Schizophrenia
Characteristics
- Alogia - poverty of speech, a reduction in the amount of speech but
also a lack of meaning to speech (negative)
- Flatness of affect – individuals appear to have no emotions, they show
little or no facial expression – can be interpreted as apathetic, speech
is very monotonous (negative)
- Catatonic behaviour – this can range from vast, repetitive movement to
no movement at all e.g. wandering round in circles (negative)
- Avolition – individual seems unconcerned with what is going on around
them due to loss of interest and motivation, they show no will or desire
to take part in activities (negative)
- Anhedonia – an individual does not react appropriately to pleasurable
experiences, e.g. a football fan may not demonstrate any pleasure to
their team winning (negative)
- Disorder thinking – the person’s thoughts seem to jump from one topic
to another for no apparent reason and with no logical flow, speech may
be muddled and very hard to follow – ‘word salad’ (positive)
- Hallucinations – these are perceptions that are not real, can be visual,
auditory or tactile (positive)
- Delusions – beliefs that aren’t real, they are usually experienced with
no evidence to support the belief (positive)
Biological explanations
- Dopamine hypothesis
o Initial dopamine hypothesis
The initial dopamine hypothesis proposed that individuals
with schizophrenia had too much dopamine, therefore they
demonstrated symptoms related to high levels of
dopamine
Griffith et al (1968)
Proposed those with schizophrenia have too much
dopamine
Induced psychosis in non-schizophrenic volunteers
using dextro-amphetamine (a drug that increases
levels of dopamine)
Participants quickly developed paranoid delusions as
well as a cold and detached emotional response
Issues with this hypothesis
, Was too simplistic
When drugs were given to reduce dopamine levels,
they reduced positive symptoms but had little to no
effect on negative symptoms
o Revised dopamine hypothesis
Research has shown the impact of antipsychotic drugs on D2 dopamine
receptors which are primarily found in the limbic system. Therefore,
the role of dopamine in the limbic system has been the main area of
study in more recent years.
Main functions of the limbic system
Processing emotions, memory formation and arousal
Nerve pathways leave from the limbic system to many other structures in
the brain. Two of the main pathways associated with schizophrenia
include the mesolimbic and mesocortical pathway
Mesolimbic pathway
Carries signals from the ventral tegmental area to nucleus
accumbens. Too much dopamine causes overstimulation and
ultimately positive symptoms
Mesocortical pathway (Davis et al (1991))
Carries signals from the ventral tegmental area to the frontal lobe
– this verve pathway is vital in emotional responses, memory and
cognition
Davis et al (1991) noted that too little dopamine is
evident in D1 receptors of the frontal lobe of many
individuals with the negative symptoms of
schizophrenia
- Evaluation
o Supporting evidence: Griffith et al (1968)
This research supports the dopamine hypothesis and the
concept that increased dopamine levels are linked to
psychotic symptoms
Evaluation:
The use of volunteers (non-schizophrenics) reveals
very little about actual sufferers and suggests that
we should question the usefulness of this research
o Methodological issues
Difficult to make direct measurements of neurotransmitters
like dopamine as it involves an unpleasant procedure
(lumbar puncture) to measure HVA levels
, Levels of measurements may be seriously affected by
participant’s diet and drug use as it affects metabolite
levels, even when research is conducted under controlled
conditions, the results can be difficult to interpret with HVA
levels varying widely between participants
We need to have refined procedures for measuring
neurotransmitters
Dopamine is metabolised into homovallinic acid which is
found in cerebrospinal fluid
o Incomplete explanation
Dopamine is not the only neurotransmitter implicated in
schizophrenia. Serotonin has also been identified as a
potential influence.
Newer antipsychotic drugs that block the D2 receptor and
the 5-HT2A serotonin receptor have been found to be more
effective at treating psychotic symptoms than traditional
antipsychotics that only target dopamine imbalances.
