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Psychoneuroimmunology (PNI)
- Mind, brain, and immune system are connected
- Mind can somewhat heal virally induced infections (i.e. warts)
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Stress
- Stressor - very individualized
- Most of time stress is a useful, good response
- There are negative feedback loops that turn the stress off
- HPA (hypothalamus-pituitary adrenal cortex) - more likely to be active during chronic stress; incr cortisol levels in stress and depression
- SNS - fight or flight response; epinephrine
- PNS - opposes SNS; involved w/ release of oxytocin
- Acute stress - activation of immune system
- Chronic stress - suppression of immune system (poverty, chronic diseases, people w/ terrible marriages, etc); incr risk of infection, cancer, allergies, autoimmune diseases
- Reactivity - react to environment; always on edge to world around us; causes acute blips of stress
- Some people can't launch an adequate stress response (inadequate cortisol response)
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Models and theories of stress
- Life stress model - more negative life events you have the more stress you have
- Lazarus and Folkman model - used today; stress is in your head, it is how you perceive it
- Allostasis model - new model; perception of stress and physiologic response, but we pay a price for those responses (allostatic load; risk for disease)
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Examples of allostasis
- Role of catecholamines in promoting adaptation by adjusting HR, BP to sleeping, waking, and physical exertion (can accelerate atherosclerosis, Type II diabetes)
- Lewis rat: incr susceptibility to inflammatory and autoimmune disturbances is related to inadequate levels of cortisol
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Physical vs. psychological stress
- Top-down stress activation - self talk about what is going on; threats vs. challenges; negative vs. positive
- Bottom-up stress activation - outside things that cause brain to react w/ stress response
- Classes of stress responses - defense vs. defeat (often leads to learned helplessness)
- Learned helplessness - learn that you can't change anything; hopeless
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Mirror stress
- Mirror your stress onto someone else
- Stress you respond with will be mirrored in someone else
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Social interactions
- Most positive social interactions seem to buffer stress and even improve immune function when stressed
- Negative life events produce their strongest effect on health when social support is low
- Marriage benefit - those who marry even if get divorced, live longer than single people
- Personality needs to be considered (A, B, C personalities; depression; pessimism)
- Type A - time driven, can't wait, hostile, multi-tasker, talk fast
- Type B - relaxed, easy-going, lack sense of urgency, disengaged
- Type C - more likely to get autoimmune disease or cancer, won't allow themselves to feel emotion
- It is the perception not the actual amount or type of social support that makes a difference
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Humor
Laughter decreases cortisol and improves immunity
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Exercise
- Can be a stress buffer
- For those who like to exercise it improves immune function
- Elite athletes immune system suffers and they appear to be chronically stressed
- Older people who rate themselves as physically active have better health (fewer infections) and improved immune function
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Depression
- Known relationship with depression and poor health
- Pt's with CV disease who are depressed have two times the mortality
- Sleep disturbances in depression may contribute to mortality and may be through immune mechanisms
- CRH brain levels incr in depression
- Brain regulation of peripheral immunity through CRH mediated regulatory autonomic nervous system pathways
- HPA is dysregulated in depression (hypercortisol)
- Vegetative symptoms of depression are similar to the behaviors assoc with sickness (fatigue, social isolation, decr appetite, lack of interest)
- Antidepressant drugs decr pro-inflammatory cytokine expression
- Other influences: smoking, alcohol, lack of exercise, sleep disturbances
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Cytokine hypothesis
- CNS responds to peripheral blood levels of cytokines
- Cytokines do not appear to be able to cross blood brain barrier
- Cytokines in blood may produce a corresponding incr in neurological synthesis of cytokines and changes firing in certain parts of brain
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