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Early-Life Separation From Mother : What Experiments On Mice Tell Us.

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The Study: A Mouse Model Of Early-Life Stress :

This experiment was conducted to look at the effects on mice of early-life stress. It involved separating baby mice from their mothers for three hours per day for each of the first ten days of their lives.

Results Of The Study :

It was found that the effect of this early-life separation from their mothers caused these baby mice to grow up into adults who were significantly more highly stressed than mice who had not been removed from their mothers in early life; in particular, it was found that they ‘over-reacted’ to mild stressors.


The Underlying Mechanism – The Effect Of Stress At A Genetic Level :

The study also found that the early-life stress that the baby mice suffered adversely affected (due to decreased DNA methylation) the ARGININE VASOPRESSIN (AV) GENE.

  • This led to an increase in the mice’s production of ARGININE VASOPRESSIN

which, in turn…

  • Increased their stress-response in adulthood.

In other words, it seems that the mice’s early-life stress harms their AV gene, which, in turn, makes them more susceptible to the adverse effects of stress when they become adults.

Other, Similar Research (But Involving Rats) :

Similar research has been carried out on rats, giving similar results (although, in the case of the rats, a different gene was adversely affected by early-life stress; I wrote about this in an article I previously published on this website, it is entitled: What Studies On Rats Tell Us About The Effects Of Childhood Trauma. 

To What Degree Can We Extrapolate From Such Findings In Order To Elucidate Effects Of Early-Life Trauma In Humans?

In a study (Meaney et al) of samples of human brains of individuals who had tragically committed suicide, the researchers grouped the brains they were examining into two categories :

  • CATEGORY ONE: Brains of individuals who had committed suicide AND had experienced significant childhood trauma
  • CATEGORY TWO: Brains of individuals who had committed suicide but had NOT experienced significant childhood trauma

What Differences Were Found Between The Brains From CATEGORY ONE And The Brains From CATEGORY TWO?

  • CATEGORY ONE: It was found that in this group the cortisol receptor gene in the hippocampus had been affected in a way that led to HIGHER LEVELS OF CORTISOL (a stress hormone) circulating in the bloodstream which would have resulted in members of this group, when still alive, being particularly susceptible to the adverse effects of stress.
  • CATEGORY TWO: It was found in members of this group that the cortisol receptor gene had been significantly less adversely affected than in members of group one.

Conclusion :

The parallels between the findings of the animal studies and the studies of human brains (as described above) suggest that some of the findings from the experiments on rodents in relation to the effects of early life stress may well be applicable in helping us to understand how early life stress can affect humans.


David Hosier BSc Hons; MSc; PGDE(FAHE).