Explanations of Schizophrenia

Genetic - Gottesman & Shields, 1972  Carried out a twin study which looked into the genetic inheritance of schizophrenia. This explanation believes that mental disorders such as schizophrenia can be explained by genes or particular combinations of genes that are passed on to offspring. Schizophrenia patients has sensory dysfunction such as psychosis, which has genetic origins. The study uses identical or monozygotic (MZ) twins who share all their DNA, whereas non-identical or dizygotic DZ) twins only share around 50% of their DNA. This is helpful because of the the disorder is the same in both identical and non-identical twins then it can be concluded that there is probably little genetic connection as in theory the more of the same DNA the more likely it would be for them to both have schizophrenia rather than just one. Twins allow the detailed study of nature vs nurture debate. The sample of this study was 467 twins that were registered at the Maudsley psychiatric hospital in London. They selected 57 pairs of twins 24 MZ and 33 DZ twins (they were identified as MZ or DZ by blood tests and finger print tests. The researchers interviewed the patient and their twin (some of the patients already had a diagnosis of schizophrenia). Participants also took part in cognitive tests such as object sorting. To make sure the diagnosis was valid case studies of each participants were independently evaluated by judges not involved in the research. This study found that around 50% of MZ twins shared schizophrenia, it was found to be much lower in DZ twins (9%) It was also found that severe cases were much likely to share the disorder with their their twin, less severe cases were way less likely to share it with their twin.    Strengths- Used a large sample of MZ and DZ twins, the independent judges that were used to assess cases reduced researcher bias greatly, they also collected data via qualitative methods such as interviews. Weaknesses- The information isn't very representative of people without twins the sample was drawn from one hospital only making it less generalisable, the interviews and qualitative data they use could be considered subjective and open to bias.  

Biochemical Dopamine Hypothesis- Lindröm 1999 This hypothesis states that brain of one with schizophrenia produces more dopamine than those without the disorder. Dopamine is a neurotransmitter meaning it is a chemical substance which enables communication between two neurons. In order for a nerve impulse to travel across cells in has to move across a small junction know as the synapse. This hypothesis identifies a link between excessive amounts of dopamine or dopamine receptors and schizophrenia positive symptoms. Its thought that an excessive amount of dopamine in certain parts of the brain can be related to certain symptoms. Some drugs such as cocaine and amphetamines increase levels of dopamine, the results of these drugs can sometime be confused with schizophrenia symptoms. Autopsies have been done on brains of a schizophrenic, it was found that they had more dopamine receptors. Another study by Wise et al 1974 found the. brain fluid from patients had abnormally low levels the enzyme that breaks down dopamine.  Positron emission tomography is sometimes used to see where dopamine activity is highest in the brain, certain areas link to certain symptoms. Lindroms study tests patients with Parkinson disease who are often treated with a synthetic dopamine called L-dopa, If their dosage is too high they exhibit identical symptoms of schizophrenia.   Strengths- This explanation has a lot of background studies backing it up such as Wise and Lindrom, strong evidence such as the brain fluid and the Parkinson disease show truth to this theory  Weaknesses- Its uncertain if to much dopamine is produced, too many receptors are present or both.

Cognitive - Frith 1992  This approach recognises that the biological factors contribute in some way to the positive symptoms of schizophrenia. Frith accepts the biological role however he incorporates the idea of faulty though processes as well. For example someone with "voice" in their head could simply be misinterpreting their own thoughts. Frith tested this idea with schizophrenic patients by asking them to decide whether items that had been read out loud were done so by themselves an experimenter or a computer. People with incoherent speech performed worst at the task which could be linked to memory and attention difficulties used in self monitoring. Frith also believed that the positive symptom delusional thinking may a be a misintreprtation of perception. The misinterpretations can lead to delusions paranoia and incoherence. He also believed that negative symptoms were due to a lack of theory of mind which create problems in recognising intentions of other which leads to paranoid thinking. Strengths- It recognises the biological side and adds on to it  Weaknesses- It requires a very open mind