http://goo.gl/CA6CNj
The test results revealed several significant differences in the brain’s reward system between the groups. Patients in recent drug withdrawal had reduced pleasure responses to “natural reward” stimuli — for example, pictures of appetizing foods or people having fun.
Instead, they had heightened responses to drug-related cues, such as pictures of pills. In the extended-care patients, however, the heightened responses to drug cues were greatly reduced.
Patients in recent withdrawal also had high levels of the stress hormone cortisol. In those who had been drug-free for a few months, cortisol levels were somewhat reduced, although not quite as low as in healthy controls. The recently withdrawn group also suffered from sleep disturbances, while sleep in the extended care group was similar to controls.