____________________________________ Substance Use Disorders: Assessment and Treatment, 2nd Edition
influences the prefrontal cortex so that these activities do not just happen by accident but are provided for and planned. Substances that are capable of creating dependence all activate this circuit, in many instances more powerfully than natural behaviors. This hyperstimulation leads eventually to changes in the neurons in the nucleus accumbens that are experienced as tolerance and craving as well as a compulsion to continue using an intoxicating substance.
harmfulness of abusing the drugs, as the drugs have interfered with the area of the brain charged with this function (Azmitia, 2001). This dynamic is believed to explain the inability of many individuals with SUDs to recognize the severity of their problems resulting from their use of substances—a dynamic referred to as “denial.” The HPA axis is the system responsible for generating stress responses and for the increased production of negative physi- ological stress states that are also associated with addiction and relapse. The HPA axis (Figure 2) includes the hypothala- mus, pituitary gland, adrenal and suprarenal glands, and the neurotransmitter communications among them. The HPA axis helps regulate biological functions such as digestion; mood; temperature; and reactions to stress and trauma such as anxiety, increased heart and breathing rates, increased blood pressure, and muscle strength. Under normal condi- tions, when the amygdala determines that a stress response is appropriate, it activates the HPA neurochemical processes associated with the stress. These processes lead to a cascade of reactions, eventually resulting in the release of the hormone cortisol. Countering this process, gamma aminobutyric acid (GABA) is an inhibitory neurotransmitter that curbs the stress response by suppressing the release of a number of hormones, including cortisol. During withdrawal from alcohol and other addictive drugs, GABA is decreased in the amygdala, allowing increased levels of hormones such as norepinephrine and corti- sol to circulate. This situation accounts for the increased stress
The prefrontal cortex is an area of the brain that mediates responses triggered by the amygdala. This area is responsible for executive cognitive functions—such as comprehension, concentration, cognitive reasoning, planning, and initiation of goal-directed behavior—which are part of human maturation processes. Individuals with a history of addictions have been found to have both loss of volume in the prefrontal cortex and changes in glucose metabolism in the brain, thereby having a reduced capacity to mediate responses triggered by the amyg- dala—responses that are usually stress-induced and impulsive and that have a strong physiological push toward action. This absence of prefrontal cortex mediation of amygdala-driven responses has been implicated in an individual’s vulnerability to craving for substances and the consequent relapse to sub- stance use. Paradoxically, a person abusing substances over a long period of time may fail to have logical awareness about the
BRAIN IMAGE
From Western Schools, 2018.
Figure 1
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