Explanations of Schizophrenia Describe and evaluate both physiological and psychological explanations of Schizophrenia (25)

HzA HzA Clip on biological causes of schizophrenia

Schizophrenia & dopamine THEORY ONE The dopamine hypothesis: – Schizophrenia is caused by excessive DA activity. – This causes abnormal functioning of DA- dependent brain systems, resulting in schizophrenic symptoms – DA can increase or decrease brain activity depending on the system you’re looking at psychlotron.org.uk

Dopamine Hypothesis (Snyder, 1976) Schizophrenics (sz) have abnormally high levels of dopamine SZ have abnormally high numbers of D2 receptors more dopamine binding and more neurons firing

The dopamine hypothesis Sz symptoms can be treated with DA antagonists (e.g. chlorpromazine). These are effective in 60% of cases with more impact on positive symptoms. AO2 – Supports role of DA again, but what about 40% who don’t respond? – Lack of impact on negative symptoms hints at two separate syndromes psychlotron.org.uk

That the drugs used to treat Schizophrenia symptoms (neuroleptics) block dopamine synapses and the release of dopamine. Side effects of neuroleptic drugs are similar to the symptoms of PD (a condition associated with low levels of dopamine) and is improved with use of L-dopa (Grilly, 2002) Post mortem examinations have also shown abnormally high levels of DA in SZ Dopamine Hypothesis is based on evidence

DA is high in some patients but not others A new drug (Clozapine) is more effective in reducing schizophrenic symptoms, but blocks DA activity less THEORY 2: Revised Dopamine Hypothesis (Davis Et al. 1991)

Revised Dopamine Hypothesis (Davis Et al. 1991) DA high in mesolimbic dopamine system (associated with positive symptoms) HYPERdopaminergia DA is low in mesocortical dopamine system (associated with negative symptoms) HYPOdopaminergia

THEORY 3: Glutamate Hypothesis (Olney and Farber, 1995) It’s not dopamine that is the key, but it is implicated because of its roles in glutamate production. DA receptors inhibit glutamate release and glutamate may be more closely related to the root cause

Task: Please draw and explain the Dopamine Hypothesis What does the revised DA hypothesis suggest and what is the proof of this? What is the Glutamate Hypothesis?

Here are some evaluation points of the Biochemical explanation, how could you use this in your essay? Neurological differences may be a cause or an effect Could be genetic or arises from birth complications (nurture rather than nature) Harris (1995) found that some sz may have experienced brain damage from anoxia at birth Torrey (1996) suggests a viral cause that would explain that more SZ were born in late winter Neuroleptic drugs block DA fairly rapidly, yet they are slow to reduce the symptoms of SZ Healy (2000) suggests that drug companies have inappropriately promoted DA Hypothesis