Biological Explanations for SZ: Genetic

Question 1

outline the genetic explanation for SZ

Answer 1

One biological explanation of SZ is the genetic explantation.

SZ is passed on from one generation to the next through genetic inheritance.

So, the more closely related the family member is to the schizophrenic, the greater their chance of developing the disorder.

Argue no one gene is responsible for the development of SZ, it is more likely that different combinations of genes make individuals more vulnerable to the disorder (SZ is polygenetic)

Evidence comes from family studies, twin studies and adoption studies.

Used to establish a concordance rate (degree to which relatives share the same disorder).

Eg, identical (monozygotic) and non-identical (dizygotic) twins where one of each twin pair has SZ can be compared to see how often the other twin also shows the illness.

If SZ is genetic then monozygotic (MZ) twins should have higher concordance rates for the disorder than dizygotic (DZ) twins because they share 100% rather than 50% same DNA.

Question 2

evaluate the genetic explanation for SZ: STRENGTHS

Answer 2

P) support from family studies: Varma (1997)
E) 16% of the first-degree relatives of developed SZ compared to 7% of the controls
L) the more genetically related you are to someone w/ SZ, the more likely you are to develop SZ
E) BUT it is possible that the increased rate of SZ amongst those with parents with SZ was due to environmental rather than genetic influence

P) support from twin research: Joseph (2004)
E) MZ twins CR 40%, but 7% for DZ twins.
L) SZ may be partly genetic, but CR for MZ twins are not 100% so there must be other possible explanations for the development of SZ
E) possible that the higher concordance rates in MZ twins were the result of being treated more similarly than DZ twins, making it hard to rule out environmental factors as an explanation

P) support from adoption research: Tienari et al (2004)
E) compared adopted children whose biological mother had SZ to a control group of adoptees without any genetic risk
E) much higher rate of SZ amongst those whose biological mothers had SZ
L) even when the environmental influence of the biological mother was removed, the genetic risk was still evident.
E) BUT, found that a ‘healthy’ adoptive family could protect against those with a high genetic risk developing SZ -> environment does also play a role

Question 3

evaluate the genetic explanation for SZ: LIMITATONS

Answer 3

P) biological explanations = determinist
E) suggest SZ is caused by factors (neural correlates or genes) outside of sufferers conscious control
(can be viewed both positively and negatively)
E) + more humane because it removes blame from the patient for developing SZ
E) - if an individual feels they have no control over developing the disorder they could engage in risk behaviours eg (substance abuse) which could trigger the onset

P) biological explanations = reductionist
E) focus wholly on internal factors (e.g. genes and neurochemistry) and ignore environmental factors
E) there are psychological explanations of SZ such as family explanations which argue that the way parents treat their child is the main influence SZ onset.
L) limited: biology alone may not explain all aspects of SZ