Clinical Trial Examines Nature-Based Social Prescribing for Urban Adults Experiencing Loneliness

A randomized controlled trial conducted in Barcelona, Spain, has investigated the effects of nature-based social prescribing on loneliness and health-related quality of life among vulnerable urban adults. Published in The Lancet Regional Health – Europe, the study evaluated whether guided outdoor group gatherings or a lighter-touch signposting approach could better address social and emotional isolation. The research provides preliminary insights into how healthcare systems might connect individuals with community and environmental resources, though experts emphasize the need for further controlled investigations.

Understanding the Scope of Social Isolation

Loneliness is defined as a subjective and distressing experience that arises when an individual’s social relationships fall short of their personal needs or expectations regarding quality or quantity. Public health organizations recognize it as a significant concern, particularly among populations facing socioeconomic disadvantages. In Spain, approximately one in five residents report feeling lonely, with numbers in metropolitan Barcelona nearly doubling over recent years. Social prescribing has emerged as a potential strategy, allowing health professionals to link patients to community-based activities rather than relying solely on clinical treatments. Nature-based social prescribing specifically connects individuals to outdoor activities in natural settings, under the premise that environmental contact fosters belonging and social cohesion.

Trial Design and Participant Characteristics

Led by the RECETAS Project, the observer-blinded trial involved 320 adult participants recruited from 12 socioeconomically disadvantaged neighborhoods in Barcelona. Eligible individuals reported experiencing loneliness ranging from occasional to constant. Participants with severe illnesses, major disabilities, or specific mental health conditions that would hinder group participation were excluded. The cohort was predominantly female, with a median age of approximately 63 years. Individuals were randomly assigned to one of two study arms:

• Intervention Arm: Participants joined groups of eight to ten people meeting weekly for nine weeks, guided by trained facilitators. Sessions integrated group exercises with outdoor excursions to parks, riverbanks, and gardens chosen from local co-created menus.
• Active-Control Arm: Participants received a brief motivational interview and were given the same menus of local nature activities to pursue independently through active signposting.

Researchers measured outcomes at baseline and at three, six, and twelve months, using the De Jong Gierveld loneliness scale and the 15D health-related quality of life questionnaire. Blinded investigators conducted all assessments and statistical analyses.

Findings on Loneliness and Quality of Life

Across the entire study sample, model-estimated loneliness dropped by an average of 0.73 points at the three-month primary endpoint, representing a reduction of roughly 10.5 percent from baseline. This decline appeared to continue over subsequent evaluations, reaching about 12 percent at six months and nearly 17 percent at twelve months. However, the difference between the two study arms at three months was small and not statistically significant, indicating that the facilitated group program did not outperform the independent active signposting approach overall. Because the trial lacked an inactive or passive control group, investigators noted that the observed declines cannot be definitively attributed to the interventions alone, as they might reflect regression to the mean or participation effects. Furthermore, scores on the health-related quality of life questionnaire did not change significantly across the sample during the study period, a result authors attributed partly to a ceiling effect where baseline scores were already near maximum levels on several items.

Exploratory Insights and Study Limitations

An exploratory post hoc analysis suggested that a participant’s initial emotional wellbeing might influence which intervention format is more beneficial. Individuals with lower baseline emotional wellbeing scores appeared to experience greater relative benefits from the facilitated group program, whereas those with higher emotional wellbeing achieved comparable or slightly better loneliness outcomes with the independent active signposting approach. The authors caution that these moderation findings are preliminary and require prospective confirmation in future trials. The study also faced limitations, including a high dropout rate—particularly in the control arm due to participant disappointment regarding random assignment—and a reliance on a single direct screening question for loneliness. Researchers emphasized that programs should be carefully matched to individual preferences and needs rather than applied uniformly.