The Dopamine Hypothesis - Biological Explanations of Schizophrenia

Question 1

What is the dopamine hypothesis?

Answer 1

• Dopamine is a neurotransmitter which is associated with pleasurable
  sensations, along with learning, memory, motor system function.
• The original version of the dopamine hypothesis focused on the possible role of high levels of dopamine known as, hyperdopaminergia in the central areas of the brain leads to the symptoms of schizophrenia
• A second explanation suggests that it is not excessive dopamine but the fact that there are more dopamine receptors and low levels of dopamine (hypodopaminergic). - -More receptors lead
  to more firing and an overproduction of messages.

-It may be that both hyper and hypodopaminergia are correct explanations - both high and low levels of dopamine in different brain regions are involved in schizophrenia.

Question 2

A03 - Amphetamine Research

Answer 2

• Evidence to support the role of dopamine in the onset of sz comes from the fact that amphetamines increase the amounts of dopamine.
• Large doses of amphetamine given to
  people with no history of psychological disorders produce behaviour which is very similar to
  paranoid schizophrenia.
• Small doses given to people already suffering from schizophrenia
  tend to worsen their symptoms.

-However, this is not the case for all individuals suggesting that the dopamine hypothesis may not be a fully comprehensive explanation for all cases of
schizophrenia.

Question 3

A03 - Medication Research - Noll

Answer 3

• It has been found that antipsychotic medication that targets dopamine levels is effective in
  approximately 60% of patients, providing some support for the dopamine hypothesis.
• However, Noll (2009) argues that antipsychotic drugs do not alleviate hallucinations and
  delusions in about one-third of patients.
  -Noll also points out that, in some people, hallucinations and delusions are present despite levels of dopamine being normal.
  -Blocking the D2 receptors of these individuals has little or no effect on their symptoms.

-Whilst typical drugs have addressed the dopamine levels, atypical recent drugs address serotonin, glutamate and dopamine levels.

• This suggests that, rather than dopamine being the sole cause of positive symptoms, other neurotransmitters may be implicated such as glutamate and serotonin, thus questioning the hypothesis.

Question 4

A03 - Reductionist

Answer 4

-The dopamine hypotheses are highly reductionist as it reduces the complex symptoms of
schizophrenia to a relatively simple level of explanation, e.g. that of dopamine dysfunction.

• It is unlikely that dopamine dysfunction works in isolation.
  -For instance, there is compelling evidence to show that, when dopamine levels of an individual are reduced, other substances
  e.g. insulin and glucose respond and compensate for abnormal levels of dopamine.
• Hence, whilst contributing to a wider comprehensive explanation, these dopamine hypotheses
  remain reductionist.