Biological explanations Flashcards
What is the genetic explanation of schizophrenia?
This explanation suggests that vulnerability to schizophrenia is inherited. This explanation states that genes or particular combinations of genes are passed on from parents to their children
What do family studies generally show?
That if you have a close family member with schizophrenia you are more likely to also develop schizophrenia
What has research shown about candidate genes in relation to schizophrenia?
There is no single gene that causes schizophrenia, instead it appears that a number of different genes are involved, and that schizophrenia is polygenic
What are the most likely genes that may cause schizophrenia?
Those coding for neurotransmitters including dopamine
What does research tend to show about the concordance of schizophrenia with twins?
That the concordance of schizophrenia is higher in MZ twins who share their entire DNA, than DZ twins who share 50% of their DNA - suggesting there is a genetic contribution
What sis Gottesman find?
Gottesman (1991) found that the likelihood of developing schizophrenia increased with genetic similarity, for example:
2nd degree relatives → 2-6%
1st degree relatives → 6-17%
Identical twins → 48%
What is a 1st degree relative and examples of them?
Share 50% of the same genes
- Parents, siblings, children, dizygotic twins
What is a 2nd degree relative and examples of them?
Share 25% of the same genes
- Half siblings, grandchildren, nephews/nieces, aunts/uncles
Who identified the C4 gene?
Sekar et al
What is the link between the C4 gene and schizophrenia?
Everyone has the C4 gene. Genetic analysis of 65,000 people found that those who had particular forms of the C4 gene (a variant of the gene) showed higher risk of developing schizophrenia
What is the role of the C4 gene?
C4 plays a role in pruning synapses but excessive pruning, by the particular variant of C4, could lead to the symptoms of schizophrenia
What does the role of the C4 gene say about schizophrenia?
It would explain why schizophrenia symptoms appear after adolescence and why the brains of people with schizophrenia have a thinner cerebral cortex with fewer synapses than healthy brains
What did Benzel et al do?
Benzel et al (2007) identified three genes: COMT, DRD4 and AKT1 and found that they have all been associated with excess dopamine in specific D2 receptors, leading to delusions and hallucinations in schizophrenic patients
What is the DRD gene?
Dopamine receptor density
Where is the COMT gene found and how does this link to schizophrenia?
The COMT gene is found in a region of the 22nd chromosome of the human genome and individuals with a deletion in this region (mutation) have 30x more likelihood of developing schizophrenia (Aburi, 2010)
What is hyperdopaminergia?
High dopamine activity
What is the role of dopamine?
Responsible for guiding attention
What does excess dopamine activity mean?
You will fail to selectively attend, meaning you experience sensory overload. The dopamine will not be distributed well - there may be too much dopamine activity in Broca’s area but not enough in the pre-frontal cortex
How is excess dopamine activity associated with schizophrenia?
It can lead to symptoms of schizophrenia
What is hypodopaminergia?
Low levels of dopamine activity
What does aetiologically heterogeneous mean?
Something has different causes
How is schizophrenia aetiologically heterogeneous?
Because different studies have identified different candidate genes it also appears that schizophrenia is aetiologically heterogeneous, suggesting that different combinations of factors, including genetic variation, can lead to the condition
