title: Development of individual differences in stress responsiveness: an overview of factors mediating the outcome of early life experiences.
abstract: BACKGROUND
  Human epidemiology and animal studies have convincingly shown the long-lasting impact of early life experiences on the development of individual differences in stress responsiveness in later life. The interplay between genes and environment underlies this phenomenon.
  
  
  OBJECTIVE
  We provide an overview of studies investigating the impact of early life experiences on the development of individual differences in neuroendocrine stress responsiveness in adulthood and address (1) impact of environment on later stress phenotypes, (2) role of genetic factors in modulating the outcome of environment, and (3) role of nonshared environmental experience in the outcome of gene × environment interplays. We present original findings where we investigated the influence of nonshared experiences in terms of individual differences in maternal care received, on the development of stress phenotype in later life in rats.
  
  
  RESULTS
  Environmental influences in early life exert powerful effects on later stress phenotypes, but they do not always lead to expression of diseases. Heterogeneity in response is explained by the role of particular genetic factors in modulating the influence of environment. Nonshared experiences are important in the outcome of gene × environment interplays in humans. We show that nonshared experiences acquired through within-litter variation in maternal care in rats predict the stress phenotype of the offspring.
  
  
  CONCLUSIONS
  The outcome of early experience is not deterministic and depends on several environmental and genetic factors interacting in an intricate manner to support stress adaptation. The degree of "match" and "mismatch" between early and later life environments predicts resilience and vulnerability to stress-related diseases, respectively.
authors.affiliation: Division of Medical Pharmacology, Leiden/Amsterdam Center for Drug Research, Gorlaeus Laboratories, Leiden University, P.O. Box 9502, 2300 RA, Leiden, The Netherlands. s.claessens@lacdr.leidenuniv.nl
authors.forename: Sanne E F
authors.initials: SE
authors.lastname: Claessens
authors.forename: Nikolaos P
authors.initials: NP
authors.lastname: Daskalakis
authors.forename: Rixt
authors.initials: R
authors.lastname: van der Veen
authors.forename: Melly S
authors.initials: MS
authors.lastname: Oitzl
authors.forename: E Ronald
authors.initials: ER
authors.lastname: de Kloet
authors.forename: Danielle L
authors.initials: DL
authors.lastname: Champagne
mesh_terms: D000818:Animals; D004198:Disease Susceptibility; D006801:Humans; D008016:Life Change Events; D009490:Neurosecretory Systems / Q000378:metabolism*; D010641:Phenotype; D051381:Rats; D055500:Resilience, Psychological; D012307:Risk Factors; D013315:Stress, Psychological / Q000150:complications*