Transcript Biological explanations of depression

PSYCHOPATHOLOGY
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46% MZ twins
20% DZ twins
(McGuffin et al. 1996)
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Genetic predisposition
Environmental triggers
Kendler et al. (1995) – Virginia twin study
Women genetically predisposed (twin has the
disorder) more likely to develop depression if
they have negative life events than women
who were not genetically predisposed.
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Neurotransmitter activity
Chemical messengers in the nervous system
Associated with reward and punishment
Help to regulate the hypothalamus
Involved in sleep, appetite, sexuality and
physical movement
Key areas affected in depression
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Low levels of Noradrenaline implicated in
depression
Support for this idea comes from the use of
drugs which affect Noradrenaline levels
Reserpine is a drug given for high blood
pressure.
Reserpine depletes levels of Noradrenaline
Depression is an unwanted side-effect of
Reserpine.
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Antidepressant drugs such as tricyclics and
Monamine Oxidase Inhibitors increase
amounts of Noradrenaline and Serotonin in
the synapses.
They have been found to be effective in
relieving the symptoms of depression.
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Selective Serotonin Reuptake Inhibitors
(SSRIs) such as Prozac have negligible effects
on Noradrenaline.
SSRIs are effective.
This suggests that serotonin has a role in
depression rather than Noradrenaline.
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It is not a simple situation.
Neurotransmitters have a complex
relationship with each other and links with
different aspects of human behaviour, e.g.
Noradrenaline – energy,
serotonin – rumination on grief, despair and
guilt,
Dopamine - pleasure
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Drug treatments have effects on the brain
other than just on neurotransmitters.
It is not certain that it is the change in
neurotransmitter levels that brings about the
effectiveness of the drug.
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Drugs alter neurotransmitter levels
immediately.
However, mood symptoms are not relieved
for several weeks.
This is another indication of the difficulty of
trying to attribute depression to
neurotransmitters.
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The change in levels of neurotransmitters
could be a result of depression rather than a
cause of it.
Cortisol is a stress hormone.
The hypothalamus regulates cortisol levels.
When Noradrenaline levels are low the
hypothalamus loses this ability.
 High levels of cortisol are often found in
depressed people.
 However, high levels of cortisol are not specific
to depression (they are also found in people with
anxiety disorders).
 It is not clear whether raised levels of cortisol are
an effect or a cause of depression.
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The frontal
cortex
 Especially the
anterior
cingulate
 Comes up with
sad abstract
thoughts
 And gets the
limbic system
involved.
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The biological
approach to explaining
depression suggests
that it is a disease in
the same way that
diabetes is a disease.
However, this is a
reductionist approach.
 It is too simplistic to
ignore psychological
factors.
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