Download Stress—Current Concepts

Stress—Current Concepts
Anna Nagy, M.A.
Doctoral Candidate, Psychology
Background
• Many unanswered questions
• Cumulative effects of stress?
• Individual differences in stress response;
vulnerability to disease and psychological
disorder
• How can we quantify changes? Adaptive
mechanisms? Damage?
Stress and its Mediators
• Stress includes major life
events, trauma, abuse
(work, home, or
environment), daily
hassles, physical
challenges
• Coping
• Both acute and chronic
stress can have long term
consequences (severity)
Individual Responses
• Determined by:
– Perception of the situation & coping
• Crucial in determining behavioural and physiologic
responses
• Affects ability to adjust to chronic or repeated stress
– General state of physical health (includes
behavioural and lifestyle choices)
• May be genetic component
Coping—Effects of Social
Support
Current Concepts Not Sufficient
• Individual variability
– Not explained by genetics
– Gradients of health across socioeconomic levels
in Western societies not explained by genetics
– PTSD (across population; emergency
workers/paramedics)
Stress Affects Health
• Physical condition affects ability to respond to
stress
• Stress linked to various physical conditions:
– Family instability linked to incidence & severity of
insulin dependent diabetes (Hagloff et al., 1991)
– Chronic stress linked to insulin resistance (risk factor
for non-insulin dependent diabetes) (Raikkonen &
Adlercreutz, 1996)
– Stress linked to deposition of abdominal fat (risk factor
for coronary heart disease and diabetes) (Bjorntorp, 1990)
Stress Affects Health
• Acute Stress Enhances Immunity—
– Enhances traffic of lymphocytes and macrophages to
the area of need (‘delayed-type hypersensitivity’)
– Dependent on adrenal secretion; last 2-5 days
– Enhances responses for which there is an immunologic
memory (beneficial for cancer or tumour cell, but
pathologic for autoimmune or allergic responses)
• Can you think of any diseases where this might be a factor?
Stress Affects Health
• Chronic Stress Suppresses Immunity—
– Delayed hypersensitivity response severely
inhibited (Poteliakhoff, 1981; Ur, White & Grossman, 1992;
Buske-Kirschbaum et al., 1997)
• Increased severity of common cold
• Recurrent endotoxemia (increases HPA activity and
decreases production of cytokines)
(See McEwen, 1998; 2003 for review)
Stress and Immune Function
Stone & Neale, 1984
Stress and Health
• Cardiovascular disorders
– Diseases involving the heart and bloodcirculation system
• Essential hypertension
– Physical stress and blood-pressure increase
• Predisposing factors
Allostasis
• Allostasis: ability to achieve stability
through change—crucial to survival
• Accommodation: Body protected by
various systems including ANS, HPA,
cardiovascular, metabolic and immune
systems
Allostatic Load
• Allostatic Load: long term effects of the
physiologic response to stress.
– Wear and tear from chronic over-activity or
under-activity of systems
The Stress Response and the
Development of Allostatic Load
Stress Response and Development of Allostatic Load.
(McEwen, 1998)
Current Topics
• Effects on Cognition/Learning and Memory
– Animal research—How stress affects the brain
• Hippocampus—high concentration of GC receptors
• Stress=Increased cortisol secretion in most cases
• Atrophy of dendrites/Effects on neurogenesis
– Sex differences
– Suggestive Evidence in humans
• Hippocampal volume loss? (Cushings, Depression, PTSD)
• prevent access to contextual info (may lead to enhanced fear
based memory (PTSD))
• Caregiver study
• Aging Studies
• Allostatic Load
Four Situations Associated With
Allostatic Load
• Frequent Stress
– Surges in blood pressure related to myocardial
infarction in susceptible persons
– Lack of adaptation to frequent stressor of the
same type (ie public speaking)
– Inability to shut off responses
Four Situations Associated With
Allostatic Load
• No Adaptation to Repeated Stressors in
Some Individuals
– Fear of public speaking
– Phobias
Four Situations Associated With
Allostatic Load
• Failure to shut off stress response after
stressor abates
-evidence in aging animals
-allostatic systems may eventually wear out or
become exhausted
-hippocampus vulnerable link in HPA
regulation and in cognition
-“glucocorticoid-cascade hypothesis”
HPA
Four Situations Associated With
Allostatic Load
• Inadequate responses in some allostatic
systems=compensatory responses in other
systems (disruption of counter-regulatory
mechanisms)
– Eg. Cort secretion not increased in response to
stress=increase in secretion of inflammatory cytokines
(autoimmune diseases/inflammatory diseases)]
– Hyporesponsiveness (fibromyalgia, chronic fatigue
syndrome, PTSD)
Discussion
• Implications for Health
– Stigma?
– Social Change?
– McArthur Studies
– Duxbury Study
– Groupwork (if time permits)
Summary
• Effects of Stress—Current Concepts:
– Cognition/learning and memory
– Allostatic Load
– Implications for health