Prospective investigation of stress inoculation in young monkeys.
Level 5 - mechanism / opinion, no new human data
Animal research (non-human primate model).
PubMed 15351772 · doi:10.1001/archpsyc.61.9.933
What was done
Twenty squirrel monkeys were randomized to either intermittent stress inoculation (IS; n = 11) or a nonstress control condition (NS; n = 9) between postnatal weeks 17 and 27. At postnatal week 35, mother-offspring dyads were evaluated in a novel environment for behavioral measures of anxiety (maternal clinging, mother-offspring interactions, exploration, food consumption) and endocrine markers (basal and post-stress ACTH and cortisol). At postnatal week 50, independent young monkeys were assessed for exploration and play in a wire-mesh box attached to their home cage.
What was found
In the novel environment test, IS compared with NS offspring showed diminished anxiety via decreased maternal clinging (P = .02), enhanced exploratory behavior (P = .005), and increased food consumption (P = .02). Mothers of IS offspring accommodated exploration more (P = .009) and served as a secure base more often (P = .047). IS offspring had lower basal plasma ACTH (P = .001) and cortisol (P = .001) concentrations, and lower post-stress ACTH (P = .04) and cortisol (P = .03). In the wire-box test, IS offspring showed enhanced exploratory (P < .001) and play (P = .008) behaviors. Exact baseline values, group means, effect sizes, and confidence intervals were not reported in the abstract.
Why it matters
This study provides prospective experimental evidence in primates that exposure to moderate early-life stress can promote subsequent neuroendocrine and socioemotional resilience rather than vulnerability.
Limits
The study is limited by a small sample size (n = 20), reliance on an animal model (squirrel monkeys) that may not fully generalize to humans, and follow-up limited to postnatal week 50 without long-term adult assessments. Absolute numerical values and confidence intervals were omitted from the abstract.
Cited by
- supports Studies in squirrel monkeys by researchers at Stanford showed that exposure to moderate adversity early in life is a key factor in cultivating later-life resilience.