Transcript The medical model

The medical model
Biochemical explanation
Put simply, this explanation is that our bodies have a balance of
chemicals – if there is an imbalance this could lead to a mental health
issue.
One big problem for this is that it is difficult to establish cause and
effect.
Did the imbalance cause the mental health issue or did the mental
health issue cause the imbalance?
Serotonin
• Serotonin has long been linked to depression.
• One treatment for depression is SSRI (Selective Serotonin
Reuptake Inhibitors).
• These increase the amount of serotonin in the body.
•
Our senses activate nerve cells. This activation goes along the neural pathway.
This message needs to make it to the brain in order to succeed. Serotonin
helps transfer these messages across the synaptic cleft. Once this happens the
serotonin is taken back into the pre-synaptic cell to wait for further stimulation.
If the level of serotonin is low then
the message may not get across.
Some research has found that
taking drugs that reduce the levels
of serotonin lowers mood (Young
and Leyton) and this is also
supported by research on mice
(Sachs et al.) However, further
research has found no link in mice
(Perez et al.).
Dopamine
• Excess dopamine has long been associated with schizophrenia.
• Treatments include drugs that block dopamine receptors.
• By blocking the receptor you lower the level of dopamine in the
post-synaptic cell.
Anxiety
• Anxiety has been linked to serotonin and norepinephrine.
• Research is not concrete, but evidence from drug companies (which
may have a vested interest) suggests that SNRI’s (SerotoninNorepinephrine Reuptake Inhibitors) do work for anxiety.
The genetic explanation
• There is some evidence that some disorders are passed through
genetics.
• Research on this often involves the use of monozygotic twins
(identical twins) and dizygotic twins (non-identical twins).
• Also adoption studies are useful when trying to see the impact of
genes.
• How would the use of twins and adoption be used to see the impact
of genes?
The genetic explanation
• So if identical twins are separated (and so have a different
environment) but both have the same disorder then you could
conclude that genes play a role in mental health.
• Often research looks at parents with a mental health issue and then
investigates whether their children also develop the disorder.
• If the concordance rate (both parent and child have the disorder) is
high then genetics would seem to play a larger part. If concordance
is low then environmental factors may play a larger role.
Gottesman and Shields (1976)
• Looked at many adoption and twin studies.
• All of the studies found higher concordance rates for related pairs
but never 100% (suggesting that genes play a role but are not the
only factor involved).
• For example, in their 1972 study they found a concordance rate for
schizophrenia of 58% for monozygotic twins and 12% for dizygotic
twins.
Evolutionary theory
• This suggests that behaviour that has had a positive effect becomes
a trait in humans and those who had this trait initially mate and pass
this on in their genes.
• Ohman (1975) looked at this in regard to phobias.
• Ohman found that it was easier to condition a fear of snakes than
houses or faces. This suggests that a fear of snakes is biologically
prepared, thus supporting the evolutionary theory.
Brain abnormality
Brown et al. (1986) studied the brains of 41 patients with schizophrenia
and 29 with an affective disorder.
The brains of those who had schizophrenia were 6% lighter and had
lateral ventricles that were larger in the anterior and particularly in the
temporal horn section. They also had significantly thinner
parahippocampal cortices.
Brain abnormality
• Weinberger (1992) looked at identical twins not concordant for
schizophrenia.
• MRI scans found differences in brain structure mainly in the
prefrontal cortex and hippocampal volume.
• As technology has improved, so has studies looking into brain
abnormalities. However, research still has the cause and effect
issue.
Strakowski et al. (1999)
• Found that patients with bipolar disorder had significant differences
in the volume in the prefrontal, thalamic, hippocampal, amygdala,
pallidal and striatal regions compared to a control group.
• The amygdala differences were the biggest. This has high face
validity as the amygdala controls mood.
Brain volume
• Patients suffering from depression have a smaller hippocampal
volume than non-depressed people.
• Cortisol (a hormone released when stressed) can destroy
hippocampal cells. This could reduce the effect of serotonin and, as
we have previously studied, this impacts mood.
Positron Emission Tomography (PET)
• These scans can be used to monitor brain activity.
• Baxter et al. (1992) looked at metabolic rates in patients with OCD.
• Behaviour changes due to drug treatments correlated with a
reduction in brain activity in the right caudate nucleus.