Biological explanations for schizophrenia

Question 1

Biological explanations for schizophrenia

parts

Answer 1

Genetic basis of schizophrenia
Dopamine hypothesis
Neural correlates of schizophrenia

Question 2

Genetic basis of schizophrenia

parts

Answer 2

Inheritance - Gottesman (1991)

Candidate genes - Gottesman (1991

Question 3

Genetic basis of schizophrenia

Inheritance

Answer 3

└schizophrenia runs in families= weak link for genetic basis
└family tend to share environment as well as genes
└systematic investigations of the extent to which genetics is linked to schizophrenia
└Gottesman (1991)- large scale family study
└identical twins- 48%
└fraternal twins- 17%
└general population- 1%

Question 4

Genetic basis of schizophrenia

Candidate genes

Answer 4

└believed to be associated with risk of inheritance
└schizophrenia is polygenic
└influenced by multiple genes
└schizophrenia is aetiologically heterogeneous
└different combinations of factors can lead to the condition
└Stephen Ripke et al (2014)
└combined data from many genome- wide studies of schizophrenia
└genetic makeup of 37k compared to 113k controls
└108 separate genetic variations associated with increased risk of schizophrenia
└e.g. genes that coded for function of neurotransmitters like dopamine

Question 5

Dopamine hypothesis

parts

Answer 5

Neurotransmitters
Hyperdopaminergia in subcortex
Hyodopaminergia in prefrontal cortex - Goldman-Rakic et al (2004)

Question 6

Dopamine hypothesis

Neurotransmitters

Answer 6

└dopamine involved in schizophrenia
└dopamine: a neurotransmitter that generally has an excitatory effect and is associated with the sensation of pleasure
└usually high levels= schizophrenia, low levels= Parkinson’s disease

Question 7

Dopamine hypothesis

Hyperdopaminergia in subcortex

Answer 7

└original hypothesis
└high levels of dopamine in sub cortex of brain
└(central areas of brain)
└e.g. excess of dopamine in Broca’s area (responsible for speech production)
└associated with speech poverty/auditory hallucinations

Question 8

Dopamine hypothesis

Hyodopaminergia in prefrontal cortex

Answer 8

└more recent versions of hypothesis 
└Goldman-Rakic et al (2004)
  └low levels of dopamine in prefrontal cortex of brain
  └thinking decision making area
    └negative symptoms of schizophrenia

Question 9

Neural correlates of schizophrenia

parts

Answer 9

Neural correlates of negative symptoms - Juckel et al (2006)

Neural correlates of positive symptoms - Allen et al (2007)

Question 10

Neural correlates

definition

Answer 10

patterns of structure or activity in the brain that occur in conjunction with an experience and may be implicated in the origins of that experience

Question 11

Neural correlates of negative symptoms

Answer 11

└ventral striatumi involved in antipicipation of a reward
└=avolation (no motivation)
└Juckel et al (2006)
└measured activity levels in the ventral striatum in schizophrenia
└lower activity levels than controls
└negative correlation between activity levels in ventral striatum and severity of overall negative symptoms

Question 12

Neural correlates of positive symptoms

Answer 12

└Allen et al (2007)
└scanned brains of patients having auditory hallucinations vs control group
└whilst they identified pre-recorded speech of theirs/others
└lower levels in superior temporal gyrus and anterior cingulate gyrus in hallucination group (who also made more errors)

Question 13

Biological explanations for schizophrenia

strengths

Answer 13

Research support for genetic susceptibility
└Gottesman (1991)
└shows genetic similarity and risk of schizophrenia are closely related
└Pekka Tienari et al (2004)
└adoption study
└children of schizophrenia sufferers still at increased risk of schizophrenia even if adopted into non schizophrenic families
└Ripke et al (2014)
└study at molecular level
└particular genetic variations significantly increase the risk of schizophrenia
└=genetic susceptibility important
└although environmental factors also associated

Question 14

Biological explanations for schizophrenia
limitations
summary

Answer 14

Mixed evidence for dopamine hypothesis - Curran et al (2004), Lindstroem et al (1999), Ripke et al (2014), Moghaddam and Javitt (2012
May be correlation not causation
Role of mutation - Brown et al (2002)
Psychological explanations

Question 15

Biological explanations for schizophrenia
limitations
Mixed evidence for dopamine hypothesis

Answer 15

└Curran et al (2004)
└dopamine agonists like amphetamines that increase the levels of dopamine make schizophrenia worse and can cause schizophrenia-like symptoms in non sufferers
└antipsychotic drugs reduce dopamine activity (Tauscher et al ,2014)
└Lindstroem et al (1999)
└radioactive labelling studies
└chemicals that needed to produce dopamine are taken up faster in brains of schizophrenia sufferers than controls
└suggests they produce more dopamine
└dopamine doesn’t provide a complete explanation for schizophrenia
└Ripke et al (2014)
└some genes identified code for the production of other neurotransmitters
└neurotransmitters other than dopamine also important
└Moghaddam and Javitt (2012)
└research on the neurotransmitter glutamate

Question 16

Biological explanations for schizophrenia
limitations
May be correlation not causation

Answer 16

└ although there are neural correlates of both positive and negative schizophrenia symptoms
└unclear if unusual activity in region of brain (shown in studies) causes the symptom
└other explanations for correlation
└correlation between levels of activity in ventral striatum and negative symptoms of schizophrenia
└may be something wrong with striatum causes negative symptoms
└OR may be that negative symptoms cause less information to pass through striatum= reduced activity
└OR another factor may influence both negative symptoms and ventral striatum activity

Question 17

Biological explanations for schizophrenia
limitations
Role of mutation

Answer 17

└ schizophrenia can take place without hereditary links
└by mutation in parental DNA e.g. in paternal sperm cells
└from radiation, poison, viral infection
└Brown et al (2002)
└positive correlation between paternal age (associated with risk of sperm mutation) and risk of schizophrenia
└fathers under 25- 0.7%
└fathers over 50= 2%

Question 18

Biological explanations for schizophrenia
limitations
Psychological explanations

Answer 18

└ environmental/psychological factors also important as well as biological
└e.g. family functioning in childhood
└probability of developing schizophrenia even if your identical twin has it is less than 50%