BIOLOGICAL FACTORS
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Transcript of BIOLOGICAL FACTORS
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BIOLOGICAL FACTORS• role of genes in contributing to the
risk of developing major depression• role of neurotransmitters serotonin
and noradrenaline in major depression
• the function of antidepressant medication in management
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GENETICS
• A genetic link for depression is evident from– Family studies– Twin studies– Adoption studies
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Family evidence
• Having a first degree relative (parent or sibling) with depression appears to be a risk factor for depression.
• One parent with depression, risk of offspring developing depression - 25-30%
• Two parents with depression, risk of offspring developing depression rises to about 70%
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Twin studies• Major depression is more likely to occur in both
members of identical twins than non-identical twins.• According to one study, if one twin has major
depression…– 46% chance the other will develop major depression
(identical)– 20% chance the other will develop major depression (non-
identical)
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Adoption Studies
• Wender et al. (1986) studied the biological relatives of adopted people who had been hospitalised for severe depression.
• There was a much higher incidence of severe depression in these relatives than in those of a non-depressed control group
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• It is not yet clear HOW genes influence the development of depression.
• Social and psychological factors also influence the chance.
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NEUROTRANSMITTERS
• Two neurotransmitters have been thought to be involved in depression, noradrenaline and serotonin.
• It has been thought that the low levels of these neurotransmitters leads to depression and high levels to mania.
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• When neurotransmitters are released by the pre-synaptic neuron into the synaptic gap, they travel to the post-synaptic neuron. Any excess neurotransmitters are ‘taken back’ or ‘reabsorbed’ into the pre-synaptic neuron in a process known as reuptake.
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Serotonin
• Involved with appetite, sleep patterns & mood.
• Low levels associated with– Sad and anxious moods, hunger, disruptions to the
sleep cycle• Low levels of serotonin has been found in the
cerebrospinal fluid of depressed patients (McNeal, 1986)
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noradrenaline
• Involved with attention, alertness, states of arousal and the stress response
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ANTI-DEPRESSANT MEDICATION
• Medications designed to relieve the symptoms of major depression
• Often prescribed along side other psychotherapies
• Can take 2-6 weeks before they become ‘active’– An indicator that other factors may be involved
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• Types of neurotransmitters are classed based on whether they are designed to increase:– BOTH serotonin and noradrenaline in the brain– ONLY serotonin – most common in Australia– ONLY noradrenaline
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Selective serotonin re-uptake inhibitors (SSRIs)
• Block the reabsorption of serotonin by the pre-synaptic neurons that release the neurotransmitter.
• A normal or relative high level of serotonin is then allowed to accumulate in the synapse and influence the activity of the post-synaptic neuron
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• Fig 8.16 p264
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