Biological explanations of schizophrenia

Biological explanations

The genetic basis of schz

• It has been noted for many years that schz runs in families
• This is quite weak in itself for a genetic link because family members tend to share aspects of their environment as well as many of their genes
• There is a strong relationship between the degree of genetic similarity and shared risk of schz

• Candidate genes
• Individual genes are believed to be associated with the risk of inheritance
• Because a number of genes each appear to confer a small increased risk of schz it appears that schz is polygenic (it requires a number of factors to work in combination)
• Because different studies have identified different candidate genes it also appears that schz is aetiologically heterogeneous (different combinations of factors can lead to the condition)
• Ripke carried out a huge study combining all previous data from genome-wide studies of schz
• The genetic make up of 37,000 patients was compared to that of 113,000 controls: 108 separate genetic variations were associated with increased risk of schz
• Genes associated with increased risk included those coding for the functioning of a number of NTs e.g dopamine

The dopamine hypothesis

• Neurotransmitters
• The brain's chemical messengers appear to work differently in the brain of someone with schz
• Dopamine is widely believed to be involved
• Dopamine is important in the functioning of several brain systems that may be implicated in the symptoms of schz

• Hyperdopaminergia in the subcortex
• Original version of the dopamine hypotheis focused on the possible role of high levels/ activity of dopamine in the subcortex (central areas of the brain)
• E.g an excess of dopamine receptors in Broca's area may be associated with poverty of speech and/or experience of auditory…