Schizophrenia - Biological Explanations Flashcards
Diathesis stress model researcher?
Gottesman and Reilley
Gottesman and Reilley?
Many people have a biological predisposition for SZ which is triggered by psychological stressors
Biological explanations for SZ?
Genetic factors and the dopamine hypothesis
Genetic factors are looked at in…
family studies, twin studies and adoption studies
Family study on SZ?
Gottesman
Gottesman?
46% chance if both parents had SZ, 13% if one parent, 9% if a sibling had it and 1% chance for general population (40 european studies)
Kety et al? (f)
20+ year study diagnosed SZ in 16.2% of the high risk group (mothers with SZ) and 1.9% of the low risk group, even when matched
Twin study on SZ?
Gottesman and Shields
Gottesman and Shields?
42% concordance rate for hospitalisation and diagnosis for MZ twins, 9% for DZ twins (57 twin pairs)
Adoption study on SZ?
Kety et al
Kety et al? (a)
High rates of diagnosis for chronic SZ in adoptees whose parents had the same diagnosis, despite being adopted by ‘healthy’ parents
Weaknesses of genetic factors in SZ?
Methodological problems
Reductionist
Ignores nurture
Strengths of genetic factors in SZ?
Support
Supporting evidence for genetic factors in SZ?
Kety et al
Methodological problems in genetic factors in SZ?
Most studies have broadened definition of SZ to include non-psychotic ‘SZ spectrum disorders’
Research on SZ spectrum disorders?
Kety et al found no full cases of SZ among 1st degree relatives of children with SZ spectrum disorders
Reductionism in genetic factors in SZ?
May be more to do with common rearing patterns or other factors such as EE
Research on EE?
Kalafi and Torabi
Kalafi and Torabi?
High EE was one of the main causes of SZ
Ignoring nurture in genetic factors in SZ?
Joseph
Joseph?
MZ twins treated more similarly, encounter more similar environments and experience more identity confusion
Main belief of the dopamine hypothesis?
SZ results from an excess of dopamine activity at certain synaptic sites
Reasons for excess of dopamine activity?
- release of excess dopamine by presynaptic neurone firing too easily or too often
- abnormally high excess of DZ receptors -> more dopamine binding -> more firing
Research on dopamine hypothesis?
Comer
Comer?
Dopamine neurones play a key role in guiding attention, so disturbances may lead to attention, perception and thought problems
Ways of investigating dopamine hypothesis?
Aphetamines, antipsychotic drugs, parkinsons disease
What approach does the dopamine hypothesis come from?
Biochemical
What do amphetamines do?
Dopamine agonists - result in hallucinations and delusions
What to antipsychotic drugs do?
Dopamine antagonists - eliminate SZ symptoms
Research on parkinsons disease?
Grilly
Grilly?
Sufferers of parkinsons disease have low levels of dopamine, so taking L-dopa to raise levels makes them develop side-effecs of SZ type symptoms
Strengths of the dopamine hypothesis?
Support
Effective treatments
Weaknesses of the dopamine hypothesis?
Reductionist
Cause or effect?
Weak evidence
Support for dopamine hypothesis?
Seeman
Seeman?
Increase in dopamine receptor density between 60-110% in SZs
Effective treatments from the dopamine hypothesis?
Davis et al
Davis et al?
55% relapse rates for those on placebo, 19% for those an antipsychotics
Reductionism in dopamine hypothesis?
Vaughn and leff
Vaughn and leff?
Antipsychotics only made a significant difference for those with high EE (53% relapse compared to 12%)
Cause or effect in dopamine hypothesis?
Haracz
Haracz?
Those who hadn’t received medication had normal levels of dopamine in post-mortems
Weak evidence for dopamine hypothesis?
Copolov and Crook
Copolov and Crook?
PET scans yet to find convincing evidence
