Biological explanations Flashcards
(18 cards)
What did family studies confirm?
The risk of schizophrenia increases in line with genetic similarity to a relative with the disorder.
Who presented findings for family studies?
Gottesman
Using a large scale
What are examples of Gottesmans findings?
Sibling - 9%
Identical twin - 48%
Aunt - 2%
What did early research for candidate genes look into?
A single genetic variation in the belief that one fault gene could explain schizophrenia
What does it mean if Schizophrenia is polygenic?
It is influences by multiple genes
What did Ripke et al find about candidate genes?
Combined all previous data from genome-wide studies
Genetic make up of 37000 people with diagnosis of schizophrenia
Compared to 113000 controls
108 separate genetic variations were associated with slightly increased risk of schizophrenia
What has it meant that different studies have identified different candidate genes?
Schiz appears to be aetiologically heterogenous
Different combinations of factors
Including genetic variation can lead to the condition
What is the role of mutation?
Mutation in parental DNA
Caused by radiations, poison or viral infection
What is evidence of the role of mutation?
Positive correlations between paternal age (increased risk of sperm mutation) and risk of schizophrenia
Increasing from around 0.7% with fathers under 25 - 2% in fathers over 50
What is a strength for genetic explanations?
Strong evidence based
Adoption studies like Tienari et al
Biological children of parents with schizophrenia are at heightened risk even if they grow up with an adoptive family
Hilker et al
Twin study
Concordance rate of 33% for identical twins and 7% non identical twins
Shows people are more vulnerable to schizophrenia as a result of their genetic make up
What is a limitation of the genetic explanation ?
Environmental factors
Increase risk of developing schizophrenia
Biological and psychological influences
Bio - Birth complications and smoking THC- rich cannabis in teen years
Psych - Childhood trauma which leaves ppl more vulnerable to adult mental health problems in general
What did Morkved et al find about environmental factors?
67% of people with schizophreniaz and related psychotic disorders reported at least one childhood trauam
Opposed to 38% of matched group with no psychotic mental health issues
Genetic factors alone cannot provide a complete explanation for schizophrenia
What is the best neural correlate of schizophrenia?
Neurotransmitter dopamine
Important in the functions of several brain systems related to the symptoms of schizophrenia
What is the original dopamine hypothesis?
Discovery that drugs used to treat schizophrenia causes symptoms similar to those in people with Parkinson’s disease (condition associated with low DA)
Eg. antipsychotics which reduce dopamine
Schiz may be result of high levels of DA in subcortical areas of the brain
Hyperdopaminergia
Eg. access of DA receptors in pathways from subcortex to brocas area (responsible for speech production) may explain scientific symptoms of schizophrenia - poverty or speech
What did davis et al propose?
Addition of cortical hypodopaminergia in the brain cortex
Explains symptoms of schizophrenia aswell
Eg. low DA in profrontal cortex (responsible for thinking) - explains cognitive problems like negative symptoms
Cortical hypodopaminergia leads to subcortical hypodaminergia - high and low leavels of DA in different brain regions part of updates dopamine hypothesis
What does the updated dopamine hypothesis also explain?
Origions of abnormal DA function
Both genetic variates and early experiences of stress both psychological and physical
Make some people more sensitiive to cortical hypodopaminergia and hence subcortical hyperdopaminergia
What is a strength for dopamine?
Evidence for dopamine
1 - Amphetamines increase DA and worsen symptoms in people with schizophrenia
Induce symptoms in people without
2 - Antipsychotic drugs reduce DA activity - reduce the intensity of symptoms
3 - Some candidate genes act of production of DA or DA receptors
Strongly suggesting dopamine is involved in the symptoms of schizophrenia
What is a limitation of dopamine hypothesis?
Evidence for central role of glutamate
Post mortem and live scanning
Consistently found raised levels of neurotransmitter glutamate in several brain regions of people with schizophrenia
Several candidate genes for schiz are believed to be involved in glutamate production or processing
Meaning equally strong case can be made for a role for other neurotransmitters
