Nature-deficit disorder: Evidence, dosage, and treatment

Claims have long been made of the health-promoting effects of contact with 'nature', but these claims have only recently been subjected to rigorous scientific testing. A strong body of evidence is now in hand. An array of studies ranging from rigorous experiments to large-scale epidemiological work has tied nature to health for outcomes ranging from childhood obesity, to immune functioning and rates of physician-diagnosed disease in adults, to longevity in older adults. Moreover, enough evidence has accumulated to begin to answer key questions about the dosage of nature needed to promote health. Do all forms of nature seem to help? Do small bits of nature help, or is some minimum level required for an effect? Similarly, to what extent is an explicit focus on nature necessary - are effects limited to fishing, hiking, gardening, and the like? The evidence to date suggests, broadly, that total exposure is important; all forms and quantities of exposure are helpful; and the greener the better. From these insights into dosage, nine recommendations are drawn for addressing nature deficits at the population level: green everyday places and views; bring green spaces closer; bring green activities and events closer; make spaces and programs fit nearby users; make green spaces serve multiple activities and uses; support longer visits; reconsider barriers to use; help people start green activities; and help people continue green activities.