Lecture 8: Depression and Mood Disorders

depression

• cognitive symptoms → difficulty with concentration or making decisions

• behavioural symptoms → social withdrawal or agitation

• somatic symptoms → insomnia or hypersomnia

• affective symptoms → depressed mood and feelings of worthlessness or guilt

-DSM-5 breaks down depression into separate disorders with different criteria for each one

reactive depression

-triggered by a negative experience

endogenous depression

-no apparent negative life event

unipolar affective disorder

-major depressive disorder or major depressive episodes

bipolar affective disorder

-depression with periods of mania

-mania is the opposite of the depressive symptoms → the two alternate in a cycle

genetics (causes of depression)

-ascertained that mental health has a genetic component by looking at identical and non-identical twins

-look at concordance rate between sets of twins

-MZ twins have 39% concordance rate for depression compared to 27% for DZ twins

Brown - environment (causes of depression)

-looked at people of lower socioeconomic status and amount of severe stress in the previous year

-subjects who were suffering from depression experienced much more severe stress than the controls

-but many people experienced severe stress but did not get diagnosed with depression

diathesis-stress model (causes of depression)

• diathesis → internal, often a genetic component

• stress → something in the environment

-must have a predisposition towards depression and stress from the environment must occur in order to trigger depression

heritability (behavioural genetics)

-an estimate of how much variance in some characteristic within some population is due to differences in heredity

• bipolar disorder → 0.85

• major depressive disorder → 0.4

mono amine oxidase inhibitors

-first drugs used to treat depression

-monamine agonists → increases levels of monamines (norepinephrine + serotonin)

mono amine neurotransmitters

-monamines are split into:

• catecholamines → dopamine, adrenaline, noradrenaline

• indolamines → serotonin

serotonergic projections

-triggers amygdala → impacts how we think of the world and respond to stimuli

-this then triggers prefrontal cortex

noradrenergic projections

-has both dorsal and ventral projections

-diffuse projections → all over head and brain

monamine synapse

-causes serotonin to be released from synaptic cleft before being taken back up

-MAO inhibitors means there is more neurotransmitter left in the neuron to be released

tricylic antidepressants

-block reuptake in norepinephrine or serotonin synapse

-leaves more transmitter at the synapse

SSRIs

-serotonin synapse only

-serotonin is deactivated in the synapse by reuptake into the presynaptic neuron

-SSRIs blocks the reuptake of serotonin, thus increasing the activation of serotonin receptors

lithium

-used to treat bipolar disorder

-interferes with the second messenger system → works as a mood stabiliser

monoamine theory of depression

-anti-depressants work on monamines

-so depression is caused by a deficit of monamine neurotransmission

-some evidence of elevated receptors in depressed patients → to compensate for low levels of transmission

monamine and brain regions

-monamine neurotransmitters could modulate brain regions involved in emotion and cognition

-an overreactive limbic system and amygdala are implicated in affective disorders

-orbital and medial prefrontal cortex → ruminating and cognitions about the world

Beck’s cognitive triad

• negative views about the world

• negative views about the future

• negative views about oneself

learned helplessness

-dog is in a box with a barrier

-a tone indicates a shock

-dog must jump over barrier to avoid shock

-after dog has been in a condition where they cannot escape the shock → they no longer jump to the no shock zone

Seligman’s attributional model

-attributions of negative events

-three dimensions are:

• internal vs external

• global vs specific

• stable vs unstable

-depressed people tend to attribute negative life events to internal, stable, global causes