Biological explanations for schizophrenia

• Outline the researcher, sample, IV, DV and findings of the research into concordance rates of schizophrenia and genetic similarity?

  This research was carried out by Grottesman in 1991. The sample consisted of 2.7 million danish people, with 196 schizophrenic couples and 270 of their children. The IV was whether the parents has schizophrenia. The DV was the diagnosis of schizophrenia in their children. He found that the general populations probability was 1%. It was 17% if they had a diagnosed fraternal twin and 48% for an identical twin. The probability if your parents are diagnosed is at 6%.
• What are candidate genes?

  A candidate gene for schizophrenia, for example, would be a proven gene that increases the likelihood of an individual developing schizophrenia.
• What does polygenic mean?

  Refers to a conditions that has multiple candidate genes.
• Outline Ripke et al's study

  Combined all genome-wide studies of schizophrenia. The genetic make-up of 37,000 was compared to a control of 113,000. Found 108 genetic variations that were associated with a higher risk of schizophrenia.
• What does it mean for Schizophrenia to be aetiologically heterogenous?

  Multiple factors contribute to the development of schizophrenia, including genetic variation but also environmental/cognitive factors.
• How can mutation in parental DNA occur?

  Through viral infections, poison or radiation.
• Where does evidence of gene mutation in risk of schizophrenia come form?

  Brown et al (2002) found positive correlation between age (increased sperm mutation) and schizophrenia. ). 0.7% under 25 to over 2% in over 50's.
• What is a neural correlate?

  Patterns of structure and activity in the brain that occurs along side an experience, suggesting possible implication of said experience.
• What is the dopamine hypothesis?

  Dopamine is a neural correlate for schizophrenia. The idea that schizophrenia is cause by hyperdopaminergia (high levels of dopamine) in subcortical areas of the brain. For example, too much dopamine in broca's area could be responsible speech poverty/auditory hallucinations.
• Whats the updated dopamine hypothesis?

  The proposed addition of cortical hypodopaminergia (too little) dopamine levels. Low DA levels in PFC could explain cognitive (negative) symptoms. This can lead to subcortical hyperdopaminergia so both high and low levels of DA present. Also tries to explain this onset of abnormal DA with genetics and stress (psychological and physical).
• AO3 research support (genes)

  Genetics have strong evidence base. Tienari et al shows that biological children with schizophrenic parents are at heightened risk (even adopted). Hilker et al - concordance of 33% for MZ and 7% for DZ. Shows vulnerability due to genetic make-up. Provides credibility to the explanation, more likely to be accurate and reliable.
• AO3 nature/nature.

  Gottesman's study is a meta-analysis of family studies. Suggests this provides a basis of a genetic cause. However, it ignores the impact someone's environment. Family studies could easily be argued for nurture side because they share similar environments along with genetics. This suggest a confounding variable such as environmental familiarity is measured over the believed genetics. Reduces the validity of Grottesman's study.
• AO3 Evidence for dopamine

  Support for the idea that dopamine is involved in schizophrenia. Firstly, antipsychotics reduce DA levels to reduce symptoms. Also amphetamines increase DA which worsens symptoms. Suggests dopamine is involved is the symptoms for schizophrenia. Provides credibility to the explanation, more likely to be accurate and reliable.
• AO3 Reductionist

  Only focuses on the role of one neurotransmitter (DA). However there is evidence to suggest glutamate affects symptoms fo schizophrenia as well. Post-mortum and live scannings showing increased glutamate levels. Also some candidate genes are related to glutamate. Therefore an equally strong case can be argued for other neurotransmitters other than DA. Reductionist, dopamine hypothesis ignores importance of other schizophrenia affecting neurotransmitters.