DIFFERENT BRAIN

3/25/2007

The neurobiological consequences of early stress and childhood maltreatment.

Neuroscience and Biobehavioral Reviews 27 (2003) 33-44

Martin H. Teicher, Susan L. Andersen, Ann Polcari, Carl M. Anderson, Carryl P. Navalta, Dennis M. Kim

++++

tel 1-617-855-2970

fax 1-617-855-3712

martin_teicher@hms.harvard.edu (M.H. Teicher)

PROPOSED EVOLUTIONARY HYPOTHESIS

“We also summarize in this article an alternative evolutionary hypothesis in which we propose that early stress signals the nascent brain to develop along an alternative pathway adapting itself to survive and reproduce in a malevolent stress-filled world.  (Teicher/nc/34)”

++++

“What are the functional consequences of stress-related effects on the development of the hippocampus, amygdala, corpus callosum, cerebral cortex and cerebellar vermis?  (Teicher/nc/37)”

++++

“There are also significant sex differences with respect to hormonal influences on development.  We have postulated that limbic electrical irritability stemming from early abuse is a significant predisposing factor for development of BPD and other psychiatric syndromes [2].  Estrogen exerts a substantial epileptogenic effect on limbic structures, particularly when they are already sensitized [183].  Progesterone and its metabolites inhibit kindling and seizure activity [183], but may produce depression 183].  (Teicher/nc/38)”

“Testosterone and dihydrotestosterone exerts antiseizure effects through inhibition of glutaminergic NMDA receptors [183].  Hence, sex-related differences across (Teicher/nc/38) development may yield substantial effects on the neurobiological manifestation of childhood maltreatment.  (Teicher/nc/39)”

++++

“Initially, our view was that early stress evoked a cascade of neurohumoral and neurotransmitter effects that produced enduring deleterious alterations in brain structure and function.  Within this narrow perspective, we viewed excessive stress as simply a toxic agent that interfered with the normal progression of brain development, yielding a somewhat altered and impaired brain [35,36,48,88,184,185].  Further, we postulated that the neuropsychiatric consequences associated with early exposure to stress were due to this form of developmental insult [2,85,184,185].  This point of view has now been articulated by several other authors [12,15,186-198].  (Teicher/nc/39)”

“More recently, we have come to re-evaluate this initial view [1,190].  We postulate instead that these alterations in neurodevelopment represent an adaptive, alternative developmental pathway.  (Teicher/nc/39)”

“Stress-induced developmental modifications, triggered by the nature of experience during critical, sensitive stages, are designed to allow the individual to adapt to high levels of life-long stress or deprivation that may be signaled by early stressful experience.  If an individual is born into a malevolent and stress-filled world, the manifestations of early stressful experience on later development may serve an adaptive purpose, enabling the individual to mobilize intense fight – flight responses or react aggressively to challenge.  On the other hand, these alterations are not optimal for survival and reproductive success in a more benign environment.  (Teicher/nc/39)”

“In short, we propose that the brain goes through a sensitive period in postnatal life in which exposure to high levels of stress hormones select for an alternative pathway of development that occurs through a cascade of neurobiological effects.  That is, exposure to significant stressors during a sensitive developmental period causes the brain to develop along a stress-response pathway.  Further, we hypothesize that exposure to corticosteroids is a crucial factor in organizing the brain to develop in this manner.  Seckl and colleagues [191-193] have also postulated that glucocorticoids exert an organizing effect on development.  They have proposed that late prenatal exposure to glucocorticoids produces low-birth weight infants, and exerts an organizing effect on the hman fetus to produce an enduring elevation in corticosteroids levels accompanied by a substantially increased risk for the development of cardiovascular disease and type-II diabetes.  In our hypothesis, postnatal neglect or other maltreatment serves to elicit a cascade of stress responses that organizes the brain to develop along a specific pathway selected to facilitate reproductive success and survival in a world of deprivation and strife.  This pathway, however, is costly as it is associated with an increased risk of developing serious medical and psychiatric disorders and is unnecessary and maladaptive in a more benign environment.  (Teicher/nc/39)”

“As we stated earlier, the work reviewed here is of a preliminary nature.  These findings require further study and replication.  Future work should widen its focus to the effects of emotional maltreatment and the impact of corporal punishment in addition to abuse.  New imaging techniques, such as diffusion tensor imaging which provides information about white matter structures, will be useful tools in clarifying this area of study.  Finally, an important challenge that remains is the study of the impact of treatment and the potential reversibility of altered neurodevelopment.  (Teicher/nc/39)”

++++