“Going for a brisk stroll could play an important role in fighting depression,” BBC News has reported.

Current evidence suggests that physical activity can be useful for reducing the symptoms of depression, but previous examinations of research have not specifically looked at the benefits of walking for depression. In order to improve our understanding of the issue, Scottish researchers conducted a systematic search for all relevant medical trials on the subject, combining their results into a single analysis.

The researchers found eight relevant studies featuring a total of 341 people. Overall, the combined results of these trials suggested that walking reduced the symptoms of depression. However, the trials were small, and they varied in the types of people they included, the walking programmes they used and what they compared walking to. This limits the strength of the conclusions that can be drawn about the effects of walking in specific groups of people with depression.

However, this is not the first research to have suggested that physical activity is beneficial for depressive symptoms. The National Institute for Health and Clinical Excellence (NICE) currently recommends considering structured group physical activity programmes as a treatment option for some forms of depression.

As the authors of the review note, walking is a form of physical activity that most people can take part in safely and at minimal cost. More research is now needed to determine exactly what duration and frequency of walking is most effective for depressive symptoms.

Where did the story come from?

The study was carried out by researchers from the Universities of Stirling and Edinburgh. Sources of funding were not reported. The study was published in the peer-reviewed journal Mental Health and Physical Activity.

The study was reported appropriately by the BBC.

What kind of research was this?

Physical activity has been found to reduce depressive symptoms, but the researchers behind this study say that it is not known whether walking specifically has the same effect. They say, however, that walking can be easily undertaken by most people, fits into our daily schedules, is low-cost and comes with little risk of adverse effects. The researchers set out to conduct a systematic review of the evidence on the effects of walking on depression. They also set out to perform a meta-analysis, which is a pooling of the results of the individual studies.

A systematic review is the best way to summarise all of the existing research on the question of interest, as, during a systematic review, researchers should rigorously search for and analyse all relevant high-quality studies available on a subject. Systematic reviews include relevant studies regardless of their results, rather than just focusing on those that support or contradict a particular theory. The results of the studies in a systematic review may be statistically pooled if the studies are similar enough in method to produce meaningful results. Pooling very different types of studies (for example those with very different study populations) will produce results that don’t improve the researchers’ understanding of the effect of an intervention.

What did the research involve?

The researchers searched 11 literature databases to identify randomised controlled trials of walking as a treatment for depression. They then statistically pooled the results of eligible studies to assess whether walking reduced depressive symptoms compared with a control treatment that did not involve walking.

The researchers included any studies in adults with any form of depression, excluding those in which depression was being examined as part of bipolar disorder or where all the participants were recruited because they had a specific medical condition, such as cancer. Studies of any kind of structured or semi-structured walking programmes were included. Studies where other types of exercise were also part of the activity programme were excluded. Stretching to warm up or cool down before walking was permitted. The comparison group in eligible trials could be those receiving no treatment, usual depression care or a treatment that was also given to the walking group (for example, cognitive behavioural therapy). Depressive symptoms could be assessed using any symptom scale.

Information on the study characteristics and results was extracted from eligible studies, and the quality of the trials was assessed. Results were pooled using standard methods. The researchers looked at the effect of walking overall, and also at indoor and outdoor walking and group walking specifically.

What were the basic results?

The researchers identified seven trials that fully matched their inclusion criteria. They also included an additional trial that included people who either had moderate depression or who had a high body mass index (BMI). They did this as the trial was relatively large, and included a considerable number of people with depression. The trials were generally quite small, with between 11 and 127 people in each trial. The trials included 341 people in total. They varied in their quality, with only one trial reporting on, and meeting, all four of the quality indicators used by the reviewers.

There was a lot of variability between these trials, including differences in the types of people that were recruited, the settings in which they were treated, how severe their depression was and how it was diagnosed. The trials also varied in the types of walking programmes they used: whether they were supervised; indoor (for example, on a treadmill) or outdoor; whether they were group walks; and the duration and frequency of the walks performed. The walks ranged from 20 to 50 minutes, and the programmes lasted up to six months. The control groups were assigned therapies including usual care, stretching and relaxation exercises, social contact or other kinds of support (talking to a researcher or a support group).

Pooling the results of these studies showed that, overall, walking did significantly reduce depressive symptoms. There was a high level of variability across the results of the studies, however, with one finding a better outcome with the control treatment, one finding no significant benefit of walking, and the other studies finding varying levels of benefit. The researchers then conducted a further two separate analyses – one including only the four best trials and one excluding the study that had recruited people with high BMIs. Both of these still found that walking significantly reduced depressive symptoms.

The researchers also found that walking had a significant effect in trials of indoor walking, outdoor walking and group walking if these were looked at separately. The researchers noted that the variability in the designs of these studies meant that the pooled results may not be directly applicable to specific groups of people.

How did the researchers interpret the results?

The researchers concluded that walking significantly reduced the symptoms of depression in some populations. However, they say that there are limitations to the existing studies and suggest that further research is needed to determine exactly what type of walking programmes (frequency, intensity, duration) would be best for people with depression being treated in primary care, such as by a GP.

Conclusion

Physical activity is already thought to have a beneficial effect on depressive symptoms, and the UK’s National Institute for Health and Clinical Excellence (NICE) currently recommends considering a structured group physical activity programme as a treatment option for people with mild-to-moderate depression and persistent ‘subthreshold’ depressive symptoms:

subthreshold depression is defined as a person meeting fewer than five symptoms on an accepted set of diagnostic criteria for identifying depression

mild depression is defined as having five of the symptoms (or a few more) required to make a diagnosis, but only minor functional impairment

moderate depression is when symptoms or functional impairment are between mild and severe

NICE recommends that structured group physical activity is delivered in groups that are supported by a competent practitioner, and that it should typically consist of three sessions per week (lasting 45 minutes to 1 hour) over 10–14 weeks.

This new study suggests that walking is an activity that can help to reduce the symptoms of depression. It is a systematic review, the form of study considered to be the best way to determine what all the relevant research available says about a particular question. However, there are some limitations to this review, because the available studies are small and vary in their methods and results. This means that it is difficult to be certain exactly what level of benefit certain types of people with depression will get from walking. As the authors of the review state, more research is needed to determine which type of walking programme is best for people with depression being treated in primary care.

Analysis by Bazian

Edited by NHS Website