Should we be targeting exercise as a routine mental health intervention?

In both the developed and developing world, the processes of industrialisation and urbanisation over the past century have led to a marked reduction in physical activity. Western lifestyles are predominantly sedentary, with a lack of physical activity recognised as amajor health issue. Physical activity has a range of welldocumented health benefits, ranging from reduction in overall mortality to primary prevention of obesity, diabetes, cardiovascular disease, osteoporosis and some types of cancer (1). While there is validity in applying this as part of a holistic approach to enhance general health and manage physical comorbidities, insufficient attention has been given to the role of physical activity as an intervention specifically targeted at mental health issues. Research into physical activity in a psychiatric context has mainly focussed on treatment of anxiety and depression (1,3). There are methodological problems that limit their generalisability including the fact that there are few randomised controlled trials that have different study cohorts and methodologies (2). There is still a strong signal from these trials that exercise, irrespective of type, is associated with a reduction in depressive and anxiety symptoms in the short term (2). In a highquality randomised controlled trial, 80 participants with mild to moderate major depressive disorder were randomised to four different dose-aerobic exercise groups and an exercise placebo control group in a 12-week study. The higher energy expenditure group showed significantly greater reduction in Hamilton Rating Scale for Depression scores (47% from baseline) than the lower energy expenditure group (30%) and control (29%) (4). In a randomised controlled trial (n 1⁄4 156), comparing sertraline, exercise and the combination of sertraline and exercise for the treatment of major depression, the exercise group showed a significantly lower relapse rate than the sertraline and the sertraline plus exercise group after 6 months. Remission rates at the end of 16 weeks did not differ significantly (5). In addition to an effect in treating depression, there is evidence of regular exercise being protective against the development of depression in both crosssectional and prospective community studies (6). Conversely, a sedentary lifestyle is a known risk factor for the development of depressive symptoms (7). A systematic review examined the effects of exercise interventions in reducing or preventing both anxiety and depression in children and adolescents in the general population. A small positive effect in favour of exercise was reported (8). Regular exercise may have a role as both an important preventative and treatment strategy for depression. The mechanism of action of physical activity onmental health is not definitively established. It is thought to involve one or more of endorphin release, facilitation of monoaminergic neurotransmission, distraction from negative cognitions and stimuli, promotion of a sense of selfefficacy and enhancement of social interaction in group activities (9). Physical activity may enhance neurotrophic factors and hence augment brain plasticity. This may enhance executive cognitive functions and modulate the effects of stress on neural circuits (10). Physical activity as part of a broader lifestyle intervention may operate by enhancing behaviours such as organisation, proactivity and taking ownership of one’s life and health, increasing ones sense of control and engagement in life, thereby improving mood. Taken together, this data suggest that clinicians could profitably utilise interventions aimed at increasing physical activity both in the acute treatment and in ongoing lifestyle management of individuals with mood and anxiety disorders. This may have additional prophylactic benefits in addition to the well-established broader health benefits that are widely accepted.