There are a number of studies which links depression with physical activity; however, the question still remains unanswered that whether high rates of exercise reduce rates of depression or depression makes the person less efficient? Recent research led by Massachusetts General Hospital (MGH) scientists has proved physical activity as one of the best ways to prevent depression. The study is published online in the journal JAMA Psychiatry.
Karmel Choi, Ph.D., of the Psychiatric and Neurodevelopmental Genetics Unit in the MGH Center for Genomic Medicine and lead author of the study said: “Using genetic data, we found evidence that higher levels of physical activity may causally reduce the risk for depression. Knowing whether an associated factor actually causes an outcome is important because we want to invest in preventive strategies that really work.”
The novel method different from the traditional one was used in the study called Mendelian randomization to study the effects of genetic factor using different gene variants. The study of gene variants acts as a natural experiment, where people either show high level or low level of that specific factor like physical activity; these factors are linked to gene variants and differ due to inheritance.
As genetic variants do not have a specific pattern when it comes to inheritance they can help in understanding the interconnection between physical activity and depression more accurately. The random pattern ensures a reduced bias and that in turn helps in ensuring that the results are more precise and accurate. This method also makes easy to understand that which element is actually causative. For example, if element A is causing an effect on element B then element B cannot effect element A and vice versa.
For carrying out the study the researchers took help from the data of the large scale genome-wide association studies (GWAS) that were carried out to observe the physical activities in the U.K. Biobank and for depression as well in the global research consortium. The GWAS data for physical activity had two categories one who reported their physical activities (377,000 participants) and one who worn motion sensitive-sensors like accelerometers on their wrists (91,000 participants) to calculate the rate of their physical activity.
The GWAS holds data of more than 143,000 participants for depression. This includes both types of participants that is who was going through this condition as well the ones without this condition.
As per the analysis of the study, physical activity using accelerometer played a key role in protecting the participants against depression while the self-reporting physical activity did not. It is maybe due to the fact that both the methods of measuring activities have a large difference in their accuracies as the self-reporting physical participants may have not considered walking, climbing the stairs, mowing the lawn, and other things as physical activities.
The difference in the result can also be due to the inaccuracy in the participants’ memory. The study only showed a relation of single direction between physical activity and depression.
Choi said: “On average, doing more physical activity appears to protect against developing depression. Any activity appears to be better than none; our rough calculations suggest that replacing sitting with 15 minutes of a heart-pumping activity like running, or with an hour of moderately vigorous activity, is enough to produce the average increase in accelerometer data that was linked to lower depression risk.”
Senior author Jordan Smoller, MD, ScD, director of the Psychiatric and Neurodevelopmental Genetics Unit and a professor of Psychiatry at Harvard Medical School, said, “While gene variants like those used in this study do not determine a person’s behaviors or outcomes, their average associations with certain traits in these very large studies can help us look at a question such as whether physical activity—or the tendency to engage in more physical activity—has a likely causal effect on depression. And the answers to those questions could help researchers design large-scale clinical trials.”
Choi further explains, “And of course it’s one thing to know that physical activity could be beneficial for preventing depression; it’s another to actually get people to be physically active. More work needs to be done to figure out how best to tailor recommendations to different kinds of people with different risk profiles.
We currently are looking at whether and how much physical activity can benefit different at-risk groups, such as people who are genetically vulnerable to depression or those going through stressful situations and hope to develop a better understanding of physical activity to promote resilience to depression.”