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BIOLOGICAL
EXPLANATIONS OF
SCHIZOPHRENIA (2)
Genetics
What does
this mean?
In pairs discuss and
write up a conclusion
based on this data
Gottesman, (1991)
ROLE OF GENETICS
• The fact that schizophrenia tends to run in families led to the inference that it
has a genetic basis.
• According to the genetic hypothesis, the more closely related the family
member to the person with schizophrenia the greater their chance of
developing the disorder.
• Concordance rates, which show the percentage of family members
developing schizophrenia, are investigated as research evidence. The
comparison is the 1% probability of schizophrenia in the general population.
• The greater the degree of genetic relatedness the higher the risk of
developing the disorder, which suggests that there is a genetic link.
RESEARCH EVIDENCE: TWIN
STUDIES
• In twin studies the researchers want to establish the probability that the other
twin is also has schizophrenia
• Gottesman’s (1991) analysis of twin studies revealed 48% concordance for
monozygotic (MZ; identical) twins and only 17% for dizygotic (DZ; fraternal)
twins.
FAMILY STUDIES
• Kendler (1985) has shown that first degree relatives of those with
schizophrenia are 18 times more at risk than the general population.
• Gottesman and Bertelsen (1989) found that if one of your parents is an
identical twin then you have a 17% chance of getting schizophrenia. Yet if
your parent’s sibling has schizophrenia
ADOPTION STUDIES
Finnish adoption study (Tienari 1969)
Adoptees had been separated from their mothers at 4 and the study
concludes that 7% of the children who’s biological mothers had the disorder
then developed it compared to 1.5% of adoptees who’s biological mothers
did not have it.
-this suggests genetics play a role in the development of schizophrenia.
STOP: LET’S READ GOTTESMAN AND
SHIELD’S (1966) STUDY
What is the diathesis stress model?
What does this suggest about the genetic explanation?
MOLECULAR GENETICS
McGuffin and Stuart (1980’s) HLA gene, a gene important in the body’s
immune system was associated with Schizophrenia but no further research
supported this.
Hong (2001) TPH gene that is involved in the production of enzymes found
variations in this gene in patients that had Schizophrenia.
However
Kelly and Murray (2000) suggest that each of the genes identified by
molecular genetics is not innocent in itself, however people who inherit a
number of them are at high risk of developing Schizophrenia.
STOP: READ PAGE 39 AND 40,
REGARDING TIWARI (2010)
What do the findings suggest about the genetic explanation?
Tamminga and Schulz (1991)
* Research has failed to isolate a single recessive or dominant gene that that
seems to cause the illness.
COMMON VARIANTS
There are common variants that interact and alleles involved will be shared by
unrelated individuals.
Alleles: an alternative form of the gene, a gene can have more than one
variant.
This is possibly why twin studies show some evidence for genetic underpinning
in Schizophrenia but do not uncover gene responsibility.
SODAR
S: Supporting Evidence
O: Opposing Evidence
D: Different Theories
A: Application
R: Reductionist
HOMEWORK
The Non-biological explanation for
Schizophrenia: The Social Causation hypothesis
• And the article called: ‘Social and cultural explanations for
the increased incidence of schizophrenia among first- and secondgeneration immigrants in the Netherlands’
• Veling, W.A. (2008)