senior woman lifting hand weights for exercise for depression
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In 2023, it’s common knowledge that regular physical activity can improve physical health and improve mood, but many people still wonder whether physical activity can improve the symptoms of clinical depression.

The answer is a simple “yes.”

Decades of data indicate the relationship between physical activity and depression is clear: it can help reduce depressive symptoms in people diagnosed with clinical depression. However, what’s unclear is exactly how much exercise and physical activity reduces depressive symptoms.

The study “Physical Activity Dose and Depression in a Cohort of Older Adults in The Irish Longitudinal Study on Ageing” addresses this gap in knowledge by posing this research question:

What is the minimal dose of moderate to vigorous physical activity (MVPA) associated with a reduced risk of depression and depressive symptoms in older adults (aged ≥50 years) with and without chronic disease?

This study piqued our interest because we recently published an article on the impact of an organized lifestyle modification protocol on older patients with severe mental illness (SMI) who were either overweight or obese. That study showed an organized intervention can work to reduce weight and BMI in patients with SMI.

To learn about that protocol and read the results, please navigate to the blog section of our website and read our article:

Lifestyle Interventions for People With Severe Mental Illness

Whereas that study used weight loss and BMI as primary metrics, the study on physical activity and depression on older adults in Ireland examined the records of over 4000 patients for signs of reduced depressive symptoms. Researchers analyzed data collected at five time points – roughly every two years – between 2009 and 2018, and compared the relative impact of various amounts of activity on depressive symptoms.

The goal was to find out if the recommended levels of activity and exercise for the general public were sufficient to reduce symptoms in people with depression. Before we dive into the details of this study, let’s review what we know about the health benefits of exercise, and remind ourselves about the detail of current best-practice guidelines for healthy physical activity.

The Benefits of Physical Activity: Overall Health and Mental Health

In 2008, the Centers for Disease Control (CDC) released a set of guidelines for exercise and activity for children, adults, and senior citizens in the United States.  The need for a national set of guidelines for exercise and activity became apparent after the publication of the 1996 Surgeon General’s Report on Physical Activity and Health, which identified a population-level problem with obesity and indicated that on average, U.S. citizens were too sedentary – and becoming more sedentary with each passing year.

The report broadcast a simple message to all U.S. citizens: we need to be more active, because consistent moderate to vigorous activity leads to the following general health benefits:

  • Reduced overall likelihood of disease
  • Reduced risk of serious, chronic illness:
    • Heart disease
    • Type II diabetes
    • Hypertension
    • Colon cancer
  • Improved anxiety symptoms
  • Improved depressive symptoms
  • Increased bone, muscle, and joint health
  • Improved weight management
  • Independence in older adults
  • Reduced falls and fractures in older adults

These guidelines set the standard for physical activity by identifying the minimum amount of time necessary to experience the benefits listed above. In 2019, the CDC released a new set of guidelines, with slight revisions and additions to the original edition. This revised report, called Physical Activity Guidelines for Americans, 2nd Edition, reiterates those basic benefits we list above, and offers the latest information on additional benefits of regular exercise.

CDC 2019: New Data on Importance of Exercise

New research identified the following benefits of exercise for the following demographic groups:

  1. Children age 3 through 5: improved bone health
  2. Youth age 6 to 13: improved cognitive function
  3. Cancer: reduced risk at several know cancer sites
  4. Overall brain health: improved cognitive function
  5. Sleep: improved quality/duration of sleep
  6. Wellbeing: overall improved quality of life.
  7. During pregnancy: decreased weight gain, decreased gestational diabetes, decreased postpartum depression.
  8. For people with chronic illness: decreased likelihood of disease-specific and/or all-cause mortality, improved mobility/function, improved quality of life

Now let’s take a look at what the CDC recommends, so we can compare their recommendations with what the researchers found in the study on physical activity and depression we introduce above.

Physical Activity: What the CDC Guidelines Say

One thing the CDC stresses in the 2019 publication is that any activity is better than no activity. Generally speaking, adults should sit less and move more. To gain the benefits of exercise, they should meet these minimum requirements:

  • Do 150 to 300 minutes of moderate-intensity aerobic activity per week, such as walking, swimming, or jogging
  • Do 75 to 150 minutes of vigorous-intensity aerobic physical activity per week, which can include walking swimming, and jogging, but should also include higher intensity exercise that includes resistance training
  • A combination of moderate and vigorous activity that meets the recommendations above

The CDC added advice for older adults:

  • Older adults benefit from balance training, aerobic training, and muscle-strengthening activities.
  • It’s important to perform activities that do not exceed basic fitness levels
  • Chronic conditions may impact the among and intensity of exercise considered beneficial: each individual should consult a physician for individualized adaptations
  • Older adults who cannot meet the minimum recommendations will benefit from doing as much as they can

Finally, the CDC made these recommendations for all people at any age or any level of fitness:

  • Spread aerobic activity throughout the week for best results
  • Exceeding recommended levels of exercise can increase the benefits of exercise
  • For best results, all people at all age and fitness levels should include muscle-strengthening activities at least twice a week

That information gives us everything we need to compare our daily recommendations with the exercise categories researchers defined in the study on physical activity and depression on older adults in Ireland. Let’s look at that study now.

