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What Studies on ‘Unloved’ Rats Tell us about Effects of Childhood Trauma



It is being increasingly recognized by research psychologists that the environment we are brought up in has a critical effect upon our later development and functioning. As in all areas of medical research, animal studies play a vital role in helping us to understand the possible causes of human psychological pathology.

Key studies on how early experiences can have adverse effects on psychological functioning have been conducted on rats. In one important study, it was found that baby rats who were raised by mothers who showed them little affection (affection in the rat world being demonstrated by licking) and were rarely licked by their mothers incurred damage to the way in which their brains developed (this was discovered by dissecting and examining their brains after death).

Baby rats who had been raised by their mothers in an affectionate way, however (i.e they received their fair quota of loving maternal licks), developed completely healthy brains; specifically, they had far more receptors in a brain region called the HIPPOCAMPUS – these receptors, greatly lacking in the ‘unloved’ rats, are considered to be crucial in the role of regulating (controlling and damping-down) stress responses (meaning they would be much better at tolerating stress in later life).

Further study has demonstrated that deprivation of affection damages vital DNA strands in rats and it is a knock-on effect of this damage which depletes the quantity of stress-reducing receptors in the brain.

It can clearly be inferred from the above findings that the problems the ‘unloved’ rats developed with their ability to tolerate stress as adults were NOT caused by inherited genes, but by damage down to their DNA by THE ENVIRONMENT IN WHICH THEY WERE RAISED (an environment in which they were deprived of maternal affection).

The perennial question may be raised in response to the above findings that that’s all very well, but can we extrapolate those findings to human beings? (my own view, for what it’s worth, is, not least because of our evolutionary history and the similarities between human brains and those of our furry, nose-twitching, be-whiskered little ratty friends, is that we can do so quite legitimately). However, for those who remain unconvinced, related studies have been conducted on human beings. I summarize one such study below:


– the study involved the dissection and examination of 36 human brains, post-mortem (obviously)

– of the 36, 12 had died of natural causes (GROUP A) and 24 had died by suicide

– of the 24 who had died by suicide, 12 had suffered serious childhood trauma (GROUP B). The other 12 had no (GROUP C).


GROUP B (those who had died by suicide AND suffered severe childhood trauma), like the ‘unloved’ rats, was found to have A GREATLY DEPlETED NUMBER OF BRAIN RECEPTORS RELATED TO STRESS REGULATION/CONTROL. This was not true of groups A and C.


These studies suggest that both rats and humans can incur serious damage to the way in which their brains physiologically develop, due to early life trauma, affecting their abilities to tolerate stress in later life.


Ian C. Hellstrom et al.,(2012). Maternal licking regulates hippocampal glucocorticoid receptor transcription through a thyroid hormone–serotonin–NGFI-A signalling cascade. Philos Trans R Soc Lond B Biol Sci. doi: 10.1098/rstb.2012.0223PMCID: PMC3405683PMID: 22826348.




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


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