This review included trials which showed a positive effect of exercise in people with clinical depression only and excludes postnatal depression, bipolar disorder or depression with co-morbid illness such as diabetes or cancer. Similarly, this review only includes structured exercise interventions and not leisure time physical activity, sports participation, or other forms of exercise such as Yoga, Tai Chi, stretching or other lower intensity exercise. Finally, since no non-aerobic exercise interventions such as resistance training were examined, we cannot compare the loading parameters for each exercise modality.