Using greenspace and nature exposure as an adjunctive treatment for opioid and substance use disorders: Preliminary evidence and potential mechanisms.

The demand for opioid medication to effectively treat pain has contributed to the surging opioid crisis, which is a major source of morbidity and mortality in the U.S. More than 100,000 people begin opioid maintenance treatment (OMT) annually, the standard pharmacotherapy for opioid use disorder (OUD). Although OMT is the standard care for OUD, patients often experience or develop a heightened sensitivity to pain (hyperalgesia) as a result of the opioid medication, and also have high rates of stress, affective, and anxiety-related conditions. These conditions are interactive with other behavioral and environmental correlates of opioid and other substance use disorders including impulsive decision-making (e.g., harmful opioid use associated with increased delay discounting), and a lack of alternative (i.e., substance-free) and social reinforcement. Collectively these complex and multifaceted factors constitute significant predictors of lack of adherence to OMT (and other pharmacotherapies) and relapse. There is an urgent need, therefore, to develop novel adjunctive treatments that preserve the benefits of OMT and various pharmacotherapies, and simultaneously diminish continued pain and hyperalgesia, reduce stress and anxiety-related conditions, target relevant behavioral mechanism such as impulsive choice, and also serve to enhance the value of alternative and substance free activities. Here, we discuss evidence that an environmental manipulation - access to greenspace and nature - could serve as a potential adjunctive treatment to standard pharmacotherapies by targeting multiple biological and behavioral mechanisms that standard pharmacotherapies do not address.