Biological basis of anxiety (Andrew Young)

What is anxiety

normal physiological responses to stress (danger)

• increased vigilance/arousal, prepare for flight or fight

What is an anxiety disorder

anxiety response but with intensity of feelings out of proportion to the ‘danger’

• excessive anxiety leading to maladaptive, atypical, irruption behaviour, and personal distress

Stress response involves activation of

hypothalamus-pituitary-adrenal (HPA) system

Anxiety is a what type of response which leads to what

a homeostatic response to the stressor leading to physiological adaptations to return the system to a set point

Increasing what function reduces anxiety

GABA function

• e.g. benzodiazepines

Why does increasing GABA reduce anxiety

• anxiety is often linked to overactive neural circuits in areas like the amygdala

• increasing GABA function (for example, with benzodiazepines) makes neurons less excitable

• this reduces excessive signaling in anxiety-related circuits, producing a calming effect.

Current pharmacological treatment of anxiety disorders use

antidepressants with serotonergic or noradrenergic action

What anxiety disorders do SSRI antidepressants are effective in controlling

• social phobias

• panic disorder

• generalised anxiety disorder

• PTSD

• some OCD

For SSRI antidepressants to be effective in controlling anxiety disorders does it require for a higher or a lower dose

high doses than for antidepressant action

Of using SSRI antidepressants to control anxiety disorders a … imbalance has been reported in … and …

serotonin imbalance has been reported in panic disorder and OCD

SSNRI antidepressants are helpful in treating …

panic disorder

What is the stress response, describe it

when your body perceives stress, it triggers a series of events in the brain and body

this involves the HPA axis:

1. Hypothalamus (in the brain)

• Detects stress and releases CRH (corticotropin-releasing hormone).

2. Pituitary gland (also in the brain)

• Responds to CRH by releasing ACTH (adrenocorticotropic hormone) into the blood.

3. Adrenal glands (on top of the kidneys)

• ACTH stimulates them to release cortisol (the stress hormone).

Effect:

• Cortisol prepares the body for “fight or flight” by increasing energy availability, alertness, and suppressing non-essential functions temporarily.

The stress response is under direct modulatory control of

• hippocampus - inhibitory

• amygdala - excitatory

What is the relation of anxiety to a stressor

the homeostatic response to a stressor

• physiological adaptations

  • involves inhibition of hippocampus and activation of amygdala

• anxiety is a normal response

Why do anxiety disorders occur

when anxiety is persistent and out of proportion to the stressor

What is the septo-hippocampal system

the septo-hippocampal system is a brain circuit that connects the septal nuclei (in the basal forebrain) with the hippocampus

• it’s a control and communication pathway that helps the hippocampus regulate stress, emotions, and memory

What does septal nuclei do

mostly cholinergic and GABAergic neurons that send signals to the hippocampus

What are the functions of the septo-hippcamapal system

• modulation of hippocampal activity: Helps control excitability and rhythm of the hippocampus.

• inhibition of stress responses: The system can dampen the HPA axis, reducing excessive cortisol release.

• memory and learning: Important for spatial memory and attention.

What is the stress-diathesis model

• mental illness occurs when stress exceeds a person’s ability to cope, interacting with their underlying vulnerability

  • someone with a high diathesis may develop illness with relatively minor stress

  • someone with low diathesis might handle major stress without becoming ill

“The stress-diathesis model suggests that mental illness arises when an individual’s underlying vulnerability (diathesis) interacts with environmental stress, so illness occurs only if stress exceeds their coping threshold.”

Anxiety disorders can also link to

depression

• both use similar or even the same antidepressants