| Health / Health News |
Inflammation links heart disease and depression
The link between heart disease and depression is well documented. People who have a heart attack are at a significantly higher risk of experiencing depression. Yet scientists have been unable to determine whether this is due to the two conditions sharing common genetic factors or whether shared environmental factors provide the link.
Depression. 
While inflammation is a natural response necessary to fight off infection, chronic inflammation – which may result from psychological stress as well as lifestyle factors such as smoking, excessive alcohol intake, physical inactivity and obesity – is harmful.
“It is possible that heart disease and depression share common underlying biological mechanisms, which manifest as two different conditions in two different organs – the cardiovascular system and the brain,” says Dr Golam Khandaker, a Wellcome Trust Intermediate Clinical Fellow at the University of Cambridge. “Our work suggests that inflammation could be a shared mechanism for these conditions.”
First, the team looked at whether family history of coronary heart disease was associated with risk of major depression. They found that people who reported at least one parent having died of heart disease were 20% more likely to develop depression at some point in their life.
Next, the researchers calculated a genetic risk score for coronary heart disease – a measure of the contribution made by the various genes known to increase the risk of heart disease.
Heart disease is a so-called ‘polygenic’ disease – in other words, it is caused not by a single genetic variant, but rather by a large number of genes, each increasing an individual’s chances of developing heart disease by a small amount. Unlike for family history, however, the researchers found no strong association between the genetic predisposition for heart disease and the likelihood of experiencing depression.
Together, these results suggest that the link between heart disease and depression cannot be explained by a common genetic predisposition to the two diseases. Instead, it implies that something about an individual’s environment – such as the risk factors they are exposed to – not only increases their risk of heart disease, but at the same time increases their risk of depression.
They used a technique to investigate 15 biomarkers – biological ‘red flags’ – associated with increased risk of coronary heart disease.
Of these common biomarkers, they found that triglycerides (a type of fat found in the blood) and the inflammation-related proteins IL-6 and CRP were also risk factors for depression.
Both IL-6 and CRP are inflammatory markers that are produced in response to damaging stimuli, such as infection, stress or smoking.
Studies have previously shown that people with elevated levels of IL-6 and CRP in the blood are more prone to develop depression, and that levels of these biomarkers are high in some patients during acute depressive episode. Elevated markers of inflammation are also seen in people with treatment resistant depression. This has raised the prospect that anti-inflammatory drugs might be used to treat some patients with depression.
While the link between triglycerides and coronary heart disease is well documented, it is not clear why they, too, should contribute to depression. The link is unlikely to be related by obesity, for example, as this study has found no evidence for a causal link between body mass index (BMI) and depression.
Taking a holistic view of a person’s health – such as looking at heart disease and depression together – enables us to understand how factors like traumatic experiences and the environment impact on both our physical and mental health. (University of Cambridge)
YOU MAY ALSO LIKE
