Moderate exercise even for 20-30 minutes is enough to stave off depression. Researchers from the University of Toronto carried out the first longitudinal review to focus exclusively on the role that exercise plays in maintaining good mental health and preventing the onset of depression later in life. PhD candidate George Mammen's review was supervised by Professor Guy Faulkner a co-author of the research. The review analysed over 26 years' worth of research findings to discover that even low levels of physical activity (walking and gardening for 20-30 minutes a day) can ward off depression in people of all age groups.