STRESS AND GROWTH

Prenatal Stress and Growth

 F.O.A.D. : Fetal Origins of Adult Disease  Fetus “learning” about nature of world outside

Starvation as Stressor  Food deprivation in mother during pregnancy  Result of famine, poverty, diet  Fetus “learns” that food is scarce

Metabolic Imprinting  Metabolic Imprinting: change in basal metabolism  Shifts permanently  Thrifty metabolism: fetus is more efficient at storing calories

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 )

Necessary Components  Undernourished as fetus  Plentiful food environment after birth

Birth Weight and Health  Decreased birth weight, increased risk of metabolic disorder  Lowest 25% Birth Weight: 50% higher rate of death from heart disease

Is this Specific to Starvation??

Animal Studies

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

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

Human Studies

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

Consequences of In-Utero Stress

 Reproductive system  Demasculinization: decreased testosterone  Anxiety & Depression  Effects on amygdala  Memory Deficits

Post-Natal Stress and Growth

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

Stress and Brain Growth

Stress and Brain Activity

Stress Dwarfism  om/watch?v=dEnkY2i aKishttp:// be.com/watch?v=dEnk Y2iaKishttp:// be.com/watch?v=dEnk Y2iaKis  King Frederick II  J.M. Barrie  “Genie”

Stress Dwarfism: Mechanism  Decreased Growth Hormone (GH)  Decreased response to Growth Hormone (GH)  Decreased Absorption of Nutrients  Increased Release of Hormone that inhibits GH

Harlow Studies: Maternal Deprivation

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

Complete Isolation

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]

Summary of Isolation Effects  Decreased growth  Decreased Cognitive Functioning  Decreased Social Functioning  Not reversed by foster care, after critical period

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

Protective Factors

Importance of Touch  Tiffany Field studies: premature infants in neonatal wards  Touch: Decreases cortisol release

Stress Immunization  Meaney Studies: after removal, mothers allowed to groom & comfort pups

Higher grooming after early stress results in lower stress later in life

Grooming results in altered gene expression

Adult Growth

Glucocorticoids & Bones  inhibit growth of new bones  Reduce calcium supply to bones  Results:  Decreased bone mass  Osteoporosis  Skeletal Atrophy  “pharmacological” effect

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)