Physical Activity and Depression Among Older Adults: The Study

Researchers examined records of over 4,000 patients with depression over a 10-year period in order to determine the minimum amount of weekly physical activity required to reduce symptoms of depression.

The research team directed patients to record and report the following information on a weekly basis:

  • Number of days of vigorous, moderate, and walking activities
  • Duration of vigorous, moderate, and walking activities

Researchers used this data to estimate the metabolic equivalent of task (MET) minutes each patient performed each week, then categorized the results into several moderate-to-vigorous physical activity (MVPA) doses. Each dose category was defined as a specific MET per week minimum.

Don’t worry: you don’t have to understand what MET means, because we translated the dose categories to correspond to the levels of activity recommended by the CDC.

First, the research team created three MVPA dose categories.

Traditional 3-dose categories:

  1. Low Dose (<600 MET-min/wk): Below the CDC guidance on minimum METs required per week to experience the health benefits of regular exercise
  2. Moderate Dose (600 to <1200 MET-min/wk): Aligns with CDC guidance on METs required per week to experience the health benefits of regular exercise
  3. High Dose (≥1200 MET-min/wk): Exceeds CDC guidance on METs required per week to experience the health benefits of regular exercise

For further clarity and specificity, the research team created an expanded set with 5 MVPA dose categories.

Expanded 5-dose categories:

  1. No activity. 0 MET/wk: Below CDC guidelines
  2. Low activity. 1 to 600 MET/wk: Below CDC guidelines
  3. Moderate activity. 600 to 1200 MET/wk: Meets CDC guidelines
  4. High activity. 1200 to 2400 MET/wk: Exceeds CDC guidelines
  5. Very high activity. ≥2400 MET/wk: Far exceeds CDC guidelines

Finally, the research team determined the minimally sufficient continuous physical activity dose needed to reduce depressive symptoms in patients with clinical depression.

Physical Activity and Depression Among Older Adults: The Results

Here’s the first – and perhaps most important – result the researchers reported:

“A dose-response association was observed between MVPA dose categories and depressive symptoms.”

That means depressive symptoms varied by the amount of exercise/activity patients performed. When analyzed with the 3-dose category metric, researchers observed the following:

  • A 20% decrease in depressive symptoms for patients with high physical activity compared to patients with low physical activity

In other words, the more the activity, the greater the decrease in symptoms.

When the research team analyzed the data with the 5-dose category metric, they observed the following:

“…an incremental decrease in depressive symptoms for each increasing level of physical activity.”

Again, the more the activity, the greater the decrease in symptoms. Here are the details:

  • Patients meeting recommendations/engaging in a moderate level of activity:
    • 7% reduction in depressive symptoms, compared to no activity
  • Patients exceeding recommendations/engaging in high level of activity:
    • 16% reduction in depressive symptoms, compared to no activity
  • Patients far exceeding recommendations/engaging in very levels of activity:
    • 23% reduction in depressive symptoms, compared to no activity

Now we’ve got a surprising result to share. Remember, the initial research question involved finding the minimum amount of MVPA required for patients to experience a statistically significant reduction in depressive symptoms. Here’s the surprise, in the words of the research team:

“Patients performing 400 to less than 600 MET-min/wk had a 16% lower rate of depressive symptoms compared with participants performing 0 MET-min/wk.”

Why is that a surprise?

Because those MET levels are less than half of the MET levels that correspond with the CDC guidelines for the minimum MVPA per week required to experience the health benefits of exercise.

What This Means for Patients With Depression

In a nutshell, this study indicates that for older adults with a clinically diagnosed depressive disorder, less physical activity than recommended by the CDC can lead to significant reduction of depressive symptoms. Therefore, we can say that for mental health benefits, even a small amount of MVPA per week can work: this data indicates around 100 minutes of MVPA – which can include walking – per week can reduce depressive symptoms, as compared to the 150-300 minutes of MVPA recommended to experience the general health benefits of regular exercise.

Disclaimer: that’s the bare minimum required for a statistically significant effect.

That’s important for people with low default levels of MVPA to understand. It also aligns with the CDC adage any exercise is better than none. We now have a minimum number to attach to the world any: just over an hour and a half a week, or around 100 minutes. For people with depression with a sedentary lifestyle, that may seem well within reach, while 150-300 minutes of MVPA plus 75-150 minutes of vigorous-to-intense activity may seem far beyond reach.

In addition, the study confirms that while less exercise than recommended by the CDC can improve mental health, more exercise than recommended by the CDC leads to incrementally greater reductions in depressive symptoms.

That’s information we can share with out patients right away, and convince them that no matter their current level of activity, simply taking a 20-minute walk five days a week – based on the data in this study – can reduce depressive symptoms by up to 16 percent, compared to not walking or engaging in any physical activity at all.