Evaluation of the dopamine hypothesis

How can we evidence the legitimacy of version 1?

Drugs that increase dopamine have shown to create hallucinations e.g amphetamine and the drug L-Dopa used to treat people with Parkinson’s disease who have low levels of dopamine showing that too much dopamine can result in schizophrenic symptoms

What is scientific evidence that supports the use of drugs?

Randrup and Munkuad (1966) gave amphetamines to rats and showed behaviours similar to schizophrenia (catatonia, withdrawals) and symptoms dissapeared when given a neuroleptic to inhibit dopamine activity

How are PET scans used?

Patel (2010) used PET scans and found lower levels of dopamine in prefrontal cortex compared to control group which result in negative symptoms, prefrontal hypodopaminergia

What type of scientific studies are used in each version of the dopamine hypothesis?

Version 1 - Drug studies e.g L-Dopa, Amphetamines. Parkinson’s disease

Version 2 - Animal studies e.g Randrup & Munkuad (1966)

Version 3 - PET scans e.g Howes, Patel (2010)

What are the weaknesses with the scientifics behind dopamine hypothesis?

Evidence is correlational so it is hard to determine cause and effect between schizophrenia and dopamine activity, Research using PET scans still haven’t been able to detect differences between dopamine in SCZ and non SCZ

Why can PET scans be inaccurate and which version does this effect?

PET scans are useful to explain version 3 because they show a live reaction in dopamine with risk factors such as stress and drug use. However these provide estimates on dopamine levels based on models which are prone to errors

What is the strength of determinism?

Reduces stigma by saying there is a biological affect (prefrontal hypodopaminergia & striatal hyperdopaminergia) and not a choice by free will.

What evidence supports determinism?

Randrup and Munkuad animal studies showed rats displayed schizophrenic symptoms, Davis 1991 version 2 suggests dopaminergic level imbalances cause symptoms which takes away blame.

What are the weaknesses of determism?

The dopamine hypothesis is still biologically deterministic suggesting that the only treatment would be biological however we know that CBT can help schizophrenics. Version 3 also suggests that some environmental factors can be to blame such as drug use or stress.

What is the strength of reductionism?

Reduces schizophrenia to dopamine imbalance, allowing for more scientific testing and treatment. The biological reductionism has allowed for treatments to be aimed at biological processes such as chlorpromazine which has been highly effective in treating schizophrenic symptoms.

What are the weaknesses behind reductionism?

Reduces the only cause as being dopamine whereas there are many other biological and environmental factors that come into play. The drug Clozapine focuses on D2 receptors but also serotonin

What evidence suggests that schizophrenia isn’t just dopamine imbalance?

Moghaddam and Javitt (2012) found schizophrenics have a deficiency in glutamate function

What did Howes and Kapur (2009) say about the dopamine hypothesis reductionism?

They acknowledged the possibility that dopamine as the final common pathway may be demolished and replaced by a new system that shows no interaction with dopamine