Stress generally is defined as any stimulus

Stress generally is defined as any stimulus that challenges physiological homeostasis—that is, which alters the balance or equilibrium of the normal physiologicalstate of the organism. It is important to realize, however, that the term “stress” is rather nonspecific and should alwaysbe qualified. Although all forms ofstress alter homeostasis, they do not all do so in the same manner (i.e.,they have different physiological consequences). Different kinds of stress can stimulate different combinations of signaling molecules (i.e., molecules that aid in cell-to-cell communication, such as neurohormones), thereby producing unique effects on physiological processes. Accordingly, it is imperative to specify the type and duration of stress to which an organism is subjected. Moreover, reactions to a given type of stress vary between individuals, and physiological and behavioral responses tend to be associated with distinct coping styles (Øverli et al. 2007).  Like the susceptibility to AOD use disorders, people’s responses to stress are regulated by the interaction of environmental and genetic factors. In fact, prenatal and early-life stress can have lifelong effects on the body systems involved in the stress response, and these effects may predispose an individual to certain diseases (Maccari et al. 2003). This early programming effect in part is influenced by mechanisms (i.e., epigenetic mechanisms) that alter heritable traits without manifesting as changes in the DNA sequence and which also can aid in the development of AOD use disorders.

The Stress Response

Mammals respond to the various forms of stress with a response comprising at least three components:

·        The glucocorticoid response mediated through a hormone system known as the hypothalamic– pituitary–adrenal (HPA) axis;

·        Activation of the peptide corticotrophin-releasing factor (CRF) outside the hypothalamus; and

·        Activation of one branch of the nervous system (i.e., the sympathetic nervous system) that results in the release of signaling molecules called epinephrine (or adrenaline) and norepinephrine (or noradrenaline).



The glucocorticoid response mediated by the HPA axis involves, as the name implies, three distinct organs.



·        The hypothalamus, a brain region located deep within the brain;

·        The pituitary gland, a small, hormone-secreting gland located directly below the hypothalamus; and

·        The adrenal glands, hormone-producing structures located on top of the kidneys. (Wand 2008, 119–20)



References

Wand, Gary. 2008. “The influence of stress on the transition from drug use to addiction.” Alcohol research & health : the journal of the National Institute on Alcohol Abuse and Alcoholism 31 (2): 119–36.