Biological Explanations Flashcards
(31 cards)
How do biological explanations explain schizophrenic symptoms?
explain schizophrenic symptoms in terms of physiological symptoms e.g neurotransmitters, neuroanatomy, genetics and hormones.
What are the two biological explanations of schizophrenia?
The Role of Dopamine
The Role of Genetics
When was the original Dopamine Hypothesis first proposed?
in 1967 by Van Rossum
What causes positive symptoms? in the original Dopamine Hypothesis
Too much dopamine in the subcortical and limbic regions of the brain
What causes negative symptoms? in the original Dopamine Hypothesis
Less dopamine in the prefrontal cortex
What is Dopamine?
a neurotransmitter (a chemical messenger) that helps send signals between neurons. It is released between specific brain circuits and directly responsible for motivation and reward, impacts motor control and cognitive functions.
Where was the link of dopamine and schizophrenia developed from?
Research into parkinsons disease
-Individuals with Parkinsons disease suffer with low levels of dopamine and L-Dopa (a percursor to dopamine) was given to raise dopamine in the brain and some individuals went on to develop schizophrenia like symptoms.
What early research resulted in individuals developing positive symptoms of schizophrenia.
Griffith et al 1968
induced psychosis in a group of non-schizophrenic voluntees and were given a drug to raise levels of dopamine (dextro-amphetamine)
-resulted in paranoid delusions and cold emotional response
What did Griffith et al find when administering a drug that reduced levels of dopamine?
-not very effective
-view of dopamine is too simplistic
What is now thought of the dopamine levels of schizophrenics
They have an abnormally high number of dopamine receptors especially the D2 receptors (found in subcortical regions of the limbic system.) Neuron that use the neurotransmitter dopamine fire too often so transmit too many messages.
What functions has research found that these receptors are associated with?
-emotions
-memory formation
-arousal
What is schizophrenia viewed as?
a complex entity with four doperminergic pathways in the brain involved
Name the 4 dopaminergic pathways
- Mesolimbic
- Mesocortical
- Nigrostriatal
- Tuberoinfundibular
Mesolimbic Pathway
positive symptoms such as hallucinations and delusions are linked with too much dopamine in the mesolimbic pathway causing overstimulation.
Mesocortical Pathway
negative symptoms of schizophrenia e.g flat affect are linked with too little dopamine in the mesocortical pathway causing cognitive impairments.
Nigrostriatal Pathway
dopamine produced here triggers physical movements includes the parts of the face and mouth needed for speech. Problems with this may be responsible for some symptoms of schizophrenia alogia (lack of speech) and psychomotor disturbances (catatonic movements)
Tuberoinfundibular Pathway
associated with mood changes
Supporting evidence of the role of dopamine
-Post mortems of the brain of schizophrenics have supported that there are generally large number of dopamine receptors and an increase in the amount of dopamine in the left amygdala (Owen et al 1987)
-Since the 2000s several PET studies have confirmed the link between changes in the dopaminergic activity and schizophrenic symptoms.
Alternative Evidence for the role of dopamine
-schizophrenia better understood under social psychological influences
-Linszen et al 1997 has shown the impact of family environment can have on relapse rates. Found a patient returning to a family with high expressed emotion is approx. x4 more likely to relapse than a patient whose family is low expressed emotion.
-Copolov and Crook (200) found no evidence of altered dopamine activity in schizophrenic’s brain
Usefulness for the role of dopamine
-effective in drug treatments such as antipsychotics
–Meltzer 2012 found that clozapine is effective in 30-50% of cases of schizophrenia when other drugs have failed
-schizophrenia viewed as untreatable before APS
-reduces hallucinations and delusions by blocking the build up of dopamine
-improves quality of life for sufferers
Nature/Nurture for Role of Dopamine
Nature - cause of schizophrenia purely biological and result of complications lies in dopamine pathways.
e.g too much dopamine in mesolimbic pathway causes positive symptoms
-can be seen as reductionist as oversimplifies a complex mental illness and doesn’t take into account other factors e.g childhood experiences
Determinism for Role of Dopamine
deterministic approach to mental illness as it suggests mental health is determined by level of the neurotransmitter dopamine which we have no conscious control over.
-negative in the treatment of mental problems as there could be an over-emphasis on identifying biological treatments when a psychological treatment could be more appropriate
-individuals may feel they have no control over wellbeing and mental health impacting on recovery
-positively physiological determinism can help remove blame from individuals and family as it not a result of bad parenting or dysfunctional families.
What does the genetic explanation state schizophrenia is
a genetic illness meaning that a gene(s) for schizophrenia can be passed down from parents to children. It also predicts that like many other genetic illnesses, others are likely to as well.
What is the lifetime risk of schizophrenia in the general population?
1% anything above this must be due to factors other than chance
