While we know of the physical and psychological benefits for people in general, we have less insight regarding the effects of exercise on those with depression.

Iowa State University (USA) researchers set out to see if exercise improved depression symptoms in the short term. Today, we look at the prevalence of depression in the general population before turning to the positive results from the new studies.

Depression prevalence

Syndromes of depression are pretty prevalent among adults worldwide. An examination of 21 countries discovered a 12-month prevalence of unipolar depression to be five percent.

The lifetime prevalence of depression is about 12 percent, according to surveys from 14 countries. There appears to be a striking difference in the incidence of depression when we stratify it by income:

• In developed countries (for example, the United States and Europe), the lifetime prevalence of depression is about 18 percent.
• In developing countries (for example, China, Mexico, and Brazil), the lifetime prevalence of depression is nine percent.

The significant differences in depression risk may be secondary to sampling errors, challenges with applying diagnostic criteria in all locations, or genetic and cultural factors.

Depression risk factors

Several factors are associated with an individual having a higher chance of suffering from depression. Here are some of them:

• Age. Major depression, at least in the United States, is more common among younger adults than older individuals. One community survey of adults 55 years and older showed that the one-year prevalence of major depression decreased with increasing age. However, depression appears more frequently among those with more medical challenges and assisted living or skilled nursing facilities residents.
• Income. There appears to be a slightly higher probability of suffering from depression among those with a lower household income than those making US $70,000 or more.
• Marital status. The lifetime prevalence of depression among those who are married (or cohabitating) is around 8 percent in the USA, compared with 13 to 14 percent for the never married, divorced, separated, or widowed.
• Race/ethnicity — In the United States, the highest prevalence of major depression is among Native Americans, with the lowest rates in Asians/Pacific Islanders. The lifetime prevalences of depression are 12 percent for Asians, 15 percent for Blacks, 16 percent for Hispanics, 28 percent for Native Americans, and 23 percent for whites.
• Sex — In the USA and elsewhere, the prevalence of depressive syndromes is about twice as high among females as males.

Depression and exercise

For the study, researchers recruited 30 adults experiencing major depressive episodes.

The subjects completed electronic surveys about depression symptoms before, in the middle, and after 30 minutes of moderate-intensity cycling. The participants also completed surveys afterward at the 25-, 50-, and 75-minute marks.

The subjects returned a week later. Those who had cycled during the first lab visit repeated the activity, but only after sitting for 30 minutes first. The other group reversed the exercise and rest order.

Depression symptoms better for up to 75 minutes

The surveys examined changes in three main features of depression, including depressed mood state, challenges experiencing pleasure from activities previously enjoyed (anhedonia), and decreased cognitive function.

Here are the findings:

During the cycling experiment, participants’ depressed mood state improved over the 30 minutes of exercise and up to 75 minutes afterward.

In terms of the ability to feel pleasure, the benefits of exercise began to wear off after about 75 minutes. Still, the exercise group scored better on this measure than the non-exercisers.

A single session can improve a depressed mood for at least 75 minutes, with drops in anhedonia (not experiencing pleasure) not lasting as long.

Cognitive behavior therapy

After the eight-week program, both groups showed improvement. Those who did an exercise program before cognitive behavior therapy had the most impressive drop in depressive symptoms.

Participants who exercised also reported a quicker, more robust connection with their therapists. The study authors suggest that exercise may prime the brain to engage in more emotionally challenging work with a therapist.

Thank you for joining me. If you have symptoms of depression, please let your health care provider know right away.