Nature Prescriptions Cut Loneliness, and Insurers May Be Next

Loneliness scores among 320 adults in low-income Barcelona neighborhoods fell 16.8% a year after a nature-based social prescription. The drop held through 12 months. Health-related quality of life did not move.

That split is now the pitch to health systems. A clinic can send a lonely patient to a garden group or hand over a list of parks, watch the loneliness score fall, and still miss the quality-of-life gain insurers usually want. Modelers have started turning the same trial into extra years of life, and the U.S. scientist who led the work wants American insurers to pay for community garden memberships.

Two Paths, Same Parks, 320 Adults

Jill Litt, professor of environmental health at the University of Colorado Boulder and principal investigator of the RECETAS consortium, has argued for years that nature prescriptions had passion and little proof. The Barcelona results, published in the October issue of The Lancet Regional Health Europe, are the proof she wanted.

Researchers screened 411 adults who said they suffered from loneliness in 12 low-income neighborhoods of the Barcelona metro area, then randomized 320 of them, 160 to each arm, between January 10, 2023, and June 11, 2024. Eighty percent were women. The median age was 62.8. The work is the observer-blinded trial of 320 adults registered as NCT05488496.

Half joined Friends in Nature, a nine-week program of two-hour weekly sessions in groups of eight to 10, with two trained facilitators. The outings came from a neighborhood menu: gardens, parks, riverways, coast, birdwatching, and art made from natural materials. The other half got a 30-minute motivational interview and the same free menu to use on their own.

THE TWO ARMS IN BARCELONA

Laura Coll-Planas, first author and a researcher at the University of Vic, described the group arm as three jobs at once: peer support, social time strengthened by being outdoors, and a chance to practice social skills. Early dropouts were lower in the groups (14% versus 28%, p=0.002). One person in the group arm had an adverse event.

Loneliness Scores Kept Falling After the Groups Ended

Loneliness was scored on the 11-item De Jong Gierveld scale. Across both arms, scores fell an average of 10.5% at three months, the trial’s primary checkpoint, a mean change of -0.73 points (95% CI -1.04 to -0.42). The decline continued: 12.3% at six months and 16.8% at one year.

The two arms did not differ enough at three months to rule out chance. The gap was 0.30 points (95% CI -0.26 to 0.86, p=0.296). For many people, a conversation and a list of nearby green places did the same work as nine weeks of facilitated groups.

The groups pulled ahead only for people who started lonelier and in worse emotional shape, a moderation finding at p=0.003. People who arrived less lonely and steadier did as well with signposting. Litt said the effects were sustained, and that many participants still meet for outdoor activities.

FROM GRANT TO FOLLOW-UP

1. March 2021: RECETAS starts, funded by a €5 million Horizon 2020 grant, with 13 institutions in nine countries.
2. January 10, 2023, to June 11, 2024: Barcelona recruitment runs in 12 low-income neighborhoods.
3. August 2026: The Barcelona trial appears in The Lancet Regional Health Europe.
4. October 8, 2026: A lifetime model built on the same trial estimates extra years of life and extra years without loneliness.

Litt has heard patients describe loneliness as a knot in the stomach. She defines it as a subjective gap between the relationships people expect and the ones they have. “You could be in a room full of people and still feel lonely,” she said.

Quality of Life Did Not Move

The trial’s other co-primary outcome was health-related quality of life on the 15D instrument. Neither arm improved. That is the result health systems will have to live with if they treat a lower loneliness score as a clinical win.

The Barcelona sample was mostly women around retirement age, which the authors say limits how far the finding travels to men and to younger adults. Everyone in the study received some form of nature referral, because the team judged a no-support control unethical. Participants and facilitators knew which arm they were in.

A parallel RECETAS trial in Helsinki, run with frail older adults in assisted-living homes, produced a different pattern. There the Friends in Nature groups cut loneliness more than usual care and improved several quality-of-life dimensions. About 55% of residents in the screened Helsinki homes felt lonely at least sometimes. Same program, two cities, two answers.

