Injury, Infection, and Recovery from Opioid Use Disorders in Michigan

Abstract

The opioid crisis is an ongoing serious public health challenge in the United States. Starting in the late 1990s, increases in prescriptions for opioid pharmaceuticals led to increases in nonmedical prescription opioid use and, in some cases, subsequent heroin use. These changes have had significant impacts on public health. Drug overdose mortality quadrupled between 1999 and 2016 and increases in injection drug use have led to a rise in bloodborne viral infections. Improving substance use disorder treatment outcomes is a major public health priority; 40-60% treated for a substance use disorder relapse within a year of completing treatment.

This dissertation explored three public health priorities related to the opioid crisis: injury, infection, and recovery. In chapter 2, we focused on injury prevention by examining overdose experiences, naloxone knowledge, attitudes towards overdose risk, and justice involvement among a sample of adults who used opioids in a justice diversion addiction treatment program in Michigan. We used latent class analysis to identify two general justice involvement patterns that occurred prior to treatment: the first was characterized by many recent arrests and little incarceration time, and the second involved incarceration prior to diversion. Only 56.2% of participants had heard of naloxone and identified it as an overdose treatment, yet 68.1% had experienced and 79.2% had witnessed an overdose. These results highlighted the universal need for overdose education and naloxone distribution in the justice diversion addiction treatment setting.

In chapter 3, we characterized the potential impact of interventions to combat the growing incidence of hepatitis C virus (HCV) infection among young people who inject drugs (PWID). We developed an age-stratified ordinary differential equation HCV transmission model fit to surveillance data from Michigan. We predicted that treating 10% of PWID per year in Michigan could reduce HCV cases by over half. Coupling HCV treatment with behavioral interventions could further reduce HCV incidence and prevalence.

In chapter 4, we explored a potential new target for adjunctive treatments to promote recovery from opioid use disorders by examining how substance use impacts the gut microbiota. The gut microbiota is the community of living bacteria in the human gut. It is increasingly recognized as an important communicator along the gut-brain axis, the crosstalk pathways between the gut and brain, and may also modify psychopathology. We studied 46 patients receiving outpatient addiction treatment in Michigan who were exposed to opioid agonists (prescription opioids and heroin) and antagonists (naltrexone or naloxone). We found that opioid agonist exposure tended to decrease bacterial community diversity and was associated with lower abundance of Roseburia, a butyrate producer, and Bilophila, a microbe important in bile acid metabolism. We did not find these changes in participants who were concurrently or singly exposed to opioid antagonists. These findings were consistent with those from murine models of morphine exposure and highlighted directions for future work that further explores whether psycho-adjunctive treatments that promote gut health could improve opioid use disorder treatment outcomes.

In chapter 5, I close by highlighting some of the lessons I learned through my dissertation work, and propose new research avenues within the areas of injury, infection, and recovery, that focus on mitigating the negative impacts of the opioid crisis on public health.