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 blood-

circulation 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