This suggests that the dopamine hypothesis only offers a
partial explanation for schizophrenia.
o Application to methods of modification
For the too much dopamine explanation
Conventional antipsychotics
o Phenothiazine – earliest type (1950s – before
this scz was seen as untreatable) of
antipsychotic drug and it revolutionised
psychiatry
It sedates the person and reduces
symptoms of schizophrenia e.g.
hallucinations and delusions by binding
to dopamine receptors and blocking the
build-up of dopamine
Cole et al (1964) - 75% given this drug
were seen to have improved compared to
25% who were given placebo – 48% of
those given the placebos were
considered to have gotten worse
compared to none in phenothiazine
condition
- Genetics
o Family studies
Characteristics
- Alogia - poverty of speech, a reduction in the amount of speech but
also a lack of meaning to speech (negative)
- Flatness of affect – individuals appear to have no emotions, they show
little or no facial expression – can be interpreted as apathetic, speech
is very monotonous (negative)
- Catatonic behaviour – this can range from vast, repetitive movement to
no movement at all e.g. wandering round in circles (negative)
- Avolition – individual seems unconcerned with what is going on around
them due to loss of interest and motivation, they show no will or desire
to take part in activities (negative)
- Anhedonia – an individual does not react appropriately to pleasurable
experiences, e.g. a football fan may not demonstrate any pleasure to
their team winning (negative)
- Disorder thinking – the person’s thoughts seem to jump from one topic
to another for no apparent reason and with no logical flow, speech may
be muddled and very hard to follow – ‘word salad’ (positive)
- Hallucinations – these are perceptions that are not real, can be visual,
auditory or tactile (positive)
- Delusions – beliefs that aren’t real, they are usually experienced with
no evidence to support the belief (positive)
Biological explanations
- Dopamine hypothesis
o Initial dopamine hypothesis
The initial dopamine hypothesis proposed that individuals
with schizophrenia had too much dopamine, therefore they
demonstrated symptoms related to high levels of
dopamine
Griffith et al (1968)
Proposed those with schizophrenia have too much
dopamine
Induced psychosis in non-schizophrenic volunteers
using dextro-amphetamine (a drug that increases
levels of dopamine)
Participants quickly developed paranoid delusions as
well as a cold and detached emotional response
Issues with this hypothesis
, Was too simplistic
When drugs were given to reduce dopamine levels,
they reduced positive symptoms but had little to no
effect on negative symptoms
o Revised dopamine hypothesis
Research has shown the impact of antipsychotic drugs on D2 dopamine
receptors which are primarily found in the limbic system. Therefore,
the role of dopamine in the limbic system has been the main area of
study in more recent years.
Main functions of the limbic system
Processing emotions, memory formation and arousal
Nerve pathways leave from the limbic system to many other structures in
the brain. Two of the main pathways associated with schizophrenia
include the mesolimbic and mesocortical pathway
Mesolimbic pathway
Carries signals from the ventral tegmental area to nucleus
accumbens. Too much dopamine causes overstimulation and
ultimately positive symptoms
Mesocortical pathway (Davis et al (1991))
Carries signals from the ventral tegmental area to the frontal lobe
– this verve pathway is vital in emotional responses, memory and
cognition
Davis et al (1991) noted that too little dopamine is
evident in D1 receptors of the frontal lobe of many
individuals with the negative symptoms of
schizophrenia
- Evaluation
o Supporting evidence: Griffith et al (1968)
This research supports the dopamine hypothesis and the
concept that increased dopamine levels are linked to
psychotic symptoms
Evaluation:
The use of volunteers (non-schizophrenics) reveals
very little about actual sufferers and suggests that
we should question the usefulness of this research
o Methodological issues
Difficult to make direct measurements of neurotransmitters
like dopamine as it involves an unpleasant procedure
(lumbar puncture) to measure HVA levels
, Levels of measurements may be seriously affected by
participant’s diet and drug use as it affects metabolite
levels, even when research is conducted under controlled
conditions, the results can be difficult to interpret with HVA
levels varying widely between participants
We need to have refined procedures for measuring
neurotransmitters
Dopamine is metabolised into homovallinic acid which is
found in cerebrospinal fluid
o Incomplete explanation
Dopamine is not the only neurotransmitter implicated in
schizophrenia. Serotonin has also been identified as a
potential influence.
Newer antipsychotic drugs that block the D2 receptor and
the 5-HT2A serotonin receptor have been found to be more
effective at treating psychotic symptoms than traditional
antipsychotics that only target dopamine imbalances.
This suggests that the dopamine hypothesis only offers a
partial explanation for schizophrenia.
o Application to methods of modification
For the too much dopamine explanation
Conventional antipsychotics
o Phenothiazine – earliest type (1950s – before
this scz was seen as untreatable) of
antipsychotic drug and it revolutionised
psychiatry
It sedates the person and reduces
symptoms of schizophrenia e.g.
hallucinations and delusions by binding
to dopamine receptors and blocking the
build-up of dopamine
Cole et al (1964) - 75% given this drug
were seen to have improved compared to
25% who were given placebo – 48% of
those given the placebos were
considered to have gotten worse
compared to none in phenothiazine
condition
- Genetics
o Family studies
