Stress, that is, the state of threatened or perceived as threatened
homeostasis, is associated with activation of the stress system, mainly
comprised by the hypothalamic-pituitary-adrenal axis and the
arousal/sympathetic nervous systems. The stress system normally
functions in a circadian manner and interacts with other systems to
regulate a variety of behavioral, endocrine, metabolic, immune, and
cardiovascular functions. However, the experience of acute intense
physical or emotional stress, as well as of chronic stress, may lead to
the development of or may exacerbate several psychologic and somatic
conditions, including anxiety disorders, depression, obesity, and the
metabolic syndrome. In chronically stressed individuals, both behavioral
and neuroendocrine mechanisms promote obesity and metabolic
abnormalities: unhealthy lifestyles in conjunction with dysregulation of
the stress system and increased secretion of cortisol, catecholamines,
and interleukin-6, with concurrently elevated insulin concentrations,
lead to development of central obesity, insulin resistance, and the
metabolic syndrome. Fetal life, childhood, and adolescence are
particularly vulnerable periods of life to the effects of intense acute
or chronic stress. Similarly, these life stages are crucial for the
later development of behavioral, metabolic, and immune abnormalities.
Developing brain structures and functions related to stress regulation,
such as the amygdala, the hippocampus, and the mesocorticolimbic system,
are more vulnerable to the effects of stress compared with mature
structures in adults. Moreover, chronic alterations in cortisol
secretion in children may affect the timing of puberty, final stature,
and body composition, as well as cause early-onset obesity, metabolic
syndrome, and type 2 diabetes mellitus. The understanding of stress
mechanisms leading to metabolic abnormalities in early life may lead to
more effective prevention and intervention strategies of obesity-related
health problems. (C) 2012 Elsevier Inc. All rights reserved