Biological Explanation Flashcards
What is the genetic basis of SZ (4 points)
- Family studies
-Candidate genes
-The role of mutation - Neural correlates
What family study supports SZ genetic basis?
They use family studies to find genetic similarity to relative with disorder. Gottesman (1991) used a large scale family study, someone with an aunt with SZ had 2% chance, 9% with sibling and 48% with identical twin. Show importance of genes
What did early research believe + what do we know now?
They looked for a single genetic variation as they believed one single faulty gene could explain SZ. “schizogene”. Now we see SZ as polygenic, most likely genes are those coding neurotransmitters
What study supports candidate genes as Bio Explanation?
Ripke et al (2014)- Metanalysis of genome- wide studies. Genetic makeup of 37,000 with SZ compared to control of 113,000. 108 separate genetic variations associated with increased risk of SZ. SZ is aetiologically heterogenous (different combination of factors lead to the condition).
What is the role of mutation?
SZ can also have a genetic origin in the absence of family history, mutation in parental DNA caused by radiation, poison or viral infection. Positive correlations between paternal age and risk of SZ (0.7% in 25 and 2% in 50)
What are neural correlates?
Patterns of structure or activity that occur in the brain in conjunction with an experience and may be implicated in the origins of that experience
What is the dopamine hypothesis?
Discovery of drugs to treat SZ (antipsychotics) cause symptoms similar to those with Parkinson’s associated with low DA levels. SZ may be result of high DA in subcortical areas in the brain.
What’s an example of DA hypothesis
An excess of DA receptors in pathways from the subcortex to the Broca’s area may explain specific symptoms of SZ like poverty of speech
What is the updated DA hypothesis
Davis et al proposed hypodopaminergia (abnormally low DA in the brains cortex). It has been suggested that cortical hypodopaminergia leads to subcortical hyperdopaminergia- so both high and low levels of DA are included, genetic variations and levels of stress can lead to both sub and cortical.
What is the strength and weakness for Genetic variations?
- Research support: Adoption studies such as Tienari et al show that biological children of parents with SZ are at a heightened risk even if they grow up in adoptive family, people are more vulnerable due to their genetic makeup
- Environmental factors: also increase risk of developing SZ. Such as, birth complications and smoking THC-rich cannabis in teenage years. 67% of people with SZ reported at least one childhood trauma as oppose to 38% of matched group
What is a strength and limitation of DA?
Evidence for dopamine: Amphetamines increase DA and worsen symptoms in people with SZ and induce symptoms in people without, some candidate genes act on production of DA or receptors. DA involved in symptoms of SZ
Central role of glutamate: post-mortem and scanning found raised levels of neurotransmitter glutamate in several brain region of people with SZ, equally strong case made for other NT
