Low levels of the neurotransmitters serotonin and noradrenaline cause negative thinking.
SSRIs (selective serotonin reuptake inhibitors) raise serotonin levelsby blocking reuptake and have been found to lift the mood of someone with depression
Low levels of noradrenaline in the urine of those with depression
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Physiological explanations-Hormones
High levels of stress hormone cortisol also linked to D
Research into Cushings syndrome (caused by high levels of cortisol) show that it is linked to low levels of serotonin and depression
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Physiological explanations-Brain Structure
Brain scans that people with depression often have an overactive amygdala, the emotional centre of the brain
This could explan the over-emotional state of people with depression
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Physiological explanations-Genes
Many people with depression have a faulty 5-HTT gene-the serotonin transporter gene
17% of the general population will have depresison at some point in their life
DZ twins have a concordance rate of 20%
MZ twins have a concordance rate of 40-50%
If entirely genetic, this would be 100%
Biological parents of children with depression 8 times more likely to get depressed than adoptive parents
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Support for physiological explanations
McGuffin-Twin Study
177 pairs of same sex MZ and DZ twins where one twin had been diagnosed with depression
46% concordance rate for MZ twins, 20% concordance rate for DZ twins
TST strong genetic aetiology
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Methodology of physiological explanations
The twin, adoption adn brain research it is based on is objective, scientific and thus reliable
Effect of IV (MZ or DZ twin) on DV (risk of developing depression) enables controlled comparisons to be made
Evaluation: MZ twins are often treated more similarly than DZ twins
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Weakness of physiological explanations
Deterministic
Individuals have no control over hormones, genes or neurotransmitters
TST pessimistic
Evaluation: SSRIs like prozac can raise serotonin levels
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Psychological explanations-Distorted thinking
A cognitive idea is that depression is caused by nagative and distorted thinking
Beck found depressed people tend to have negative schemas
He developed the negative triad: pessimistic view of themselves, the world and the future
Beck believed this was caused by criticism from parents/teachers in early childhood
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Psychological explanations-Learned helplessness
Developed from Seligman's research with dogs
People who try but fail to control unpleasant life events like abuse learn to feel helpless
They do not learn coping strategies to cope with stressful life events like unemployment
This can lead to depression
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Support for psychological explanations
Langer and Rodin-enabling old people to make decisions had a positive effect on mental and physical health
Increased happiness, decreased helplessness and therefore depression
TST aetiology is closely related to learned helplessness
Could be used by social services to improve nursing homes
Shah and Waller found that people suffering from depression are more likely to describe their parents as affectionless than non-depressed people
TST criticism from parents can cause depression
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Methodology of psychological explanations
Based on unstructured interviews
Provide depth and insight and thus high on validity
However not consistent or reliable
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Weakness of psychological explanations
Reductionist
Only emphasises negative thinking and learning
Neglects genetics and brain chemicals
TST oversimplified view of depression
Diathesis-stress model: born with a genetic tendency but it takes lack of control over life to trigger it
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Applications
Depression is based on both nature and nurture explanations
Research is vital as it can lead to effective treatments
E.g. research into serotonin led to development of SSRIs, reseach into negative thinking led to CBT
The combination of these treatments has improved the lives of many with depression
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