Contact with nature as drug treatment : the effects of contact with nature on psycho-physiological symptoms of people with drug use disorder

Abstract

Drug use disorder is a chronic disease characterized by a problematic pattern of use of a drug or drugs, impairing the drug users’ psycho-physiological systems. Although it is well established that contact with nature provides many human health benefits, as measured through psycho-physiological responses, few studies focus on how nature impacts people with drug use disorder. We do not know the extent to which contact with nature impacts drug users’ psycho-physiological responses. The key research question is: to what extent does contact with nature impact people with drug use disorder, as measured through multiple psycho-physiological indicators? In the first study, I examine the impacts of exposure to nature on drug users’ stress levels and identify the dose-response curve describing the relationship between nature density and stress reduction. I conducted a panoramic photo-based experiment with 660 drug users at four compulsory drug treatment centers. This study analyzed ten groups of photos with varied tree canopy density, including nine treatment groups (density: 4.2%-62.0%) and one control group (density: 1.7%). I measured participants’ self-reported stress levels of control and treatment groups. In the second and third studies, I investigate the impacts of eight-week contact with nature on drug users’ physiological and psychological symptoms. I conducted an eight-week randomized controlled field experiment with 65 drug users in a community drug rehabilitation program. The participants in the nature group participated in a one-hour natural intervention every week for eight weeks, while the participants in the control group did not join the nature intervention. Study 2 explores participants’ physiological responses, as measured through salivary cortisol and secretory Immunoglobulin A (sIgA) levels, while Study 3 explores participants’ s psychological responses, as measured through self-reported drug craving, stress, and rumination levels. Findings of Study 1 suggest that street scenes with trees, compared to barren streets, were significantly associated with reductions in drug users’ stress levels. When tree cover density increased from 4.2% to 36.8%, the relationship between tree canopy density and stress reduction was positive and linear. Beyond 36.8%, the relationship flatlined. The dose-response curve can be described as a “positive slope-plateau” curve. Findings of Study 2 suggest that eight-week and regular nature contact significantly reduced cortisol levels and marginally significantly increased sIgA levels. Findings of Study 3 suggest that eight-week and regular nature contact significantly reduced drug craving, stress, and rumination levels. In sum, the findings suggest that contact with nature may be an effective adjunctive treatment for alleviating drug use disorder, primarily by decreasing drug users’ brain stress system activity, drug craving, stress, and rumination levels, and secondarily by enhancing immune functioning. To my knowledge, this work is the first to identify the benefits of contact with nature on drug users’ psycho-physiological responses, thereby potentially diminishing drug use disorder, which may be of significant interest to policymakers, healthcare professionals, and urban planners and designers.