Schizophrenia: Contemporary Study (Carlsson et al 1999) Flashcards
(15 cards)
What were the aims of this contemporary study?
- To review studies into the relationship between dopamine and glutamate on the symptoms of schizophrenia
- To explore glutamatergic deficiency which is a rival theory of the dopamine hypothesis
- to provide more of an explanation for sz than simply the dopamine hypothesis
- to review anti-psychotic drugs that could be more effective with fewer side effects.
Define ‘glutamate’.
A neurotransmitter nerve cells use to send messages to other nerve cells that controls memory and learning. It is the brains main excitatory neurotransmitter.
What was used in the sample?
32 studies investigating neurochemical levels in patients with schizophrenia.
33 in total, 1 was unpublished (not peer reviewed)
What type of method was used?
Literature review
Briefly describe the procedure of this contemporary study.
- used secondary data.
- Reviewed 32/33 pieces of research into the relationship between neurotransmitters and schizophrenia
- 14 studies were conducted by himself
- variety of studies were used e.g. some investigating neurochemical levels in patients with sz, as well as studies into drugs known to induce symptoms of psychosis, such as PCP (angel dust)
- some research on rodents was used to test NT functioning and related brain structure. Evidence also came from studies looking at mice.
- Considered evidence from studies on the use of recreational drugs known to induce psychosis and studies into the effectiveness of drugs used to treat schizophrenia and their method of action on the brain
- specific evidence comes from Hietala et al (1994) who found there is greater amphetamine induced release of dopamine in the basal ganglia in those with sz as seen in SPECT and PET scans, as well as from Lindstroem et al….
- Carlssons own research included the (1989) animal study about the use of MK-801 drug to change rodent behaviour.
What were the 3 parts to the results of Carlsson’s study?
- dopamine and glutamate
- thalamic filter
- drug treatments.
Briefly describe the first part of the results.
- found that excess dopamine is likely to be too simplistic.
- found that PCP (angel dust) leads to psychosis and blocks glutamate receptors (specifically NMDA) so perhaps glutamate deficiency has a role in psychosis.
- thought that low glutamate leads negative symptoms such as cognitive disturbances.
- glutamate failure in cerebral cortex leads to pos symptoms, glutamate failure in the basal ganglia can lead to positive symptoms
- REDUCED levels of glutamate are associated with INCREASED dopamine release- so THE TWO INTERACT
- dopamine neurons are controlled by glutamatergic neurons- acting either as breaks or accelerators.
Briefly describe the second part of the results.
Thalamic filter
* this pathway is involved in sz
* indirect pathway- too much dopamine and too little glutamate- this will create overload, resulting in POSITIVE symptoms.
* direct pathway- excitatory, so abnormal evils of glutamate and dopamine reduce the excitation of the thalamus, thus reducing activity in the c.c, creating NEGATIVE symptoms.
Briefly describe the third part of the results.
Drug treatments
* research has shown that clozapine is a highly effective drug treatment for sz.
* clozapine has both antidopamergic and serontonergic properties.
* it is highly effective in patients that haven’t previously responded to treatment.
* due to relationship between serotonin and glutamate, we could infer that difficulty in treating sz patients may belong to a subgroup whose disorder may be better explained by reduced levels of glutamate.
* proposed reciprocal inhibition between serotonin and glutamate in the PFC (I.e. if serotonin is inhibited then so is glutamate).
* clozapine increases serotonin activity- so also increases glutamate activity = reduction in symptoms.
Describe the conclusion of this contemporary study.
- Carlsson concluded that further research is needed in developing drugs to treat schizophrenia that avoid negative side effects
- This should be done by considering more neurotransmitters than dopamine in the development of the disorder
- Schizophrenia may have different types that could be caused by different neurotransmitters
Evaluate the generalisablity using a high and low point.
A strength is the high levels of generalisability. This is because Carlson used 32 pieces of research looking at the different types of schizophrenia, including….Therefore this represents all/most patients with schizophrenia, so results can be generalised to a wider schizophrenic society.
A weakness is the low generalisability-used animal research. Humans have much more complex brain structures etc so results can’t be generalised.
Evaluate the reliability using 2 high points.
A strength is that there is high levels of reliability. This is because the secondary data in the literature review used reliable methods such as PET scans and lab experiments. These are objective and can be easily replicated to test for consistency, easily comparable.
A strength is the high levels of reliability. The large range of research and findings support each other- the 32 different studies used all agree etc, so more reliable conclusions.
Are there any applications?
A strength is that there are positive applications to society. Carson showed that there are potentially more neurotransmitters such as serotonin and glutamate involved in the development of schizophrenia. Therefore drugs can be developed to tackle different types and different symptoms, including negative ones, leading to the development of second generation antipsychotics such as clozapine. This treatment ent method is more effective for sz which is beneficial for patients whose current medications are ineffective due to targeting solely dopamine, which may not be the cause of their sz.
Evaluate the validity using a high and low point.
A weakness is the low levels of temporal validity. This is because research which Carlsson used was included the 1989 study he conducted on animals about the use of MK 801 to change rodent behaviour, and the 1999 study Lindstroem et al conducted used radioactively labelled L-DOPA. These studies used techniques which are less advanced than today’s neuroimaging or genetic tools. This reduces the studies temporal validity, as more recent methods provide updated insights into sz that were not available then such as genetic analysis.
A strength is the triangulation of data. Carlsson reviewed a range of 32 studies using different methods such as….to explore the neurochemical explanations of schizophrenia. By seeing similar results of…. Across findings,it reduces the chance that his findings are due to researcher bias and methodological flaws, increasing the internal validity of findings.
A weakness is that there is low internal validity. This is because Carlsson used secondary data, of which only 14 were his own studies. This means that they have been made for a purpose other than Carlssons aim of reviewing the relationship between dopamine and glutamate on the symptoms of sz. This means that as the data was already in existence, there is no control over the methodology or if there was any confounding variables in the data collection. This reduces the credibility and the accuracy of conclusions etc.
A strength is the high levels of validity- lab experiments are highly scientific with strict controls over extraneous variables, increasing the validity of findings.
Evaluate the ethics using 2 high points.
A strength is that only secondary data was used. 32 studies were used which were in the public domain and so therefore no ethical considerations were to be made, and no ethical guidelines were broken. Additionally, the purpose of carlssons research was to improve treatment for those with sz, and so this has an ethical purpose.
