Stress and the Developing Brain

Stress, is it the root of all evil?  What does chronic stress do to the brain?  To neurodevelopment?  In a world that is now filled with an abundance of daily chemical, physical and emotional stressors, we must take time to fully understand the global ramifications of stress.  Stress induces an upregulation of cortisol output (a stress hormone) which eventually weakens the adrenal glands.  In turn, increased cortisol will alter neurotransmiiter levels; primarily lowering serotonin (the so-called happy hormone) and dopamine (the 'pleasure' hormone).  Since serotonin is a precursor to melatonin, this can have an affect on sleep.  Often those with low serotonin have "anxiety of the brain" and have trouble falling asleep.  Low dopamine levels can also lead to trouble with insomnia.  Since sleep deprivation is a major problem in this country, we must look to the evil roots of stress as a primary problem.  Cortisol will also be upregulated in those with blood sugar metabolism issues; another major problem underlying so many health problems, including sleep.

Frontal lobe deficit is a common finding in many individuals that have been diagnosed with ADHD, schizophrenia and other mental disorders as well as various learning disorders.  Another common finding with frontal lobe deficit/dysfuntion is that of low dopamine.  The frontal lobe is our "reasoning" or "rational" center of the brain.  When the frontal lobe is weak, a person will be driven by the primitive limbic brain which will drive the amygdala and the stress response even higher; causing dysregulation of the HPA axis.  So, one must look at the broad ramifications of chronic stress and the affect on the brain, hormone dysfunction and mental illness.  

Chronic stress creates long-lasting changes in brain structure.  Daniela Kaufer, UC Berkeley associate professor of integrative biology, and her colleagues, found that under stress there was a stronger connectivity made between the hippocampus and the amygdala – the seat of the brain’s fight or flight response – and lower than normal connectivity between the hippocampus and prefrontal cortex, which moderates our responses, this results in a child 'pre-wired' for anxiety and a heightened stress response.

Sadly, so many children are being born with their HPA axis already compromised.  One study showed that exposure to elevated concentrations of cortisol early in gestation was associated with a slower rate of development over the first postnatal year and lower scores on the mental development index of the Bayley Scales of Infant Development (BSID) at 12 months. (1)  Prenatal stress does not only alter activity of the hypothalamo-pituitary adrenal axis permanently, but also changes activity of the second limb of the stress axis, the autonomic nervous system.


(1) The Timing of Prenatal Exposure to Maternal Cortisol and Psychosocial Stress is Associated with Human Infant Cognitive Development.  Child Dev. 2010 Jan; 81(1): 131–148.