Biological Explanation to Schizophrenia
Ø Has much support
Ø Doesn’t rule out psychological factors
Ø Current thinking is – ‘diathesis-stress’ relationship.
Ø Diathesis-stress relationship = there are biological predispositions (the diathesis) for Schizophrenia THAT only develops into the disorder if significant psychological stressors (stress) are present. (Gottesman and Riley), 2003
4 different explanations:
Ø Genetic factors
Ø Biochemical Factors
Ø Brain dysfunction/neuroanatomy
Ø Viral Infection
Biological relatives – Gottesman 1991 and Kendler 1995 found Schizophrenia is more common in the biological relatives of a schizophrenic.
The closer the degree of relatedness the greater risk
Twin studies compare the concordance rates for:
• identical or MZ twins (identical genes, same environment)
• and fraternal or DZ twins (same environment but not identical genes).
• Identical twins:
• Research has consistently shown identical twins have a higher risk of developing schizophrenia if the other twin has it. Gottesman & Shields 1982 – 58%), Gottesman meta-analysis 1991 – 48%
• Why is this? – Because identical twins share 100% genes.
• Fraternal twins:
• Only have a 17% chance
• Why – because they share only 50% same genes (Janicak at al 2001).
Ø Kety et al 1988 found 14% of biological relatives of adoptees with schizophrenia were classified as schizophrenic, whereas only 2.7% of their adoptive relatives were found to be.
Ø Insights from molecular biology
Ø Miyakawa et al (2003) – created genetically modified ‘schizophrenic mouse’ by switching off a specific gene in the brain responsible for making the chemical calcinerurin.
Ø Mice showed abnormalities e.g. social withdrawal mirrored behaviour of schizophrenic patients.
Ø Miyakawa et al (2003) studied DNA families with schizophrenia, found those who had it were more likely to have defective version of the gene.
The dopamine hypothesis