There is consistent evidence that stress, HPA function, and addictive behaviors are closely interrelated. Studies in rodents have shown that physiological or psychological stressors elevate POMC mRNA levels in the pituitary (8), and chronic antidepressant treatment decrease pituitary levels of POMC mRNA (9). Stress is a common trigger for drug or alcohol use, and individuals experiencing stress (or depression and/or anxiety) are more prone to abuse drugs or alcohol. Consumption of drugs or alcohol can, in turn, alter HPA function, and modulate the production of ACTH, β-endorphin, or glucocorticoid hormones. Cocaine administration activates the opioid system and the HPA axis, and enhances the secretion of β-endorphin, ACTH and corticosterone in rat (10), mouse (11), and human (12). Similarly, acute ethanol administration induces an increase in the release of pituitary β-endorphin (13). In addition, both increased and decreased β-endorphin release has been observed in chronic ethanol treatment (14).
