Depression and bipolar Flashcards
Outline the two main types of depression
Unipolar: low mood
Bipolar: also known as manic. low mood with periods of mania
Define dysthymia
Low grade but long term depression
What type of depression may be accompanied by delusions
Psychotic or major depression
What is lifetime prevalence of major depression?
4% in males 8% in females
Why is there a gender difference in depression and antidepressant efficacy?
Sramek et al., 2016: there is sex difference in antidepressant efficacy - body fat, hormone levels impact pharmacokinetics of drugs.
Females: harsher symproms, increased weight gain, younger onset, greater anxiety.
Theory: due to oestrogen and progesterone (as incidence of depression in women post menopause is similar to that of men). PET showed decreased serotonin synthesis in females.
SSRIs: females respond better than men and postmenopausal females have diminished response compared to younger females.
State the difference between reactive and endogenous depression
Reactive: depression due to external factors such as death, 75%.
Endogenous: due to biochemical reasons, 25%. No external factors
State the differences between treatment of endogenous and reactive depression
There is no differentriation in drug treatment.
How is depression diagnosed and what criteria is used?
DSM-IV Criteria for Major Depressive Disorder
Depressed mood/loss of interest or pleasure in daily activities for over 2 weeks.
Mood changes from person’s baseline.
Impaired functionality (social, occupational, educational).
Significant distress is caused.
Define anhedonia
Reduced ability to feel pleasure.
List symptoms of depression
Depressed mood or irritability (misery, apathy and pessimism)
Loss of motivation
Significant weight change
Insomnia or hypersomnia
Fatigue
Guilt, low self esteem feeling worthless
Loss of libido
Suicidal thoughts
State brain system/s associated with anhedonia and reduced drive and describe
Reward system (VTA, NAcc)
Decreased level of mesolimbic DA to VTA implicated, could also be due to decreased hippocampal activity via NAcc to VTA.
The NAcc generates behaviour aimed at acquiring rewards and activity of this region imporves hedonic tone (Willner et al., 2012)
State brain system/s associated with reduced energy and describe
HPA axis
Chronic stress induced adrenal exhaustion caused by activation of HPA axis (Herman et al., 2016)
State brain system/s associated with memory problems and describe
Hippo
Poor memory for positive and potentiated memory for negative events.
Possibly via stress mediated suppression of hippocampal neurogenesis (Dillon and Pizzagalli., 2018)
State brain system/s associated with attention and cognitive impairment and describe
PFC and ACC
Decreased ACC volume observd in depressed patients.
DBS therapy 50% of patients showed improved DSM-VI scores one year later (Willner et al., 2012).
State brain system/s associated with anxiety and describe
HPA
Again chronic stress
Explain evidence that shows that antidepressant treated brains are different to normal brains
Willner et al., 2012:
When successfully treated depressed patients are administered a DA blocker depressed mood returns.
People in normal state show slight improvement in mood when same block administered.
Do different antidepressants all work on different targets?
yes and no: will all have different primary effects but all known increase responsiveness of DA D2 receptors in NAcc and CREB expression in the hippocampus (Willner et al., 2012)
Is CREB expression anti or pro-depressant?
Both…
Hippo is anti
NAcc is pro
What does chronic administration of BDNF into hippocampus cause?
Increases neurogenesis.
What does chronic activation of HPA axis lead to?
Chronic CRH release - neurotoxic to hippocampal cells causing loss of glucocorticoid receptors in granule cells.
This leads to less BDNF production and atropy of dendrties.
Spatial memory in rodents and verbal declarative memory then impaired in humans.
Willner et al., 2012.
State reason why some people may be predisposed to depression
Negative experiences in early life such as abuse.
What hormone does CRH stimulate the release of and what does it do?
ACTH (adrenocorticotrophic releasing hormone) from the pituitary gland.
Causes secretion of cortisol from the adrenal glands and via negative feedback it inhibits release of CRH.
