The Science Of Depression 22.02.23

Question 1

What is the HPA axis?

Answer 1

The hypothalamus pituitary adrenal axis
Hypothalamus releases CRH in response to stress
This in turn produces ACTH
Causing adrenal cortex to release cortisol preparing body for fight or flight

Question 2

What is depression?

Answer 2

Low mood, anhedonia, low energy
- poor sleep
- poor appetite
- worthlessness
- guilt
- Hopelessness

Question 3

Due to the HPA axis what do people with depression have that is different?

Answer 3

• enlarged adrenals
• reduced negative feedback

Question 4

How does release of ACTH change with childhood maltreatment?

Answer 4

They have a higher release of this in response to stress
- even if swapped at birth it is all due to environmental factors rather than genetics

Question 5

How does stress affect the brain?

Answer 5

• causes Neuro-vulnerability
• affect dendrite formation
• reduces Neuro genesis
• particularly affects the frontal lobes and hippocampus

Question 6

Where in the frontal lobes are affected by stress?

Answer 6

Medial pre-frontal cortex (necessary for social cognition nhs evaluating emotion state) not that affected

Dorsolateral PFC (working memory and problem solving) has a large volume loss and affected more

Question 7

How does depression affect the hippocampus?

Answer 7

Reduced size (20%) volume loss
More time depressed - worse the volume loss
Learning based cognitive deficits
Irreversible volume loss
- hippocampus for memory so memory loss

Question 8

What is Neuro genesis?

Answer 8

Axons and dendrites grow and integrate into the already existing networks

Question 9

How does stress/ depression affect Neuro genesis?

Answer 9

• causes reduced Neuro genesis
• social dominance stress reduces the number of surviving new cells

Question 10

How does stress affect dendrites?

Answer 10

There are reduced neurotrophins e.g. BDNF expression is shut off. So dendrites did and not as many grow

Question 11

How does levels of BDNF vary with medication?

Answer 11

Low BDNF in unmedicated depressives
Normal to high in medicated
Lowest levels in post Morton’s of successful suicide victims

Question 12

How do antidepressants work?

Answer 12

• They affect and enhance GR (glucocorticoid receptor) expression and regulate HPA activity.
• serotonin binds to G protein receptor
• They increase neurogenesis
• They increase BDNF synthesis (which improves connectivity and increases the number of synapses)

Question 13

What is MDD?

Answer 13

Major-depressive disorder
This is Neuro degenerative disease of impaired plasticity

Question 14

What is the function of the default mode network?

Answer 14

• brains resting state
• involved in daydreaming
• spatial memory

Question 15

How does the DMN work in depression?

Answer 15

People find it hard to appropriately switch off their DMN in response to a task
- Unable to stay on topic etc or not go into a spiral

Question 16

What does the reduction in DMN cause?

Answer 16

The positive experiences or psychedelics and ego dissolution

Question 17

What is entropy?

Answer 17

Measure of disorder and chaos
- brain tries to reduce this (e.g. reduce surprise)
- it does this by making predictions
- top-down processing
- initially visual, then words predictions and core beliefs

Question 18

How is depression a disease of reduced plasticity?

Answer 18

Reduced connectivity at a cellular level and at an interpersonal level