Early-life experience and development

Professor Bruce McEwen discusses the dramatic impact early-life events can have on development.

The now classic studies of the late Seymour Levine and colleagues [and] Victor Denenberg showed that separation of pups from their mothers – this is rat or mouse pups – early in life for brief periods of time, like ten minutes a day, during the first two weeks before the eyes open leads to a more laid back personality, if you will. Other studies by people like Michael Meaney and so on, and Robert Sapolsky, I should add, have shown that these animals age more slowly, they have a longer life span, in general. Of course, then, the Meaney and Moshe Szyf studies have shown that there is a modification of DNA, the methylation or demethylation of cytosine bases in certain genes, that has an epigenetic and even trans-generational effect. So, a mother who has a …well, and that the mediator of these handling effects that Levine and Denenberg originally found is actually the amount of maternal care that the mother pays attention – how much licking and grooming occurs. The more licking and grooming, according to the Michael Meaney view, the more laid back the animals will be, the longer the life they will have, the more, perhaps, cognitively sharp they will be. But you have to remember, that’s in a safe environment; if it’s in a dangerous environment, then having a more anxious personality, a more wary personality, may actually be better for survival, so it’s very much dependent on the living environment, and you can easily extrapolate that to people.