PAPER 3 - SCHIZOPHRENIA - biological explanations for schizophrenia

Question 1

what are the biological explanations for schizophrenia?

Answer 1

• genetics - family studies, candidate genes, mutations
• neural correlates

Question 2

how can family studies be used as a genetic explanation of schizophrenia?

Answer 2

• Gottesman did a large scale study, found if you have an aunt with SZ you have 2% chance of developing the disorder, sibling = 9% chance, identical twin = 48%
• Tienari found that of 164 adoptees with schizophrenic biological mothers, 11 also received diagnosis of SZ compared to 4 of 197 control adoptees (normal mothers)

Question 3

how can candidate genes be used as an explanation of schizophrenia?

Answer 3

Ripke looked at 37,000 schizophrenics and 113,000 controls, found 108 variations of genes associated with increased risk of SZ

Question 4

how can mutations be used as an explanation of schizophrenia?

Answer 4

• schizophrenia can also be developed in individuals who have no family history of the disorder
• could be due to a gene mutation in the DNA of a parent caused by radiation or viral infection
• positive correlations between paternal age & schizophrenia, risk has increased from 0.7% with a father under 25 to over 2% in fathers over 50

Question 5

what is the dopamine hypothesis?

Answer 5

• theory was developed when it was found that antipsychotics used to treat schizophrenia caused symptoms similar to Parkinson’s disease
• Parkinsons sufferers given “L-Dopa” to increase dopamine (D2) have been found to develop schizophrenia type symptoms
• thought schizophrenia might be a result of high dopamine
• lots of D2 receptors on receiving neurons causes more neurons firing faster, leads to hallucinations/delusions

Question 6

what is the revised hypothesis?

Answer 6

• cortical hypOdomapinergia (low DA in brains cortex) e.g low DA in prefrontal cortex (used for thinking) could explain negative symptom of cognitive problems
• cortical hypOdopaminergia leads to subcortical hypERdopaminergia, so both high and low DA in different parts of the brain are part of revised hypothesis
• also includes psychological origins (stress) and make people more vulnerable to cortical hypOdopaminergia and subcortical hypERdopaminergia

Question 7

what are the neural correlates of negative symptoms?

Answer 7

• avolition: loss of motivation which is associated with ventral striatum area of the brain
• abnormality here develops avolition
• research found that lower levels of activity in ventral striatum of sch. sufferers than controls
• therefore negative correlation between activity levels in VS & severity of symptoms

Question 8

what are the neural correlates of positive symptoms?

Answer 8

• hallucinations: lower activity levels in superior temporal gyrus found in schizophrenics who had auditory hallucinations, when they were asked to identify speech as either their own or others compared to controls activity level
• therefore reduced activity in superior temporal gyrus is a neural correlate of auditory hallucinations

Question 9

what are the evaluation points for genetics to support the biological explanation for schizophrenia?

Answer 9

• Gottesman shows that risk increases with genetic similarity to a family member with schizophrenia
• Tienari shows that biological children of parents with schizophrenia are at more risk even if they grew up in adoptive family
• Hilker showed concordance rate of 33% for identical twins, 7% non-identical twins

Question 10

what are the evaluation points for genetics to criticise the biological explanation for scizophrenia?

Answer 10

• Joseph said MZ twins encounter more similar environments than DZ twins and experience more ‘identity confusion’ which suggests concordance rates between DZ and MZ twins reflect nothing more than environmental factors
• adoptees may be selectively placed, it is extremely unlikely that the children born to women with schizophrenia would’ve been placed in the same adoptive families as children without that background
• this coupled with other adoption studies mean we cant accept conclusions about the role of genetics in schizophrenia

Question 11

what are the further evaluation points for the role of genetics in schizophrenia? (environmental factors)

Answer 11

• environmental factors include biological and psychological influences
• biological: birth complications and smoking THC-rich cannabis in teenage years
• psychological: childhood trauma leaves people more vulnerable to adult mental health problems

Question 12

how is neural correlates support for the influence of grey matter deficits?

Answer 12

• support for significance of grey matter deficits in SZ comes from a meta-analysis
• they analysed results of 19 studies, patients with SZ compared to healthy controls showed higher reduction in cortical grey matter volume over time
• this pattern of grey matter reduction was specific to discrete cortical areas in the frontal, temporal and parietal lobes

Question 13

what are the criticisms for neural correlates?

Answer 13

• researchers claim there is strong evidence against both original and revised dopamine hypothesis
• argued that antipsychotic drugs do not alleviate hallucinations and delusions in 1/3 of people experiencing symptoms
• also found that hallucinations and delusions are present despite levels of dopamine being normal
• suggests other neurotransmitter systems acting independently may also produce positive symptoms associated with SZ