Beginners Guide: Neuroscience of Opioid Addiction
In February, President Obama proposed a FY17 budget that allocates $1.1B in new funding to address the opioid use disorder crisis in the United States. Whatever one’s politics (or general anxieties about the 2016 election season), we all agree that something must change. Despite the best efforts of policymakers, health care professionals, and communities to combat this problem, opioid deaths continue to rise, prompting the question: Why is the epidemic so pervasive?
There are many reasons – historical, socioeconomic, biological – but understanding the neurological basis of opioid addiction helps explain its complexity and prevalence. Importantly, understanding the brain changes that accompany opioid addiction will also help us combat the stigma associated with drug use, and treat these individuals based on what the evidence reveals as most effective.
How does addiction begin?
Opioids stimulate a structure in our brain called the mesolimbic reward system in the ventral tegmental area, or VTA (what a mouthful). The VTA system is responsible for the release of a chemical called dopamine (DA). Dopamine production drives many of the pleasurable sensations in life, such as those associated with food and sex. Opioids, in essence, stimulate our brains’ “reward system,” driving a compulsion to take the drug again and again.
The brain changes that accompany addiction, however, are complex, pervasive, and last much longer, according to many neuroscientists, who are still uncovering the full extent of these effects.
Over time, however, the opioid receptors in the VTA become less sensitive to opioid stimulation; we need to use more opioids to achieve the same amount of pleasure. Another involved brain area is the locus ceruleus (LC), which regulates such feelings as wakefulness and energy. Opioids suppress the activity of neurons in the LC, causing many of the feelings associated with an opioid high. Unfortunately, over time, this process also causes the same neurons to become hyperactive in the absence of opioids, causing jitters, dizziness, and other painful withdrawal symptoms.
Long-term changes in the brain
The brain changes that produce withdrawal are well understood, and often these abnormalities resolve within weeks after detoxification. The brain changes that accompany addiction, however, are complex, pervasive, and last much longer, according to many neuroscientists, who are still uncovering the full extent of these effects.
One of the most meaningful ideas in addiction science is the concept of the “changed set point.” Some scientists suggest that the dopamine-producing neurons in the VTA have an original “set point” at which they produce DA when we enjoy our favorite activities. Long-term opioid use disorders alter this set point, so that DA production is reduced during once-loved activities. Eating, riding a bike, watching a movie – all of these may fail to bring the same level of pleasure experienced before addiction begins. This insight illuminates how difficult it can be for individuals addicted to opioids to motivate themselves to resist the drug, attend therapy, or even get out of bed without it.
Importance of MAT and therapy
Addiction’s persistence underscores the importance of a holistic, chronic disease model of care to treat this population effectively (Read more about this chronic care model in our white paper, “Confronting the Crisis of Opioid Addiction” and an earlier blog post). Key elements of this evidence-based model include medication-assisted treatment (MAT) and therapy.
Pharmacotherapies for opioid addiction – such as methadone and suboxone – help counteract many of the brain changes that take place during addiction. The medications bind to the same neuronal receptors that opioids do, thereby helping to reduce cravings, demotivation, and other feelings associated with addiction. While not the right choice for every patient, MAT is a powerful tool that can help us improve treatment.
References and further reading:
Kosten TR, George TP. The Neurobiology of Opioid Dependence: Implications for Treatment. Science & Practice Perspectives. 2002;1(1):13-20. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2851054/
Koob GF, LeMoal M. Drug addiction, dysregulation of reward, and allostasis. Neuropsychopharmacology. 2001;24(2):97–129. http://www.nature.com/npp/journal/v24/n2/full/1395603a.html