Biological explanations for schizophrenia

Question 1

Genetic basis - Family studies

Answer 1

• Someone with an Aunt who has schizophrenia has a 2% chance of developing it
• Increasing to 9% if the person is a sibling
• And 48% if they are an identical twin
• Supports idea of the importance of genes in schizophrenia

Question 2

Genetic basis - Candidate genes

Answer 2

• SZ is polygenic
• In a study researchers combined all data from genome-wide studies of SZ - genetic make-up of 37,000 people with SZ was compared to a control group of 113,000 - 108 separate genetic variations were associated with increased risk of SZ
• Other studies have shown SZ is aetiologically heterogeneous

Question 3

Genetic basis - Role of mutation

Answer 3

• Research showed a positive correlation between paternal age and risk of SZ
• Increasing from 0.7% with fathers under 25 to 2% in fathers over 50

Question 4

Neural correlates - Original dopamine hypothesis

Answer 4

• States the brains of people with SZ produces more dopamine than the brain of a ‘normal’ person
• Hyperdopaminergia - in subcortical areas of the brain e.g Broca’s area so may experience speech poverty and/or auditory hallucinations

Question 5

Neural correlates - Updated version of the dopamine hypothesis

Answer 5

• Now believed that people with SZ have abnormally low levels of dopamine than the brain of a ‘normal’ person
• Hypodopaminergia - in prefrontal cortex of the brain - could result in negative symptoms
• Has been suggested that hypodopaminergia leads to hyperdopaminergia

Question 6

Genetic explanations - evaluation - strength

Answer 6

• Strong evidence base for family studies
• Shows risk increases with genetic similarity to a family member with SZ
• Adoption studies show that biological children of parents with SZ are at heightened risk even if they grow up in an adoptive family

Question 7

Genetic explanations - evaluation - limitation

Answer 7

• Evidence to show environmental factors also increase risk of SZ
• Factors include biological + psychological influences
• Bio = birth complications
• Psycho = childhood trauma - research has found 67% of people with SZ reported at least 1 childhood trauma

Question 8

Neural explanations - evaluation - strength

Answer 8

• Research support
• Idea that dopamine is involved in SZ and induces symptoms in people without it
• 1st drugs increase dopamine and worsen symptoms in people with SZ and induce people without
• But 2nd drugs reduce dopamine activity and reduce intensity of symptoms
• Also some candidate genes act on the production of dopamine or dopamine receptors

Question 9

Neural explanations - evaluation - limitation

Answer 9

• Evidence for a central role of glutamate
• Post mortem studies have found raised levels of the neurotransmitter glutamate in several brain areas of people with SZ
• In addition, several candidate genes for SZ are believed to be involved in glutamate production or processing