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.Keywords: depression, physical activity, walking, systematic review, meta-analysis 2
IntroductionDepression 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 (WHO, 2003;Ustun, Ayuso-Mateos, Chatterji, Mathers, & Murray, 2004). 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 anti-depressant medications, psychological therapies or a combination of both. The efficacy of anti-depressants 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 (Ma...