Preventive approach Definition and explanation Clinical examples in for the field of physical activity in the treatment and prevention of depression Universal [45] Strategies that involve the whole population. Provided without screening. Environmental design andmodification (e.g. green space development, walkway modification); cross-governmental initiatives; internet-based promotions; informational programs for the general public [44] Selective [45] Strategies that involve targeted subpopulations whose risk of developing a disorder is above average. Involves identified exposure to specific risk factors.  Risk factors for depression [69,88,89] : Pre-existing disease: e.g. psychiatric illness (e.g. anxiety disorder, age-related cognitive dysfunction, substance-related disorders); general medical conditions (e.g. cardiovascular disease, obesity, diabetes) Health related behaviors: e.g. psychological stress; physical inactivity; alcohol, tobacco and other drugs; sleep disruption; dietary factors. Biological factors: e.g. interferon therapy; pro-inflammatory conditions; S/S 5-HTTLPR genotype Indicated [45] Strategies aimed at subjects who have early and sub-threshold symptoms and signs of illness. Involves a screening process. Sub-threshold depression; early intervention. Primary [46] Strategies to avoid occurrence of disease. As per universal and selective approaches. Secondary [46] Strategies to diagnose and treat existent diseases in early stages before significant morbidity occur. Relapse prevention; attenuation of episode duration and severity of episode; early intervention. Tertiary [46] Strategies to reduce negative impact of existent disease by restoring function and reducing disease-related complications. Prevention of cognitive decline; prevention of psychotropic drug use and therefore reduced side effects; prevention of catatonia; prevention of adverse effects of illness on social and occupational functioning.