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STRESS AND GROWTH
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Prenatal Stress and Growth
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F.O.A.D. : Fetal Origins of Adult Disease Fetus “learning” about nature of world outside
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Starvation as Stressor Food deprivation in mother during pregnancy Result of famine, poverty, diet Fetus “learns” that food is scarce
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Metabolic Imprinting Metabolic Imprinting: change in basal metabolism Shifts permanently Thrifty metabolism: fetus is more efficient at storing calories
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Adult Consequences Increased risk for obesity (1 st trimester) Increased Cardiovascular Disease (1 st trimester) Increased risk for Type II diabetes ( 2 nd & 3 rd )
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Necessary Components Undernourished as fetus Plentiful food environment after birth
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Birth Weight and Health Decreased birth weight, increased risk of metabolic disorder Lowest 25% Birth Weight: 50% higher rate of death from heart disease
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Is this Specific to Starvation??
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Animal Studies
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Pregnant rats exposed to shock Increased cortisol levels in both mother and pup As Adults, offspring show: Increased cortisol levels Larger stress response Slower recovery
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Mechanism Cause: increased cortisol in mother’s bloodstream Same effect by injecting mother with cortisol Consequence: fetal pup adapts by decreasing number of cortisol receptors HPA Negative Feedback Loop loses sensitivity Can’t shut cortisol off
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Human Studies
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Project Ice Storm 1998: Quebec Ice Storm Babies No electricity for 40 days Tested women who were pregnant Children tested at 6 months, and 2, 4, 5.5, & 6.5 yrs Results: Low birth weight Slowed language/cognitive development
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Consequences of In-Utero Stress
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Reproductive system Demasculinization: decreased testosterone Anxiety & Depression Effects on amygdala Memory Deficits
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Post-Natal Stress and Growth
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Maternal Deprivation Meaney Rat Studies: Pups separated from mother Inattentive mothers Rumanian Orphanages Lack of physical contact Results: increased basal cortisol levels Depressed behavior as adults
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Stress and Brain Growth
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Stress and Brain Activity
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Stress Dwarfism http://www.youtube.c om/watch?v=dEnkY2i aKishttp://www.youtu be.com/watch?v=dEnk Y2iaKishttp://www.youtu be.com/watch?v=dEnk Y2iaKis King Frederick II J.M. Barrie “Genie”
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Stress Dwarfism: Mechanism Decreased Growth Hormone (GH) Decreased response to Growth Hormone (GH) Decreased Absorption of Nutrients Increased Release of Hormone that inhibits GH
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Harlow Studies: Maternal Deprivation
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Summary two groups of baby rhesus monkeys were removed from their mothers: terrycloth mother: provided no food wire mother: attached baby bottle containing milk. Results: monkeys preferred terry cloth “mother”, even if it provided no food Conclusion: “Contact Comfort” important
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Complete Isolation
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Results of Total Isolation "severe deficits in virtually every aspect of social behavior."[11] Isolates exposed to monkeys the same age who were reared normally "achieved only limited recovery of simple social responses."[11] Some monkey mothers reared in isolation exhibited "acceptable maternal behavior when forced to accept infant contact over a period of months, but showed no further recovery."[11] Isolates given to surrogate mothers developed "crude interactive patterns among themselves."[11]
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Summary of Isolation Effects Decreased growth Decreased Cognitive Functioning Decreased Social Functioning Not reversed by foster care, after critical period
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Corfas, et al: Critical Period for Social Isolation Mice isolated for 2 weeks after weaning Results: decreased myelinization in prefrontal cortex; occurred only during this critical period Not reversed with reintroduction to social environment Conclusion: Social interaction necessary during critical period
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Protective Factors
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Importance of Touch Tiffany Field studies: premature infants in neonatal wards Touch: Decreases cortisol release
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Stress Immunization Meaney Studies: after removal, mothers allowed to groom & comfort pups
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Higher grooming after early stress results in lower stress later in life
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Grooming results in altered gene expression
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Adult Growth
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Glucocorticoids & Bones inhibit growth of new bones Reduce calcium supply to bones Results: Decreased bone mass Osteoporosis Skeletal Atrophy “pharmacological” effect
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Timing of stressor Landauer & Whitting study: Examined rites of passage 80 cultures Classified according to whether children subjected to physically stressful developmental rites Age during which stressor experienced Results: Age 6-15: Growth inhibited (-1.5) Age 2-6; growth stimulated ( +2.5)
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