high levels of dopamine)
Excess of dopamine receptors in Broca’s area associated with poverty of speech
What is the new dopamine hypothesis?
Abnormal dopamine in cortex
Hypodopaminergia in prefrontal cortex - negative symptoms
What are neural correlates?
Measurements of structure or function of brain that correlate with schizophrenia
What is the ventral striatum?
Avolition = motivation loss
VS involved in anticipation of reward (motivation)
Abnormality in VS = avolition
What has been found about the neural correlates of negative symptoms?
Juckel - lower activity in ventral striatum in schizophrenics
Negative correlation between activity in VS and severity of negative symptoms
What are the neural correlates of positive symptoms?
Allen - scanned brains of those having auditory hallucinations
Lower activity levels in superior temporal gyrus and anterior cingulate gyrus
Evaluation - multiple sources of evidence for genetic susceptibility
Tienari study - still suffer from SZ even when adopted
Genetic factors make people more vulnerable
Evidence - mixed evidence for dopamine hypothesis
Dopamine agonists which increase dopamine make SZ worse
Antipsychotics decrease dopamine and work
However Ripke found genes which code for other NTs
Glutamate research is main focus
Evaluation - correlation causation problem
Does unusual activity cause symptoms
Negative symptoms may make less info pass through ventral striatum
Evaluation - role of mutation
Mutation in parental DNA can cause SZ without family history
Paternal sperm cell mutation
Positive correlation between paternal age and risk of SZ
Paternal age = increased risk of mutation
Fathers under 25 = 0.7%
Over 50 = 2%
