Depression: Even a little exercise can help reduce risk

There is growing evidence that lifestyle changes can reduce depressive symptoms. A 2014 analysis of 21 studies found that a diet high in fruits, vegetables, fish, and whole grains may be associated with a reduced risk of depression. And a 2022 review of studies found that exercise relieved 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 in older adults — people age 50 and older.

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

Study author Dr. Eamon Laird, a postdoctoral researcher at the University of Limerick, Ireland, explained Medical News Today why the team conducted the study:

“Unfortunately, depression is becoming more prevalent in the older adult population and is associated with an increased risk of chronic conditions, including cardiovascular disease (CVD), cognitive decline, mortality and suicide. […] Physical activity has previously been associated with a reduced risk of depression; however, no one has yet researched the absolute minimum dose of physical activity that could produce benefits.

The researchers included 4,016 participants from The Irish Longitudinal Study on Aging (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 and December 2018.

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

They assessed depressive symptoms using the Center for Epidemiological Studies of Depression (CES-D) short form. 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, the participants self-reported their physical activity over the past 7 days. They had to keep track of how many days and for how long they did strenuous, moderate and walking activities.

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

“We found that older adults who performed just 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 risk of depression. [than those undertaking no exercise]’ said Dr. Laird us.

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

Even people who exercised only minimally were 16% less likely to develop depression than those who did not exercise.

“Twenty minutes was the minimum dose, but we also saw that the greater the activity level, 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 illness, and similarly, the effect increased with higher activity levels, as Dr. Laird explained.

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

“Essentially, people with chronic disease may find greater benefits and it could be a number of mechanisms — anti-inflammatory, immune function, heart-brain crosstalk, 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 problems are known to exacerbate depression and are even a risk factor for developing depression. The research finding of a dose-dependent relationship for this group is a hugely encouraging sign that it’s worth getting regular exercise and even increasing your daily routines, such as brisk walking, to further improve your mood,” he told us.

There are several reasons why exercise can reduce the risk of developing depression or relieve depressive symptoms.

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

And the effects aren’t just physical, as Dr. MacLaren explained:

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

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

“Try to build it up [exercise] into a routine with hobbies or activities that are fun and we would recommend to others because social interactions, especially with activities, can also have additional mental health benefits,” he said.

“Remember, it’s one component and nutrition and a healthy lifestyle will provide additional benefits in addition to physical activity,” added Dr. Grant it.