A new study looks into the link between heart disease risk and depression.

People have been captivated by the connections between mind and body for aeons. Do people truly die of a shattered heart, for example? Is it true that a healthy mind equals a healthy body?

For a long time, scientists have been researching the links between mental and physical health. Depression and heart disease are one example of such a link. Depression is more common in patients with heart disease than in the general population, according to research.

Furthermore, persons with increased depressive symptoms are more likely to acquire the cardiac disease than those who do not have depression when monitored over a long period of time in physically healthy adults.

We also know that having depression is linked to an increased risk of further heart attacks and mortality, not just from heart disease, but from any cause, in persons with acute heart illness (for example, if they've had a heart attack).

However, less research has looked at whether these tendencies might be reversed, that is, whether cardiovascular risk factors are linked to a higher risk of depression. However, a new study published in the journal PLOS ONE aimed to investigate this.

What the scientists did

Sandra Martn-Pelez and her colleagues from the University of Granada in Spain studied persons with metabolic syndrome to see if there was a link between cardiovascular risk factors and depression in people aged 55 to 75.

Metabolic syndrome is a combination of illnesses that occur together and raise a person's risk of heart disease, stroke, and type 2 diabetes. It includes high blood pressure, high blood sugar, extra body fat around the waist, and elevated cholesterol. According to some researchers, metabolic syndrome may also play a role in depression.

This study drew participants from a larger study looking at the effects of a Mediterranean diet on persons who are overweight or obese and have metabolic syndrome. One group follows a calorie-restricted Mediterranean diet plus a physical activity programme, whereas the other follows an unrestricted Mediterranean diet without a physical activity programme in the ongoing randomised experiment.

Surprisingly, no significant link was discovered between cardiovascular risk and depression at either the baseline or follow-up levels. So, in general, those who were at a higher risk of heart disease were not more likely to have or develop depression.

When the authors examined the data by gender, they discovered that women with higher cardiovascular risk were more likely to demonstrate signs of depression from the start. However, this was not the case in males, and it was not the case in either men or women at the follow-up.

At two years, the depression ratings of all subjects had decreased on average. Depression levels fell more in individuals with minimal cardiovascular risk and in those in the intervention group (participants who were following the restricted diet and the physical activity programme).

The conclusions of this study are difficult to understand. The data has been analysed in a variety of ways, yielding varied findings. The authors, for example, examined the data by different metabolic syndrome components and discovered that diabetes and particular cholesterol levels resulted with reduced depression scores at follow-up.

However, other studies have shown that women with heart disease had greater levels of depression than males with heart disease. It is also commonly known that women have greater rates of depression than males in the general community. As a result, the discovery that there may be a relationship between heart disease risk and depression in women appears to be consistent with these patterns.

What is the connection between depression and heart disease?

Although we cannot conclude from this study that a higher risk of having heart disease is related to a higher chance of acquiring depression, it does add to an already substantial body of data showing a relationship between heart illness and depression.

This link might be explained by a variety of behavioural and biological reasons. Some of the biological components that are common to both depression and the risk of heart disease are as follows:

Endothelial dysfunction due to increased inflammation (constriction of blood vessels in the heart)
abnormal activation of the autonomic nervous system (the autonomic nervous system controls muscles, including the heart)
platelet malfunction in the blood (where blood platelets are more likely to stick together and form clots).

Furthermore, we know that good lifestyle variable like physical exercise, avoiding smoking, and eating a nutritious diet protect against both heart disease and depression. The inverse is also true: bad lifestyle choices are linked to an increased risk of heart disease and depression.

Unfortunately, those suffering from depression have a more difficult time changing such behaviours, such as quitting smoking. The most intriguing conclusion of this study is that depression levels were lower in the group that was urged and supported to adopt a better lifestyle, which included a more restrictive diet and more physical activity.

While there is strong evidence that exercise is a very effective treatment for depression in persons with heart disease, the significance of nutrition as a depression intervention is less obvious. This study provides a positive motivation for further research into nutrition and lifestyle as potential depression therapies in those who have or are at risk of having heart disease.