Understanding 'Cathartic' in Urban Gardening

In the article discussing the rise of urban gardening, the author states: "Many city dwellers have discovered the cathartic benefits of tending to their own gardens, transforming their balconies into lush retreats amidst the concrete jungle. This newfound passion not only offers a respite from the hustle and bustle of city life but also evokes a deep sense of connection to nature amidst the urban sprawl."

In this context, what does the word cathartic most closely mean?