Brain's natural reward system begins to normalize a few months into recovery from opioid addiction

A few months into recovery, patients who have successfully stopped taking prescription opioids show signs that their brains' natural reward systems are starting to normalize, according to a new study published in the .

The researchers assessed changes in the brain's reward system in patients who were in residential treatment for their addiction to opioid pain medications.

One group had recently gone through medically assisted opioid withdrawal within the previous one to two weeks. The second group had been drug-free for two to three months. A group of normal controls were also involved for comparison.

After drug withdrawal, many people with opioid addiction experience persistent changes in the reward and memory circuits. For example, they may experience heightened "rewards" or "pleasure" in response to drugs and related stimuli, but greatly reduced responses to naturally pleasurable stimuli (such as good food, or friendship).

"This is thought to occur because opiates are potent stimulators of the brain's reward system; over time, the brain adapts to the high level of stimulation provided by opiates, and naturally rewarding stimuli can't measure up," said Scott C. Bunce, Ph.D., of Pennsylvania State University College of Medicine.

Such strong dysregulation of the natural reward system may be a major factor in the high risk of relapse during recovery.

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 The recently withdrawn group also suffered from sleep disturbances, while sleep in the extended care group was similar to controls.

All of these changes correlated with abstinence time. The longer the patient went without using drugs, the lower the abnormal responses.

"It shows that if the patient remains in treatment and off drugs for several months, the body's natural reward systems may have the capacity to return toward normal, making it easier for them to remain drug-free outside the treatment setting," said Bunce.

With continued research, testing the patients' natural reward systems might help evaluate how their recovery is proceeding.

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