This is the 2007 version. Click here for the 2017 chapter 14 table of contents.

Stress

Stress is the response of an organism to novel or threatening situations that are unpleasant in character. In the 1930s physiologist Walter Cannon described how the sympathetic nervous system reacts to threatening situations. According to Cannon, a chemical called "sympathin" made the organism ready to run away or fight. Here is a list of symptoms reported by fighter pilots during World War II from the stress of aerial combat.


Stress symptoms reported by pilots

"Sympathin" is what we now call adrenaline or epinephrine. When released into the bloodstream and nervous system, it provokes a general activation of the sympathetic division of the autonomic nervous system, the fight or flight reaction (see p.71). We are all familiar with the effects of adrenaline. The heart beats faster, a person may perspire more, fatigue and tiredness vanishes, muscular activity becomes easier, and reactions become quicker. Over the short term, this is an adaptive response that may help an organism survive. However, if the reaction continues too long, it can take a toll on the organism.

How does the effect of stimulant drugs relate to stress?

The effects of stress are duplicated almost exactly by stimulants such as amphetamines ("speed") and cocaine (Antelman and colleagues, 1980). Both stress and stimulant drugs produce heavy releases of corticosterones, the "stress hormones." Both stress and stimulant drugs increase heart rate and other signs of activity in the sympathetic nervous system. They cause animals to engage in repetitive, stereotyped activity.

Eventually this high level of activation leads to "burn-out" and paranoid psychosis: delusions of persecution, agitation, and hallucinations. MacLennan and Maier (1983) offer a variety of evidence suggesting that stress can mimic the effects of amphetamine or cocaine. For example, a stressful life event can re-awaken a paranoid psychosis in a former amphetamine addict who now abstains from the drug.


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