Biological Explanations

Question 1

Dopamine Receptor Genes (D2 & DRD2)

Answer 1

• Affects number of dopamine receptor sites (too many = too sensitive)
• Transport proteins for dopamine
• Associated with both positive & negative symptoms (Davis & Khan, 1991)

Question 2

Glutamate Receptor Genes (NMDA/AMPA)

Answer 2

• Affect number of Glutamate receptor sites (too many)
• Especially important in ventral striatum (part of basal ganglia)
• Causes exhaustion & death of cells
• Associated with Negative symptoms (Sorg et al, 2013)

Question 3

G-Protein Coupled Receptor Kinase (GRK)

Answer 3

• Makes epigenetic & sensitivity changes to receptors for a number of excitatory neurotransmitters
• Higher levels increase effects (Funk et al, 2014)

Question 4

Family: Gottesman et al (1991)

Answer 4

• Studies concordance rates in children with SZ parents or siblings
• 2x SZ parents = 46%
• 1x SZ parent = 13%
• 1x SZ sibling = 9%

Question 5

Twins: Joseph (2004)

Answer 5

• Meta-analysis of data on MZ & DZ twin concordance for SZ
• MZ (identical) = 40%
• DZ (non-identical) = 7%
• Modern studies use blind researchers - show lower, but still big, difference

Question 6

Adoption: Tienari et al (2000)

Answer 6

• Compared siblings raised together v. apart
• 164 adoptees had SZ mothers = 6.7% developed SZ
• 197 adoptees in control group = 2% developed SZ
• Genetic liability for SZ is ‘decisively confirmed’

Question 7

The Dopamine Hypothesis

Answer 7

SZ is caused by imbalances of dopamine
Either:
* Too many D2 receptors
* D2 receptors are too sensitive/fire too often
* Produce too much dopamine
Explains positive symptoms only

Question 8

Actions of Dopamine

Answer 8

• Dopamine’s actions in the brain = Dopaminergia
• Too much = Hyperdopaminergia
• Too little = Hypodopaminergia

Question 9

Effects of Hyperdopaminergia

Answer 9

• In subcortex (limbic system) = associated with positive symptoms
• Broca’s area produces speech - too much dopamine here leads to speech/hearing related symptoms

Question 10

Effects of Hypodopaminergia

Answer 10

• In cortex = negative symptoms
• PFC is central executive (cognitive processes/decisions) - too little here leads to avolition/catatonia

Question 11

Drugs that increase dopaminergic activity

Answer 11

• Amphetamines
• L-Dopa (Grilly, 2002)

Question 12

Drugs that decrease dopaminergic activity (antipsychotics)

Answer 12

• Chlorpromazine reduces activity of dopamine
• Clozapine acts on dopamine and serotonin

Question 13

Davis & Khan (1991)

Answer 13

Put all findings together and suggested:
* Too much dopamine in mesolimbic pathway = positive symptoms
* Too little dopamine in prefrontal cortex = negative symptoms