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What is the biological explanation of depression
The monoamine hypothesis
What does the monoamine hypothesis claim to be the cause of depression
Less monoamine molecules are available for binding to receptors than needed, meaning they fail to regulate the limbic system- the centre for emotion in the brain
How may having too much monoamine oxidase cause depression
The monamines would be broken down too quickly by this enzyme so the brain would run out
What are the three main monoamines that may influence depressive symptoms
Dopamine, serotonin, norepinephrine (noradrenaline)
What is the role of serotonin
Regulating mood, well-being, stomach-functioning and other monoamine neurotransmitters
Which depressive symptoms may be directly caused by a lack of serotonin
Reduced appetite, low mood, illogical thinking patterns
How did Wender and Klein’s study support the monoamine hypothesis
A drug that lowered noradrenaline levels of animals made them sluggish and inactive- symptoms associated with depression
What is the role of noradrenaline
Regulating heart rate, concentration, attention, energy, alertness
What depressive symptoms may be caused by a lack of noradrenaline
Disruption of sleep patterns and lack of energy
What is the role of dopamine
Regulating motivation, reward, pleasure
What depressive symptoms may be caused by a lack of dopamine
Reduced attention, motivation and interest in pleasure
How is the successful use of drug treatments a strength of the monoamine hypothesis
If the drugs work then the theory has predictive validity as it suggests that increasing monoamine levels may reduce depressive symptoms
How does Meyer’s research support the monoamine hypothesis
He found that depressed patients who had not taken antidepressants for 5 months had significantly higher monoamine oxidase levels in all brain areas than clinically normal controls, which suggests they had lower levels of monoamines
How is therapeutic delay a weakness with the monoamine hypothesis
If low levels of monoamines were the sole cause of depression then drug treatment should be effective immediately
What is the biological treatment for depression
Drug treatment: SSRIs, MAOIs, SNRIs and NaSSAs
What do MAOIs stand for?
Monoamine oxidase inhibitors
How were MAOIs discovered
By accident when researchers noticed that an anti-tuberculosis drug had the side effect of improving mood
What do MAOIs do
Inhibit monoamine oxidase, which breaks down serotonin after reuptake. This increases availability of serotonin for future release into the synapse, therefore improving mood levels. MAOIs increase all monoamine neurotransmitters, including dopamine and noradrenaline
Give an example of a MAOI
Phenezine
What do SSRIs stand for
Selective serotonin reuptake inhibitors
When were SSRIs developed and why were they necessary
1980s because MAOIs are effective but have bad side effects
What do SSRIs do
Inhibit reuptake of serotonin by blocking the serotonin transporters so more serotonin is available in the synapse to bind with the post-synaptic neuron
What is the most commonly prescribed type of antidepressant in the UK
SSRIs
Give an example of an SSRI
Fluoxetine
What do SNRIs stand for
Serotonin-noradrenaline reuptake inhibitors
What do SNRIs do
Block reuptake of both serotonin and noradrenaline (in a similar way to SSRIs)
Give an example of a SNRI
Duloxetine
What do NaSSAs stand for
Noradrenergic and specific serotonergic antidepressants
Give an example of a NaSSA
Mirtazapine
Who are NaSSAs used for
People who have not benefited from SSRIs or SNRIs because they were ineffective or had intolerable side effects (e.g. sexual dysfunction)
How do NaSSAs work
They inhibit reuptake of serotonin and noradrenaline (like SNRIs but to a lesser extent) but also block certain types of serotonin and noradrenaline receptors to enable an increase in activity of the key receptor that improves mood
What is the key receptor that NaSSAs work to increase the activity of
5-HT1A
How is the existence of opipramol a weakness to the monoamine hypothesis
It alleviates depressive symptoms but doesn’t contain any mechanisms that effect monoamines so monoamines can’t be the only cause of depression
What does Kirsch believe about antidepressants
They are only effective due to the placebo effect
What did Verisani find from his double blind trial of noradrenaline reuptake inhibitors (NRIs)
The NRIs improved mood of depressed patients more than a placebo drug
