Assessment of Bidirectional Relationships Between Physical Activity and Depression Among Adults (2019) Choi et al

Andy

Andy

Retired committee member
While many studies have found associations between greater levels of physical activity and lower rates of depression, a key question has remained – does physical activity actually reduce the risk of depression or does depression lead to reduced physical activity? Now a team led by Massachusetts General Hospital (MGH) investigators has used a novel research method to strongly support physical activity as a preventive measure for depression. Their report is being published online in JAMA Psychiatry.

“Using genetic data, we found evidence that higher levels of physical activity may causally reduce risk for depression,” says Karmel Choi, PhD, of the Psychiatric and Neurodevelopmental Genetics Unit in the MGH Center for Genomic Medicine, lead author of the report. “Knowing whether an associated factor actually causes an outcome is important, because we want to invest in preventive strategies that really work.”
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https://neurosciencenews.com/exercise-depression-10619/

I've posted this not for the headline story but two parts of it. One,
GWAS results for physical activity were available for two different measures: one based on 377,000 participants’ self-reports of physical activity and the other based on readings of motion-detecting sensors called accelerometers, worn on the wrists of more than 91,000 participants. The GWAS for depression was based on data from more than 143,000 participants with and without this condition.
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they have data from 91,000 people who wore accelerometers, 91,000 people who didn't find them so annoying that they refused to wear them. Admittedly changes in technology over time may (probably) have made them more comfortable but it shows it can be done.

Two,
The results of the Mendelian randomization study indicated that accelerometer-based physical activity, but not self-reported activity, does appear to protect against the risk of depression. The differences between the two methods of measuring physical activity could result not only from inaccuracies in participants’ memories or desire to present themselves in a positive way but also from the fact that objective readings capture things other than planned exercise – walking to work, climbing the stairs, mowing the lawn – that participants may not recognize as physical activity. The analysis revealed no causal relationship in the other direction, between depression and physical activity.
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self-reported activity data is not as accurate as accelerometer recorded activity data.

Nothing earth-shattering but I thought it was nice that the two points were confirmed completely independently.
 
(off topic)

is it purely the physical activity, or is it partly the interaction with your local community and built / natural environment, that decreases depression ?

i'd like to see this research repeated, with wheelchair/aid dependent people. arbitrary goal of leaving the house (using aids), with subsequent benefits of being amidst your local community; opportunity to nod, smile, chat briefly with neighbours and interact with strangers; be among trees rivers birds animals wildlife weather; choose where you want to travel, explore new places shops cafes ...

my happiest moments are wandering about randomly on my mobility scooter, meeting people, enjoying the scenery etc.
 
It’s good to have hard data on those two items.

On the original study, I would also wonder about confounding. Did whatever led to the depression also cause the reduction in activity?

I am not sure they’ve actually proved causation. Post hoc ergo proper hoc (after this therefore because of this) is considered a logical fallacy.

There’s an association is all I can see they can assert, from what I read in the article.
 
Conclusions and Relevance Using genetic instruments identified from large-scale GWAS, robust evidence supports a protective relationship between objectively assessed—but not self-reported—physical activity and the risk for MDD. Findings point to the importance of objective measurement of physical activity in epidemiologic studies of mental health and support the hypothesis that enhancing physical activity may be an effective prevention strategy for depression.
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https://jamanetwork.com/journals/jamapsychiatry/article-abstract/2720689
 
A further thought I had on this. I can't get my head around if the Biobank cohort is the one with the accelerometers. If it is, would there be any value in looking for any of that cohort who are diagnosed with ME (or CFS as it most probably will be) and analysing the data? If there are pwME who wore accelerometers, compare them to healthy wearers, or other illness groups, as an example.
 
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