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The Neurobiology of Addiction


This month the Colorado state legislature is considering expanding an effort by the CU College of Nursing to develop new treatment options for opioid use disorders in rural areas of the state. The College's program was featured in a January 4th article in the Denver Post, and also last week in a piece on health care innovations by Colorado Public Radio.

Addiction is perhaps the classic example of Intuitive-System processes overriding Narrative-System ones. But the intractable problems associated with drug use involve both mental systems. The hallmarks of drug addiction are physiological phenomena: tolerance (needing more of a drug to get the same effect) and withdrawal (iatrogenic symptoms caused by the lack of a drug when it leaves the body). Together, these processes produce a subjective experience of craving in which the person has a very strong desire for the drug, a desire that may be experienced as outside of one's own control. In fact, recent research shows that craving is linked to increased activity in the basal ganglia and amygdala -- Intuitive-System centers of the brain -- and reduced activity in Narrative-System centers linked to the prefrontal cortex. This is just what we might expect to see when a decision is made based on Intuitive-level factors with little Narrative-system input, and it fits well with people's subjective report that they sometimes feel their brain and body have been "hijacked" by addiction, producing behaviors that they consciously wished to avoid. Although opioids have their primary therapeutic effects by binding with pain receptors, the Intuitive-system factors are more strongly linked to the brain's dopamine system. In fact, opioid withdrawal also strongly reduces dopamine production in the areas of the brain connected most strongly to Intuitive-level decision making.

The difference between procedural memory ("knowing how") and declarative memory ("knowing that") is perhaps the most fundamental distinction between Intiutive- and Narrative-level thinking. Another line of research shows that memories related to drug use are more strongly encoded in lower-brain areas tied to habit and automatic generation of behavior, and that the effects of the drugs may actively interfere with the typical formation of declarative memories that would mitigate future cravings for the drug. Furthermore, the effects of drugs on the brain may produce lasting changes in cell structure, functioning, and epigenetic expression that favor Intuitive-level decision making in future scenarios involving acquisition and use of the drug. Taken together, these findings suggest not only that Intuitive-level decision-making leads to greater drug use, but that drug use leads to more Intuitive-level decision-making when it comes to future drug use!

Given these complex effects of opioid drugs on immediate decision-making at the Intuitive level and later memory formation at the Narrative level, how can clinicians help? The most current approaches to opioid use disorder are "medication-assisted treatments" (MAT) that combine physiological interventions to address the Intuitive System with behavioral interventions to address the Narrative System. In programs supported by the CU College of Nursing's rural MAT pilot project, for example, all sites are offering medications that provide lower-level activation of opioid receptors while interfering with other opioids' effects (partial opioid agonists like methadone or buprenorphine/Suboxone) or medications that block opioid receptors altogether (opioid antagonists like naltrexone/Vivitrol). These treatments are intended to reduce cravings and interrupt the physiological reward cycle associated with opioid use. But because these medications don't provide the same level of relief or reward as the original drugs, patients are at high risk for relapse. It is therefore very important to also address the Narrative-System gaps that may be contributing to ongoing drug use, working with people either individually or in psychotherapeutic groups to modify their expectations and beliefs about drug use at the Narrative level.

In the CU College of Nursing project, sites are offering on-site or virtual groups for people with a history of legal system involvement, survivors of trauma, people in rural areas, and others to address their unique histories and to help them craft new narratives in support of abstinence. These Narrative-System changes can help to support long-term abstinence once the Intuitive-level craving for the medication subsides.

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