Louise Chawla, an environmental psychologist and professor emerita at CU Boulder, said nature stores a calm people can recall later. “It’s not just restorative when you are in a place but also when you go back to it in memory,” she said. She wants group healing in parks and community gardens, because one-to-one therapy cannot meet the demand.

Clinics Already Pay for People Who Feel Alone

The World Health Organization’s Commission on Social Connection estimated that one in six people worldwide feel lonely and that there are 871,000 deaths linked to loneliness each year, about 100 an hour. In Spain, about 20% of people report loneliness. ISGlobal, the Barcelona institute that led the trial, puts the city count at about 100,000.

In the United States, a January 2024 American Psychiatric Association poll of 2,200 adults found that 30% felt lonely at least once a week over the prior year, and 10% felt lonely every day. The 2023 advisory on social connection, issued when Vivek Murthy was U.S. surgeon general, tied poor connection to a 29% higher risk of heart disease, a 32% higher risk of stroke, and a 50% higher risk of dementia in older adults, and compared the mortality hit to smoking 15 cigarettes a day.

WHAT LONELINESS ALREADY COSTS CARE

• Medicare extra spend: Social isolation among older adults accounted for an estimated $6.7 billion a year in extra U.S. Medicare costs, largely from hospital and nursing-facility bills, in the 2023 advisory.
• Employer absenteeism: The same advisory put stress-related absenteeism tied to loneliness at $154 billion a year for U.S. employers.
• Clinic load: People who are lonely visit doctors more often, Litt said, sometimes in search of human contact, and they show up in emergency departments on Friday afternoons with vague complaints.
• Stigma: Patients often do not name loneliness and treat the physical symptoms as something else, so the clinic keeps running tests a park outing will not replace.

Litt, who also works with ISGlobal, said that once clinicians dig into those visits they find loneliness underneath, and that the fix may sit outside the medical system. The second-order bet is that a nature referral can pull some of those visits off the clinic floor and onto a city’s parks budget.

Britain Built the Referral Desk Spain Is Using

Social prescribing is already ordinary in parts of Europe. A trusted clinician flags a non-medical need and points the person to a choir, a walking group, or a volunteer shift. Nature-based social prescribing adds parks, gardens, and outdoor groups to that list.

University College London research, cited by the National Academy for Social Prescribing, counted 5.5 million general-practice referrals to social prescribing in England since 2019, including more than 1 million in 2023. An academy estimate put a £9 wellbeing return on each £1 invested, based on life-satisfaction scores. A separate academy figure put National Health Service savings at about £4 for each £1 spent on link-worker salaries, before training and onward referral costs.

Those returns come from mixed evaluations, some without tight controls, and they are not the Barcelona trial. What they show is a health service that already treats community groups as part of care. Catalonia’s public health agency posted the RECETAS-BCN results as evidence that both a facilitated group and a lighter community referral can cut loneliness in poor urban neighborhoods.

RECETAS is a six-city nature prescribing project that began in March 2021. Random trials ran in Barcelona, Prague, and Helsinki. Observational studies ran in Marseille, Cuenca in Ecuador, and Melbourne. Litt has said the program reached about 1,200 adults across those sites.

WHERE RECETAS TESTED THE MODEL

• Barcelona: Adults 18 and older in 12 low-income neighborhoods; both arms cut loneliness; quality of life unchanged.
• Helsinki: Frail older adults in assisted living; groups beat usual care on loneliness and improved some quality-of-life scores.
• Prague: Community-dwelling adults over 60, a third random trial under the same protocol.
• Marseille, Cuenca, Melbourne: Quasi-experimental sites, built to test whether the idea travels outside a random-trial frame.

On X, the conversation around the paper has been thin and professional. Gil Penalosa, the urbanist behind 8 80 Cities, treated the result as a city-design finding: facilitator-led groups in poor neighborhoods, parks as health kit. Patient forums have not taken it up. The argument is among people who run parks and clinics, which is the tell. The product being sold is a referral pathway, not a new drug.

