Why Childhood Stress Crimps Academic Performance
It reflects an ancient evolutionary pattern but calls for urgent change.
Posted Mar 18, 2015
Animals from an environment full of risk remain vigilant and avoid exploring their surroundings. This promotes survival but has the indirect consequence of reducing their cognitive ability. A similar pattern applies to humans and shows up as academic under performance.
The environment-cognition connection was established in animal enrichment experiments. Researchers upgraded the drab environment endured by lab rats by providing them with a changing selection of toys to play with (1). The enriched group were significantly better at learning complex mazes when tested as adults. In effect, they had become more intelligent. Indeed, analysis of their brains found that neurons had more extensive branching, implying that they could process more information.
Stressors inhibit curiosity and therefore block brain enrichment effects. Animals growing up in a stressful environment are also more sensitive to stress as adults (2).
By now, the evidence that early stress undermines academic performance of children is very clear. Mothers who experience unusually stressful pregnancies give birth to youngsters who test low on cognitive ability at 18 months—a difference equivalent to a 10-point deficit in adult IQ scores.
Poverty is a complex stressor and it does a great deal to perpetuate social status differences in a society where social mobility mostly requires educational success.
Children exposed to domestic violence in the home score lower on IQ tests, and it would be surprising if psychological stress had nothing to do with this (3).
Psychological stress may crimp intelligence, and school performance, through several different pathways, of which inhibiting intellectual curiosity and exploration is the most obvious.
We know that an enriched environment promotes growth and diversification in the connections formed by the brain's neurons. Psychological stress has the opposite effect and this phenomenon is obvious to gerontologists who notice that senile dementia worsens as a result of severely stressful experiences such as a bitter argument with a close friend.
Stress hormones effectively undo the beneficial effects of enrichment and prune back the branching of dendrites. It is no exaggeration to say that high levels of stress hormones, such as cortisol, are toxic to the brain (4).
Stress in childhood can impair intellectual function much as lead poisoning does but the effects may not be direct. A child who is afraid much of the time is likely to spend most of his time at home, or wherever he feels safest and is less likely to initiate social contacts, explore the physical environment, participate in neighborhood sporting activities, or visit a library.
This phenomenon was highlighted in a well-known study of IQ as a function of parental income (5). Parents in poorer homes spent a lot less time talking to their children that is negative for their academic prospects because it is the equivalent of subtracting what is likely one of the most enriching experiences for small children, namely being engaged by their parents.
Even more disturbing is the fact that what parents had to say in poor homes was overwhelmingly negative, or scolding. In effect, they were piling on the neurotoxins whilst withdrawing the environmental enrichment. Small wonder that the academic chasm as a function of parental income can be so large.
Such findings seem uniformly grim but they also suggest a clear plan of action and if they did not, it would scarcely be much good discussing them.
2. Kalinichev, M., Easterling, K. W., Plotsky, P. M., and Holtzgman, S. G. (2002). Long-lasting changes in stress-induced corticosterone response and anxiety-like behaviors as a consequence of neonatal maternal separation in Long-Evans rats. Pharmacology, Biochemistry, and Behavior, 73, 131-140.
3. Delaney-Black, V., Covington, C., Ondersma, S. J., Nordstrom-Klee, B., Templin, T., Ager, L., et al. (2002). Violence exposure, trauma, and IQ and/or reading deficits among urban children. Archives of Pediatric and Adolescent Medicine, 156, 280-285.
4. Teicher, M. H., Andersen, S. L., Polcari, A., Anderson, C. M., & Navalta, C. P. (2002). Developmental neurobiology of childhood stress and trauma. Psychiatric Clinics of North America, 25, 397-426.
5. Hart, B. & Risley, T. (1995). Meaningful differences in the everyday experience of young American children. Baltimore, MD: Paul H. Brookes.