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body reacts to stress by secreting neurochemicals: when secreted into the bloodstream they
are called hormones; when secreted into the synapse between neurons they are called
neurotransmitters. The same chemicals can serve both functions. It is known that
the nervous system of opiate addicts is hypersensitive to chemically induced stress, and
there is evidence that they are more sensitive to emotional stress than non-addicts.1
What is unclear is whether this hypersensitivity existed before initial drug
use, rendering the individual more vulnerable to the drug, or resulted from the
effects of chronic drug abuse on the brain.
A primary reason for the stress-reducing attribute of opiates is that they inhibit the
release of stress hormones by the hypothalamus and pituitary. During
withdrawal from opiates the level of stress hormones rise, and stress-related
neurotransmitters are released in brain. These chemicals trigger emotions that the
addict perceives as highly unpleasant which motivates drug seeking behavior.
Because the effects of most opiates and related drugs last only a few hours,
opiate addicts experience withdrawal several times per day. The continuous switching
on and off of the neurochemical stress system exacerbates whatever hypersensitivity the
person originally had. As a result the stress system of the addict is on hair
trigger release. Now, even minor provocations may produce a surge of stress
related neurochemicals and the consequent emotional reaction. Addicts who are
heroin-free and methadone free overreact to stressors, but addicts on methadone react
normally. Methadone is long acting - 24 hours vs. 4-6 hrs - and so the addict
does not experience withdrawal on a daily basis. Without the constant activation
involved in these withdrawals, the brain's stress system appears to normalize.
Cocaine and stimulants also heighten the body's sensitivity
to stress, but in a different way. For example, when a cocaine user takes cocaine,
the stress systems are activated much like when an opiate user goes into withdrawal, but
on cocaine the person perceives this as part of the cocaine rush because the drug is also
stimulating parts of the brain involved in reward. When the acute effects ware off, the
stress systems are activated - again much like when an opiate addict goes into
withdrawal. This time the cocaine user perceives the activation as unpleasant
because the pleasure circuits are no longer being stimulated. Because stimulants
such as cocaine activate the stress system both when initially consumed and again during
withdrawal, the stress system becomes hypersensitive quite rapidly - often before the user
fully appreciates the change that has taken place.
Footnotes:
1. S. Stocker [1999] Studies link stress and drug addiction. NIDA Notes,
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