A 2-SEPARATE-MOTIVATIONAL-SYSTEMS HYPOTHESIS OF OPIOID ADDICTION

There has been a long debate as to whether opioids are sought for with drawal relief or for their ability to serve as incentives in their own right. We suggest that independent motivational systems mediate the r ewarding effects of opioids in the nondependent state and in the physi cally dependent/withdrawal state. In the opioid-dependent state and th e presence of opioid withdrawal. the rewarding effects of withdrawal r elief inhibit or mask the acute rewarding effects initially exerted in the nondependent state, but the acute rewarding effects are unmasked after the alleviation of withdrawal. (C) 1998 Elsevier Science Inc.