Plenty of research shows that spending time in nature has powerful health benefits. For people working in cities, that’s not always possible, but there an approximate way to stay positive at least: New research shows that even if you’re trapped in an office or only able to step outside for a moment, small exposures to outdoorsy indicators–seeing trees, the sky, or hearing a birdsong–can boost your mood.

The effect doesn’t disappear once you’ve returned to a cloistered cubicle or apartment: It can last for several hours, with especially strong results for people who suffer from mental disorders.

The study, from King’s College London, was published in the January edition of BioScience. Its proper title: “Urban Mind: Using Smartphone Technologies to Investigate the Impact of Nature on Mental Well-Being in Real Time.” The work was supported by by The Van Alen Institute and Sustainable Society Network+, both of which champion ways to improve city living through better urban design.