Can U.S. Insurers Cover a Community Garden?

U.S. doctors can already write a park prescription. They cannot yet bill an insurer for a garden club. Litt is trying to close that gap with American trials, hoping coverage might one day include a community garden membership or a birdwatching club.

Park Rx America, launched around 2016 by Dr. Robert Zarr, gives clinicians a protocol for dose, place, and activity, then sends patients reminders. Stacy Beller Stryer, the group’s associate medical director, said nearly 2,000 providers have registered across the United States and other countries and have issued more than 7,000 nature prescriptions since 2019. She put the number of similar U.S. groups at about 100. Palm Beach County, Maricopa County, and Santa Clara Valley clinics run local versions that point patients to trails, yoga in the park, and community gardens.

That is not insurance. The scripts are free advice attached to public land. Litt’s line is that cities already spend on green infrastructure and now need a bridge to health systems. “There has been a lot of passion about nature-based prescriptions, but not a lot of evidence,” she said. “We now have randomized controlled trials showing this works and the impacts last.”

Some participants told her nature does not judge, and that it is hard to be angry outdoors. “Nature creates a safe space to support the formation of social bonds,” Litt said. An ISGlobal post quoting her put the claim in harder words: nature works much better than any pill. The Barcelona data support a narrower sentence. Nature, with a list or with a group, lowered a loneliness score. It did not raise quality of life, and for many people the list was enough.

Modelers Now Count Extra Years From a Garden Group

On October 8, 2026, a team at UMIT TIROL in Austria, with Litt and Coll-Planas among the co-authors, published a lifetime Markov model that stretches the 12-month Barcelona follow-up across remaining life. It is not a cost study. It converts loneliness into disease risk and counts years.

The model starts a Spanish cohort at mean age 61, 80% women, in a lonely-and-well state, then lets people move into reduced loneliness, relapse, or loneliness-linked illness (depression and anxiety, type 2 diabetes, dementia, cardiovascular disease) and death. A two-point drop on the De Jong Gierveld scale counted as success. On that scale, a score of three to 11 still counts as lonely, so “reduced” does not mean cured.

LIFETIME OUTCOMES FROM THE BARCELONA ARMS

Those lifetime gains of 0.39 QALYs and 2.62 loneliness-free years held in most sensitivity runs. In probabilistic analysis, the group program was the better strategy in 89% of simulations. The results moved most when the modelers changed assumptions about how well the program still worked between six and 12 months, how often loneliness returned, and how much loneliness raises the risk of dying.

The paper’s own close is the constraint on Litt’s insurer pitch. Further research, including a cost-effectiveness analysis, is still needed, the authors wrote, before health systems can be sure the groups are worth buying. The model gives years. It does not give a price.

We have nature in our cities and investment in our green infrastructure. Now we need a mechanism to bridge these resources with our health systems.

Jill Litt, professor of environmental health, University of Colorado Boulder

Spain can fold a garden group into a public health pathway that already refers people to community assets. The United States can write a park script today and still leave the patient to find the bus fare. Until a U.S. trial reports, and until someone prices the groups against the $6.7 billion isolation already bills to Medicare, the Barcelona 16.8% remains a lasting score change in one city, not a covered benefit.

Disclaimer: This article is news reporting and analysis of published research on nature-based social prescribing and loneliness. It is informational only and is not medical advice, a diagnosis, a treatment plan, or a recommendation to start, stop, or change any therapy or outdoor program. Readers who are considering a nature group, a park prescription, or any change in care for loneliness, depression, anxiety, or related conditions should consult a licensed physician, psychologist, or other qualified clinician who knows their history. Figures, trial results, and program statuses reflect the papers, registries, and public-health statements cited here and may change as further RECETAS sites, U.S. trials, and cost studies report.