Last updated: Thu, Aug 15, 2024
Recent research has shown that the changes in motivation that are seen with chronic pain may be due to causes deep within the brain. Chronic pain causes microglia in the the brain to become activated in areas that are important to reward, mood, and affect. The activated microglia suppress the release of dopamine in an area of the midbrain called the ventral tegmental area. Dopamine is an essential part of the brain's reward circuitry.
This research with mice and rats found that the release of dopamine that is expected when opioids or cocaine were injected into the ventral tegmental area was decreased in the presence of chronic pain. (This suggests that the presence of chronic pain may reduce the risk of addiction in chronic pain patients.) The authors suggest that this same mechanism may contribute to anxiety and depression, which are also found commonly in chronic pain patients.1