Too little exercise and too much TV tied to depression

November 12, 2012

Too little exercise and too much TV tied to depression

A new study published online by the American Journal of Epidemiology, has suggested that middle aged women who avoided watching television whilst at the same time taking regular exercise had the lowest risk of being diagnosed with depression. According to Dr. Gillian Mead, who studies geriatric medicine at Edinburgh’s Royal Infirmary but had no involvement with the study, the report, “adds to the growing body of evidence that physical activity is important to maintain brain health”.

The study was large scale, involving nearly 50,000 women who were part of the U.S. Nurses’ Health Study. They completed questionnaires every two or three years detailing time spent on activities like walking, cycling, running and swimming from 1992 to 2000. They also completed questions relating to their viewing habits in 1992. The follow up questionnaires also recorded any new diagnoses, such as clinical depression and any medicines prescribed for the condition.

The analysis of the data only related to females with no diagnosis of depression in 1992. At that time the average age of the participants was between 63 and 64 years. In the intervening period 6,500 new cases of clinical depression were diagnosed.

The researchers found that the women who reported doing the most amounts of exercise now and in the last few years were about 20% less likely to develop depression than those who lived a sedentary lifestyle. However women who spent more time watching television increased their risk of depression. But the increased risk was less than 20%.

Avoiding exercise or watching too much television cannot be proven to be the cause of developing depression, however the researchers say that more exercise will raise the endorphin level in an individual, enhancing their self esteem and boosting confidence.

The researchers took into account all of the lifestyle factors which may have an association to depression. This meant that age, weight, medical history and the amount of exercise taken were all addressed. The researchers found that if a woman worked out for more than an hour and a half every day then her risk of depression dropped to 20% less than those who did less than 10 minutes exercise a day.

The study author Michel Lucas, from the Harvard School of Public Health in Boston, said, “If you walk at an easy pace and slow pace, probably you will not get the benefits people have when they walk at a brisk or very brisk pace”. This was said to clarify the importance of exercising with the correct level of intensity. Women reported walking as the most common type of exercise but the researchers noted that only the women who walked briskly saw any benefits of lower rates of depression.

One finding, which the researchers could not validate, it could be due to chance, was that women who watched television for more than 3 hours a day had a 13% higher chance of being diagnosed with depression compared to other who did not watch TV.

Lucas applies common sense when he points out that if women are watching TV then they are not exercising and so to say that the link is between TV and depression is not altogether true. It is more likely to be the lack of exercise that is the issue.

Previous research has also identified that exercise can produce positive effects when mental health is considered. Mead acknowledges that this study adds to the body of evidence relating to depression and exercise and says, “Previous studies have suggested that physical activity is associated with a lower risk of depressive symptoms”. But, “it cannot prove a causal relationship between low physical activity and depression,” she added.

Another reason for the findings has been explained by the researchers. They comment that perhaps the women were already becoming depressed but had not had any diagnosis. This would alter their lifestyle causing them to exercise less and sit around watching TV to kill time. The formal diagnosis, coming at a later date, would reflect on their findings.

Irrespective of other things Lucas believes that more time exercising instead of watching television can only be of benefit to the women and lower their chances of becoming depressed.

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