Currently, depression and anxiety are the most common mental health problems (Carek, Laibstain, & Carek, 2011) with between 12%-32% of people in developed countries suffering symptoms (Haller, Cramer, Lauche, Gass, & Dobos, 2014). Women are nearly twice as likely as men to develop depressive and anxious disorders in their lifetime. There are many treatments available including pharmacological agents and psychotherapy and behavioural based therapies, each having varying success from one individual to the next. Often patients do not respond to the first anti-depressant prescribed and 15-33% will not respond to multiple interventions meaning that long-term treatment is often required (Carek et al., 2011). These factors along with the unwanted side effects and stigma that can often accompany pharmacological agents has lead to a need for alternative, complementary forms of treatment to be investigated (Josefsson, Lindwall, & Archer, 2014).
The effects of physical activity on depression and anxiety are well established with effects estimated as medium and large in clinical populations and around half as great in nonclinical cases (Josefsson et al., 2014; Rebar, Stanton, Geard, Short, Duncan, & Vandelanotte, 2015). In a randomised, controlled study comparing low and high frequency exercise with high frequency exercise plus group based intervention in clinical populations the results were significant. Both groups which were exercising three or more times per week (high frequency exercise and high frequency plus group based intervention) reported lower depression scores on the Beck Depression Inventory (BDI-II) at 4 weeks (13.2 +/- 7.3 and 11.7 +/- 3.1) and 8 weeks (10.9 +/- 8.1 and 9.6+/- 2.5) versus the low frequency (one time per week) group (22.4 +/- 7.5 and 20.7 +/- 6.3). As shown in these results, although there was substantial short and longer term benefit from high frequency exercise, there was little additional benefit when group based intervention was added. It has been proposed that the lack of additional effect seen when the group intervention was added may be in part due to the relatively short time frame of the study (8 weeks) not allowing the group sufficient time to create significant bonds (Legrand & Heuze, 2007). However, the almost halving of BDI-II scores clearly shows the benefits of high frequency exercise in clinically depressed subjects.
With much of the research focused on the effects of physical activity, exercise and sport in clinically depressed subjects, little attention has been given to the potential benefits to nonclinical populations (Rebar et al., 2015). In a Meta-Meta-Analysis of the effects of physical activity on depression and anxiety, Rebar et al. (2015) aimed to quantify the effects of physical activity on depression and anxiety in non-clinical populations. In their analysis of 92 studies involving 4,310 participants (depression) and 306 studies with 10,755 participants (anxiety) they found that physical activity reduced depression by a medium effect (SMD = -0.50; 95% CI: -0.93 to -0.06) and anxiety by a small, but significant effect (SMD = -0.38; 95% CI: – 0.66 to -0.11). This data provides strong evidence that physical activity reduces depression and anxiety in non-clinical populations as well as clinical populations. Currently only around 12% of depressed of people seek treatment for their condition and only 18-25% of those who do seek treatment receive adequate treatment (Josefsson et al., 2014). The evidence that both clinically and non-clinically depressed populations can benefit from a low cost alternative to traditional treatment which also provides other health benefits makes physical activity, exercise and sport at the very least a positive adjunct to pharmacological and psychological treatments.
Adolescence is often a difficult time for many young people and with a relatively more sedentary lifestyle than previous generations the impact of physical activity (or lack thereof) on adolescent populations is relevant. In their study of 72 classes across 24 urban junior high schools in China, Hong et al. (2009) found that physical activity was negatively associated with depression amongst adolescents. The study also revealed that students who spent as little as one hour per week in physical activities (outside of school physical education) were 37%-47% less likely to be depressed than those who did not (Hong et al., 2009). This study supports previous evidence that physical activity reduces risk for future escalations in depression (Jerstad, Boutelle, Ness, & Stice, 2010) with correlational evidence suggesting those who are regularly physically active have a 45% lower chance of developing clinically depressive symptoms and between 28- 48% less chance of clinical anxiety symptoms. (Physical Activity Guidelines Advisory Committee, 2008, as cited in Rebar et al., 2015). These findings have potential implications for future research and policy decisions. Increased levels of physical activity, exercise and sport may offer a low risk intervention worthy of consideration by schools and governments alike. More research in this area exploring the relationship between varying physical modalities and depression are suggested with a view to prevention and treatment strategies through exercise for adolescents.
Although the positive relationship between physical activity, exercise and sport is widely accepted, there is little agreement on the mechanisms responsible (Crone et al., 2006). The complex aetiology of depressive symptoms posit that no single treatment is effective for all patients (Bakhtiari et al., 2014). Therefore, it is likely that the anti-depressive and anti-anxiety effects of physical activity, exercise and sport are due to a variety of mechanisms spanning psychological and neurophysiological realms (Carek et al., 2011; Craft, 2005; Craft & Perna,
2004; Rebar et al., 2015). In fact, it has been argued that it may, in fact, be the sheer act of exercising, rather than the effect of exercise that brings about these positive changes (Crone et al., 2006). This is supported by a number of studies which show reductions in depressive symptoms are not dependant on changes in fitness levels and that small incremental increases in physical activity can have significant benefits for mental health (Hong et al., 2009; Rebar et al., 2015). In a 2005 study, Craft (2005) examined the anti-depressive effects of exercise as well as two plausible psychological mechanisms for these effects: self efficacy and distraction. Self efficacy is an individual’s belief that they possess the skills necessary to successfully complete a given task as well as the confidence that the task is capable of being completed with the desired outcome obtained. The ability of exercise to provide a meaningful mastery experience may provide an effective mode to enhance efficacy beliefs. Distraction refers to a response style in which the individual busies oneself in an engaging activity in an attempt to distract themselves from their depressed mood (Craft, 2005). Given the very nature of exercise and its inherent focus requiring qualities, distraction is a plausible theory. Craft (2005) concluded that exercise was associated with a reduction in symptoms of depression. Support was also found for coping self efficacy as a potential mechanism, however there was limited support for distraction as a potential mechanism.
A potential barrier to the use of physical activity, exercise and sport as treatments for symptoms of depression and anxiety is the reciprocal nature of the relationship (Jerstad et al., 2010). Depression and anxiety reduce the likelihood of increased exercise due to the lack of motivation, apprehension and self-consciousness inherent in these disorders. However, these concerns may be mitigated by a focus on the mental rather than physical improvements of exercise (Conn, 2010) as well as the use of supervised and less imposing exercise programs. It has been shown that just 20 minutes of moderate exercise per day, 3 times per week is enough to significantly reduce the symptoms of depression (Craft & Landers, 1998). Therefore, recommendations to increase exercise should centre around ease of access, psychological benefits and enjoyment rather than intensity and physical benefits. See also previous blog re: Motivation.
A review of the available literature provides comprehensive support for the use of physical activity, exercise and sport as first line treatments for mild to moderate depressive and anxious conditions and as an adjunct to pharmacological and psychological interventions for severe cases in clinical and non-clinical populations. Although early studies were plagued by inconsistencies in methodologies, recent studies and reviews of previous studies have shown conclusively that regardless of the methods used, a strong negative correlation between physical activity, exercise and sport and depression and anxiety exists (Conn, 2010; Craft, 2005; Josefsson et al., 2014). Further investigations in to the mechanisms underlying the mental health benefits of physical activity, exercise and sport are recommended to better understand this correlation (Crone et al., 2006). A better understanding of the mechanisms that drive this correlation may provide a better understanding of early warning signs of depressive and anxious symptoms, especially in adolescents. Better understanding of the mechanisms involved may also help to inform physical activity, exercise and sport guidelines and policies in schools.