Walking for depression or depressive symptoms: A systematic review and meta-analysis

Abstract

Problem

Depression is a common disorder worldwide. Most patients are treated within primary care and antidepressant treatment is not recommended for people with mild depression. Physical activity has been shown to alleviate depression but it is not known whether the less vigorous activity of walking – a potentially widely acceptable and safe intervention – confers such benefit.

Method

Eleven databases were systematically searched for randomised, controlled trials of walking as a treatment intervention for depression, from database inception until January 2012. Meta-analyses were carried out on all trials eligible for inclusion and on sub-groups of outdoor, indoor and group walking.

Results

Of the 14,672 articles retrieved, eight trials met the inclusion criteria. The pooled standardised mean difference (effect size) was −0.86 [−1.12, −0.61] showing that walking has a statistically significant, large effect on symptoms of depression. However, there was considerable heterogeneity amongst the interventions and research populations and it is uncertain whether the results can be generalised to specific populations such as primary care patients.

Conclusions

Walking has a statistically significant, large effect on the symptoms of depression in some populations, but the current evidence base from randomised, controlled trials is limited. Thus, while walking is a promising treatment for depression or depressive symptoms with few, if any, contraindications, further investigations to establish the frequency, intensity, duration and type(s) of effective walking interventions particularly in primary care populations would be beneficial for providing further recommendations to clinical practitioners.

Introduction

Depression is an illness or mood disorder with a variety of symptoms, the most defining being an inexplicable, enduring feeling of sadness (loss of positive affect). It is categorised as mild, moderate or severe depending upon the number and severity of the symptoms (WHO, 2010). It is a common mental health problem, estimated in 2000 to be the fourth leading cause of disease burden worldwide (Ustun et al., 2004, WHO, 2003). It causes a level of morbidity comparable to or worse than other common chronic diseases such as asthma and diabetes (Moussavi et al., 2007). In the UK over 75% of patients with depression are treated solely within primary care (NICE, 2010) where prevalence is estimated at 7% (Ostler et al., 2001).

Depression is commonly treated with antidepressant medications, psychological therapies or a combination of both. The efficacy of antidepressants for mild depression has been questioned (Moncrieff & Kirsch, 2005) and they are not recommended to be used routinely by people with persistent sub-threshold depressive symptoms or mild depression in the first instance (NICE, 2010). There is also a range of side effects (Demyttenaere, 2003), many people do not like taking medicines (Givens et al., 2006, Kessing et al., 2005, Maxwell, 2005, Townsend et al., 2003) and early drop-out rates in clinical trials vary from 12% to 40% (Cipriani et al., 2009, Kirsch et al., 2008). Psychological therapies are resource intensive, and may require cognitive capabilities a person with depression cannot attain. Consequently, for many years there has been interest in physical activity (and other alternative therapies) as a stand-alone or adjunctive treatment for depression (Scottish Intercollegiate Guidelines Network, 2010). Several systematic reviews (Lawlor and Hopker, 2001, Mead et al., 2008, Mead et al., 2009, Sjosten and Kivela, 2006) and a review of reviews (Daley, 2008) have concluded that exercise appeared to improve symptoms of depression, but that the methodological quality of available trials was often too poor to reach a robust conclusion. A further meta-analysis by Stathopoulou (Stathopoulou, Powers, Berry, Smits, & Otto, 2006, p. 188) concluded that “exercise can be a powerful intervention for clinical depression”, and another systematic review of the effect of exercise in clinically depressed adults by Krogh et al. found that there was a short-term positive effect of exercise on depression but no positive long-term effect (Krogh, Nordentoft, Sterne, & Lawlor, 2011). For patients with persistent sub-threshold or mild to moderate depression, current UK NICE guidelines (NICE, 2010) recommend structured physical activity programmes, individual guided self-help based on cognitive behaviour therapy (CBT) principles and/or computerised CBT as treatment choices. It is recommended that the physical activity programmes are group based and led by a trained practitioner thrice weekly for 45 min to 1 h for a period of 10–14 weeks.

Walking is a form of physical activity that has the potential to alleviate depression. When taken outdoors, the addition of being able to observe or experience an attractive natural environment has been shown to have a restorative effect, decreasing levels of stress, (Hartig et al., 1991, Kaplan and Kaplan, 1989, Ulrich, 1983) which could contribute to reducing symptoms of depression. Walking has the advantages of being easily undertaken by most people, incurring little or no financial cost, having minimal risk of adverse effects and being relatively easy to incorporate into daily living. Consequently, walking is promoted in many developed countries throughout the world (Steps Project, 2011, Centers for Disease Control and Prevention, 2011, Health Canada, 2011, International Longevity Center-USA, 2011, Natural England, 2011, NHS Choices Information, 2011, Paths for All, 2011, Welsh Assembly Government, 2011) to counteract increasingly sedentary lifestyles and the health consequences of physical inactivity. While existing systematic literature reviews with meta-analyses (Krogh et al., 2011, Lawlor and Hopker, 2001, Mead et al., 2009) have found positive, but not conclusive evidence, to support exercise as an intervention for depression, to our knowledge no review to date has evaluated the effectiveness of specific types of physical activity.

A variety of mechanisms to explain why physical activity might reduce depressive symptoms has been suggested (Craft & Perna, 2004). These include biochemical (including endorphin and monoamine hypotheses), physiological (thermogenic, cardiovascular fitness, and sleep improvement hypotheses) and psychological and psychosocial hypotheses such as distraction, self-efficacy and enhancement of self-esteem (Sonstroem & Morgan, 1989) or increasing positive affect (Clark and Watson, 1991, White et al., 2009). Whichever mechanism or combination of mechanisms are responsible for physical activity reducing depressive symptoms, there is uncertainty regarding the optimum dose (duration and frequency of sessions, length of programme) and intensity and which specific type(s) of physical activity benefit depression (Mead et al., 2008). It is not known whether walking is a form of physical activity that is sufficiently vigorous to stimulate sufficient biochemical or physiological changes to be an effective treatment for depression and whether walking interventions contribute to or diminish the overall effect sizes reported.

If the available evidence were able to demonstrate that walking is an effective physical activity for the treatment of depression, this knowledge could inform current recommendations and give health professionals greater confidence in the benefits of walking when advising patients who are depressed. We therefore carried out a systematic review of the existing literature to examine the effectiveness of walking as an intervention for alleviating depression in adults, and performed a meta-analysis on relevant data. Further, we considered walking outdoors, walking indoors and walking in a group.