Biological Explanations for Schizophrenia

Question 1

Bio explanation for schizophrenia - increased rate w/ parent compared to general population

Answer 1

Gottesman reported:
SZ rates = 1% for general pop. but 6% with a parent w/ SZ

Question 2

Genetic basis - family studies - Gottesman (‘91)

Answer 2

Large scale study found 9% chance of developing SZ if your sibling does

while family members share environment, still indicates support of genetics

Question 3

Candidate genes

Answer 3

Polygenic - causes by several genes
Aetiologically heterogeneous - risk affected by diff combos

Ripke et al - combined all prev. data on genomes - found 108 separate genes associated with increased risk of SZ

Question 4

Concordance rates - Gottesman (‘91)

Answer 4

Concordance rate of 48% for MZ twins + 17% for DZ twins
- suggests genes must have an influence but not 100% => other factors have a role
- 2/3 with SZ have no relative with similar diagnosis

Question 5

Mutation - especially of parental DNA

Answer 5

In absence of family history, SZ can still occur
Brown et al (‘02) - correlation between parental age + increased risk of sperm mutation => higher SZ risk
- risk from 0.7% w/ father under 25 to 2% w/ fathers over 50

Question 6

(S) Research Support in Adoption Studies - Tienari et al (2004)

Answer 6

Biological children of parents w/ SZ still heightened risk when raised outside of bio family
Suggests => some are more vulnerable to SZ because of genetic make up

Question 7

(L) Evidence suggesting environment contribute to developing SZ - Morkved et al (2017)

Answer 7

Morkved et al (2017) - Found 67% w/ SZ + related psychotic disorders reported at least 1 childhood trauma compared to 38% in control group (w/o SZ)

Di Fasti et al (2017) - smoking THC rich cannabis is a risk factor for SZ

Suggests => genetic factors cannot provide complete explanation for SZ + is biologically reductionist

Question 8

Dopamine hypothesis - original version

Answer 8

Suggests SZ was linked to high levels of dopamine receptors in subcortex - Hyperdopaminergia
e.g. in Broca’s area caused +ve symptoms e.g. auditory hallucinations

Question 9

Dopamine Hypothesis - Recent

Answer 9

Davis et al - include Hypodopaminergia - low levels of dopamine in cortex is also linked to SZ’s -ve symptoms e.g. avolition

Suggested => cortical hypodopaminergia leads to subcortical hyperdopaminergia

Question 10

(S) Research evidence from effects of diff. dopamine related drugs

Answer 10

Curran et al (2004) - Amphetamines that increase dopamine levels can induce SZ symptoms

Tauscher et al (2014) - anti psychotic drugs, that reduce dopamine levels by blocking the receptors, reduce SZ symptoms

Strongly suggests => dopamine is correlated to SZ

Question 11

(L) Evidence for glutamate and serotonin link to SZ

Answer 11

McCutcheon et al (2020) - Post-mortems + live brain scans consistently found raised levels of glutamate in those w/ SZ

Suggests => several neurotransmitters may be involved in developing SZ + DA hypothesis is too simplistic