A new study indicates that a drop in physical activity during the COVID-19 pandemic is closely related to a rise in symptoms of depression in young adults, according to results published in the journal Proceedings of the National Academy of Sciences of the United States of America. But the study also shows that getting more physical activity doesn’t seem to help with depression in this population, leaving it unclear whether less physical activity is a cause or a symptom of depression.
Researchers looked at health data from college students at the University of Pittsburgh that covered a range of areas — including physical activity, sleep habits, use of time and mental health — both before and during the COVID-19 pandemic. Overall, there were “dramatic changes” in these areas, demonstrating unhealthy changes to certain habits and lower productivity along with declining mental health among study participants. At the start of the pandemic, the average number of daily steps dropped from about 10,000 to about 4,600, an unprecedented decline in physical activity. Sleep time increased by about 25 to 30 minutes per night. Time spent socializing dropped by over 50% to less than 30 minutes per day, and “screen time” on phones and computers more than doubled to over five hours per day. Perhaps not surprisingly, at the same time, the proportion of participants at risk for clinical depression — based on their reported thought processes and symptoms — increased to a range of 46% to 61% throughout the pandemic, representing an increase of up to 90% at the peak of this risk level.
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Less physical activity linked to depression risk
By looking at how changes to lifestyle factors — including physical activity — were linked to depression risk both before and during the pandemic, the researchers found that these changes were much more closely tied to depression since the onset of the COVID-19 pandemic. Before the pandemic, there was little to no link between a decrease in physical activity and an increase in depression risk. But since the pandemic began, a drop in physical activity was a strong predictor of who would develop signs of depression. In contrast, people who kept up with their pre-pandemic levels of physical activity were far less likely to develop signs of depression.
But an intervention that was carried out as part of the study cast doubt on whether lower physical activity actually contributed directly to the increased risk for depression. In June 2020, half of a subset of 205 study participants were randomly assigned to receive an incentive to take 10,000 steps each day ($5 per day this was achieved) for two weeks. Compared with a control group that received no incentives, the number of steps participants in the active group took (all participants wore a fitness tracking device) increased by an average of about 2,300 per day, with a corresponding increase in physical activity of almost 40 minutes per day. But at the end of the intervention period, participants in the active group showed no overall improvement in mental health compared with the control group. What’s more, participants who stayed more active for the next four weeks — with no incentives to do so — also showed no improvements in mental health symptoms.
The researchers concluded that despite uncertainty about causes and effects, getting less physical activity was strongly linked to the risk for depression. “Physical activity may have important interactions with other lifestyle behaviors such as social interactions, for example because it is often undertaken in a social context,” they wrote, adding that future studies “could attempt to restore physical activity in conjunction with other important lifestyle habits.”
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