Even a little exercise could help reduce risk

There is increasing evidence that lifestyle changes can reduce depressive symptoms. A 2014 analysis of 21 studies found that a diet high in fruit, vegetables, fish, and whole grains may be associated with a reduced depression risk. And a 2022 review of studies found that exercise alleviated depressive symptoms.

However, few studies have looked at how much exercise is needed to have a positive impact on depression.

Now, a 10-year study has found that even small amounts of exercise can reduce depression among older adults — people aged 50 years and older.

The study, which was funded by the Health Research Board (HRB) Ireland, and appears in JAMA Network Open, found that a 20-minute brisk walk, 5 times a week significantly reduced the risk of depression.

Study author Dr. Eamon Laird, a postdoctoral research fellow at the University of Limerick, Ireland, told Medical News Today why the team carried out the study:

“Depression is unfortunately increasingly prevalent in the older adult population and is associated with increased risk of chronic conditions including cardiovascular disease (CVD), cognitive decline, mortality, and suicide. […] Physical activity has been previously shown to be associated with reduced risk of depression; however, no one has yet investigated what is the bare minimal dose of physical activity that might provide benefits.”

The researchers included 4,016 participants from The Irish Longitudinal Study on Ageing (TILDA), a large-scale, longitudinal study that aims to improve the aging experience of people in Ireland. They collected data at five time points between October 2009 to December 2018.

At each time point, the researchers collected detailed information on demographic, health, lifestyle, and social factors through either a self-completed questionnaire, nurse health assessment, or interview.

They assessed depressive symptoms using the short form of the Center for Epidemiological Studies Depression (CES-D). From this, they classified major depression as either a CES-D score greater than or equal to nine and/ or a major depressive episode at any of the data collection time points.

At each data point, participants self-reported their physical activity for the previous 7 days. They had to record on how many days and for how long they undertook vigorous, moderate, and walking activities.

The researchers then estimated the total number of metabolic equivalent of task (MET) minutes per week for each individual, and categorized them into low, moderate, or high physical activity.

“We found that older adults performing as little as 20 minutes a day (for 5 days a week) of moderate to vigorous physical activity (MVPA) had a 16% lower risk of depressive symptoms and a 43% lower odds of depression [than those undertaking no exercise],” Dr. Laird told us.

In the three exercise categories, the researchers saw an increase in benefit as their exercise level increased. Individuals taking the most exercise were 20% less likely to experience depression than those in the low exercise category.

Even people taking only a minimal amount of exercise were 16% less likely to experience depression than those who took no exercise.

“Twenty minutes was the minimal dose but we also observed that the greater the level of activity the greater the mental health benefits.”

– Dr. Eamon Laird

Exercise also lowered the risk of both depressive symptoms and major depression for participants with chronic disease, and similarly, the effect increased with greater activity levels, as Dr. Laird explained.

“Specifically for those with chronic diseases, for depressive symptoms, participants showed significantly reduced risk (8%) at the WHO guidelines threshold of 30 mins a day [per] 5 days [a] week, though the greatest reductions occurred with increasing activity dose,” the researcher told MNT.

“In essence, those with chronic disease may find greater benefits and it could be a number of mechanisms — anti-inflammatory, immune function, heart-brain cross-talk, improved muscle function etc,” he added.

Dr. Thomas MacLaren, consultant psychiatrist at Re:Cognition Health, who was not involved in the study, welcomed the findings.

“Chronic health issues are known to make depression worse and are even a risk factor for developing depression. The study finding of a dose-dependent relationship for this group provides a hugely encouraging sign that it is worth taking regular exercise, and even increasing your daily routines, like brisk walking, to further improve your mood,” he told us.

There are several reasons why exercise might reduce the risk of developing depression, or alleviate depressive symptoms.

Exercise increases blood flow to the brain and the hypothalamic-pituitary-adrenal (HPA) axis, which influences motivation and mood, and decreases reactivity to stress. It also increases the level of endorphins, the body’s natural pain and stress relievers.

And the effects are not only physical, as Dr. MacLaren explained:

“Exercise helps the body release endorphins and improves fitness levels. These positive effects can naturally improve your mood. It can also have an indirect effect on regulating your daily routine and providing more social contact, which is really important in fighting depression.”

Dr. Laird agreed, emphasizing that exercise should form part of a healthy lifestyle for the greatest benefit.

“Try and build it [exercise] into a routine with hobbies or activities that are enjoyed and we would recommend it with others as social interactions, particularly with activity, can also have extra mental health benefits,” he said.

“Remember that it is one component and that nutrition and a healthy lifestyle will also give additive benefits in addition to the physical activity,” Dr. Laird added.