1. Schizophrenia

2. Problems with diagnosing A true diagnosis cannot be made until a patient is clinically interviewed. Psychiatrists are relying on retrospective data, given by a person whose ability to recall much relevant information is unpredictable. Some may be exaggerating the truth – or blatantly lying!

3. Problems with diagnosing Beck et al (1961) looked at the inter-rater reliability between 2 psychiatrists when considering the cases of 154 patients. The reliability was only 54% - meaning they only agreed on a diagnoses for 54% of the 154 patients! It was originally hoped that the use of diagnostic tools could provide a standardised method of recognising mental disorders. However clear the diagnostic tool, the behaviour of an individual is always open to some interpretation. The process is subjective.

4. Explanations – Biological vs. Psychological Nature vs. Nurture

5. Biological explanations: pages 164-165 The biological approach is also known as the ‘medical model’ This approach sees mental disorders as having physical causes A number of biological explanations for schizophrenia have emerged

6. Biological Explanations Genetics Biochemicals Brain Structure

7. Genetics – Twin Studies Twin studies help researchers to work out whether its nature or nuture influences Gottesman (1991) suggests that schizophrenia is inherited through genes. Studied 40 twins - the concordance rate for MZ twins is about 48% and only about 17% for DZ twins. Also Joseph (2004) – showed concordance rate of 40.4% MZ and 7.4% for DZ.

8. Evaluation – Twin Studies Twin studies seem to indicate that there is a strong genetic component to the disorder The fact that the concordance rate for twins is not 100% means that schizophrenia cannot be accounted for by genetics alone The higher concordance between MZ twins could be explained by greater environmental similarity rather than genetic similarity – MZ twins elicit more similar treatment than DZ twins (so can be explained by other theories) Sample sizes of such twin studies is always going to be very small

9. Twins - evaluation Twin studies demonstrate that there may be a predisposition to develop schizophrenia, however, the fact that both twins do not always develop schizophrenia means that environmental factors must also play a part No single gene has been identified for schizophrenia, questioning genetics as a valid explanation for schizophrenia. Evidence for concordance rates for schizophrenia are based on older twin studies which are less reliable due to changes in the diagnostic criteria. These days, diagnosis is much rigorous than it was 40 years ago so some of those diagnosed as schizophrenic 40 years ago might not meet the criteria now

10. Genetics - Adoption Studies These are studies of genetically related individuals who have been reared apart due to being adopted. Tienari (2000), found that of the 164 adoptees whose biological mothers had been diagnosed with schizophrenia, 6.7% also received a diagnosis of schizophrenia, compared to just 2% of the 197 control adoptees Although only a small percentage, it still suggests that genes must play a role within schizophrenia. Tienari conducted his study within Finland, therefore we are not able to generalise this study to the rest of the world

11. Genetics – Family Studies Gottesman also studied families – he concluded that if both parents suffer from schizophrenia, then there is a 46% chance of also developing the disorder (compared to a 1% chance for the general population). Findings have shown that the greater the degree of genetic relatedness, the greater the risk of developing schizophrenia.

12. Genetics – Family studies This shows that genes do play an important factor, however if genes were the only cause of schizophrenia then the percentages surely should be 100%, The theory could be seen as deterministic; just because we are ‘predisposed’ by our genes cannot mean we necessarily get the disorder schizophrenia. Many researchers now accept that schizophrenia concordance rates in families may be more to do with common rearing patterns or other environmental factors that have nothing to do with heredity.

13. Biochemical Factors – The Dopamine Hypothesis Dopamine is a neurotransmitter Dopamine neurons are instrumental in regulating attention, therefore if this process is disturbed it may lead to problems with attention, perception and thought – characteristics of schizophrenia This theory claims that excessive amounts of dopamine or an oversensitivity of the brain to dopamine is the cause of schizophrenia. The dopamine hypothesis states that messages from neurons that transmit dopamine fire too easily or too often, leading to the characteristic symptoms of schizophrenia. Schizophrenics are thought to have abnormally high numbers of D2 receptors on receiving neurons, resulting in more dopamine binding and therefore more neurons firing

14. Biochemical – Dopamine hypothesis Evidence for dopamine includes:  Amphetamines; this is a dopamine agonist, this stimulates nerve cells containing dopamine causing the synapse to be ‘flooded’ – due to large doses of the drug can cause hallucinations and delusions of a schizophrenic episode.  Cocaine also increases the levels of dopamine in the brain and can cause the positive symptoms of schizophrenia and exaggerate them in people who already have the disorder.  Antipsychotic drugs (dopamine antagonists) which block the activity of dopamine in the brain, by reducing the stimulation of the dopamine system, eliminates hallucinations and delusions. By alleviating many of the symptoms of schizophrenia, antipsychotic drugs strengthen the case for dopamine being a significant contributory factor.  L-Dopa – a drug for Parkinson’s disease actually increases dopamine – this in turn can produce symptoms of schizophrenia. An agonist is a chemical that binds to a receptor of a cell and triggers a response by that cell. An antagonist blocks or reduces the effect of a neurotransmitter

15. Neurochemical – Dopamine hypothesis: Evaluation Post mortems have revealed higher then normal levels of D2 dopamine receptors in the brains of schizophrenics PET scan of schizophrenics have found similar results However, you can’t establish cause and effect The dopamine hypothesis is over simplistic as there are lots of neurotransmitters involved, not just dopamine.

16. Neuroanatomy - Brain Structure There is growing evidence that schizophrenia is down to structural abnormalities in the brain – brain scanning techniques have made it possible to investigate living brain images. There are, however issues of causality Young et al found that the degree of abnormality correlated with the severity of the symptoms.

17. Brain Structure People with schizophrenia have abnormally large ventricles in the brain. Ventricles are fluid filled cavities. This means that the brains of schizophrenics are lighter than normal.

19. Physiological abnormalities - evaluation Findings are inconsistent Cause and effect can not be established with brain abnormalities - it is still uncertain whether structural abnormalities predispose to schizophrenia, or whether the onset of the clinical symptoms causes structural changes. Enlarged ventricles may be the result of taking anti-psychotic medication Fails to take into account environmental factors It is deterministic It is over simplistic

20. Summary Biological explanations do account for schizophrenia, however the fact that there is no conclusive explanation that accounts for all schizophrenics Psychological explanations need to be considered also. A ‘diathesis-stress’ relationship may be at work – an individual may have a genetic predisposition for schizophrenia but it may be due to environmental factors that lead to the onset of the condition

21. Essay title: Describe and evaluate one or more biological explanation for schizophrenia. In your evaluation you should refer to research evidence. (8 marks + 16 marks)