Everyone talks about how bad stress is for health. You get sick more easily and over your head ‘it works worse’ … but,Do we really know what effects stress has on the brain?And what type of stress is the most damaging?
Two very interesting reviews have recently been published on the subject. Thomas Frodl and Veronica O’Keane feature inNeurobiology of Disease (2013) that a brain excessively and continuously exposed to stress suffers damage to its structure and functioning, and that these damages are mediated, among other things, by the toxic effects of cortisol. It is what is known asthe glucocorticoid cascade hypothesisdescribed by Robert Sapolsky in 1986. According to this hypothesis, chronic stress can produce brain changes that cause the axis that controls the response to stress (Hypothalamic-Pituitary-Adrenal -HHA axis) to go out of control. The brain structure known as the hippocampus is very sensitive to glucocorticoids, as it has many receptors for them. Glucocorticoids, like cortisol, allow the mobilization of energy resources to cope with stressful situations. However, when the hippocampus is overexposed to them it atrophies. The hippocampus plays an important role in learning andmemory, with what chronic stress would cause these functions to be altered. But in addition, the hippocampus has a regulatory function for HHA, providing it with inhibitory feedback (so that it stops secreting glucocorticoids). Paradoxically, a hippocampus that has been exposed in excess to glucocorticoids will have more difficulties to send that information back, with which there will be more of this substance and therefore more hippocampal damage.
Cushing’s syndrome is a disease characterized by an excess of cortisol, the hormone of thestress, and serves as an ideal model to analyze the cerebral consequences of chronic hypercortisolemia. It has been described that these patients present depression in more than half of the cases, premature cortical atrophy and cognitive alterations, mainly of memory and learning.
Stefania Schiavone and her collaborators have recently published a work in Antioxidants & Redox Signaling where they highlight that prolonged severe life stress, such as that which occurs in wars, divorces or child abuse, is accompanied by oxidative stress at the nervous system level. The authors describe studies that, using brain imaging techniques, have seen significant changes in neurons in the prefrontal cortex, basal ganglia, insula, and anterior cingulate of victims of early physical or sexual abuse, with a reduction in brain volume of between 10 and 40%. This type of stress has also been linked to the subsequent development of pathologies such as post-traumatic stress disorder, major depression and schizophrenia .
In any case, the style of coping with the problems that each person has is considered as a relevant factor that modulates the effects of stress and is postulated as a way of intervention in the prevention of associated diseases.
Marisa Fernández, Senior Neuropsychologist, Unobrain