What impact does cortisol secretion have on ACTH?
Inhibits release via negative feedback.
Describe differences to do with HPA axis that depressed patients show
High levels cortisol, CRH.
Increased number of CRH-secreting neurons.
CRH binding sties reduced in frontal cortex.
Dysregulated circadian cortisol patterns.
What does blockade of CRF1 receptors produce?
Reduction in anxiety and depression symptoms.
What does admin of CRH produce?
Symptoms that resemble depression:
Decreased appetite
Sleep disruption
Decreased libido
Increased anxiety
Neophobia.
Define neophobia:
irrational fear of new or unknown.
Why are animal models of depression hard to design?
animals do not show human symptoms such as: guilt, suicidality… (Krishnan and Nestler, 2011)
What depressive symptoms can you measure in animals?
Anhedonia, helplessness and alterations in sleep and appetite(Krishnan and Nestler, 2011)
Outline evolutionary perspective of ‘depression’ in animals
(Krishnan and Nestler, 2011): depression is an analog of involuntary defeat strategy.
Animals percieve defeat in heirarchical struggle for resources.
NB: this is adaptive as use less energy and therefore not pathological.
Name and describe the three different types of validity in animal models. What needs to be taken into account regarding depression?
1) face: symptomatic homology
2) construct: similar cause
3) pharmacological: reversal via antidepressants.
1) anthromorphisation cannot be excessive
2) not possible due to incomplete etiology of depression.
3) in this model are we only treating depression that is monoamine sensitive?
(Krishnan and Nestler, 2011)
What is the fourth type of validity that needs to be developed
Same pathology in brain via postmortem examination of human…
Outline acute stress animal models
Forced swim: inescapable cylinlder of water, initial struggle then immobile.
Tail suspension.
In both of the above, increase immobility = more depressed.
(Krishnan and Nestler, 2011)
How do antidepressants impact acute stress models
Decrease immobility with no therapeutic delay (NB: antidepressants take over 2 weeks to work in humans)
What are SERT KO mice and how do they react to acute stress models of depression?
Serotonin transporters (reuptake): diff mouse strains show differential effects, both pro and anti.
V strange as would expect anti for all.
What effect does Isotretinoin have on animals and humans?
Also known as Accutane: acne treatment that increases risk of depression and suicide in humans.
In animals mice show increased immobility and decreased neuronal proliferation.
(Krishnan and Nestler, 2011)
Outline the learned helplessness model of depression
Exposure of animal to uncontrollable and inescapable stress such as footshocks.
When same animal introduced to same stress with easy escapse they either escape quickly or completely fail. Depressed fail.
Rats show: weight loss, altered sleep, loss of spinal synapses in hippocampus after this model.
(Krishnan and Nestler, 2011)
Describe social stress models for depression
Dominant animal: hard to replicate in lab and only in males
Social isolation: v easy
Give animal model of secondary depression
HPA axis dysfunction implicated in depression which causes altered glucocorticoid function.
Glucocorticoid receptor KO mice developed: increased acute stress immobility which is reversable with antidepressants.
(Krishnan and Nestler, 2011)
Outline the monoamine hypothesis
Depression: lack of amines
Mania: excess of amines
NADR/5-HT affecting drugs could help stabilise/elevate mood.
Support for monoamine hypothesis
MAOi’s increase concentration of amines by inhibition of catabolism are effective antidepressants.
Reserpine depletes monoamines and exacerbates depression.
Reuptake inhibitors increase concentration and time in synaptic cleft are effective antidepressants.
Problems with monoamine hypothesis
Pharmacological effects are correlated with blood plasma concentrations but therapeutic effects are delayed at least 2 weeks.
Some effective atypical antidepressants do not alter monoamine levels in the synaptic cleft.
Cocaine inhibits reuptake of DA, NA, 5HT but is not an effective antidepressant.
Precursor amino acids increase amine levels but are not effect antidepressants.