Depression and cardiovascular risk

We rarely think about the heart when talking about depression. Yet the two are linked in both directions: depression increases the risk of cardiovascular disease, and heart disease increases the risk of depression. This link, studied for more than thirty years, is one of the reasons why mental health is fully part of cardiovascular prevention.

The stakes are significant on both sides. Cardiovascular disease is the leading cause of death worldwide, with about 18 million deaths a year according to the WHO, and the leading cause in the United States. In France, it is the second leading cause of death, with about 140,000 deaths a year. Depression, for its part, affects nearly one adult in six in France over the course of a year, according to Santé publique France.

A risk factor documented for decades

A frequently cited Dutch study, published in 2001 in Archives of General Psychiatry (Penninx et al.), followed nearly 3,000 older adults for about four years. Major depression was associated there with a roughly 3-fold increase in the risk of cardiac death among people who already had heart disease, and nearly 4-fold among those who did not, after accounting for other risk factors.

These high figures concern an older population and major depression specifically. Large reviews give more modest, but consistent, orders of magnitude. A meta-analysis published in 2014 in BMC Psychiatry (Gan et al.), pooling around thirty cohort studies, estimated that depression increased the risk of developing coronary heart disease by about 60% and the risk of coronary death by about 30%. Other research shows a similar association with stroke. The risk rises with symptom severity, which reinforces the idea of a genuine link.

A markedly higher recurrence risk after a first event

The link is even clearer after a cardiac or vascular event. About one person in five has major depression in the months following a heart attack, and many others have less intense depressive symptoms. After a stroke, nearly one patient in three has depression, according to a meta-analysis published in 2014 in the International Journal of Stroke (Hackett and Pickles).

In these patients, depression is associated with roughly twice the risk of a new cardiovascular event or death in the following years. The evidence is strong enough that the American Heart Association published a scientific statement in 2014 recommending that depression be considered a risk factor for poor prognosis after acute coronary syndrome. European cardiology guidelines likewise recommend screening for depressive symptoms in cardiac patients.

Part of this excess risk comes from the fact that depression makes the care pathway harder to follow after a cardiac event: less participation in cardiac rehabilitation, more frequent relapse into smoking, and less regular use of prescribed treatments.

An even stronger association when conditions combine

Depression and anxiety often go together. Several studies suggest that people with both conditions have a higher cardiovascular risk than those with only one of the two, even after accounting for lifestyle and standard risk factors. Other psychosocial factors are often added on top: social isolation, chronic work stress, financial difficulties. The large international INTERHEART study (Rosengren et al., The Lancet, 2004), conducted in 52 countries, showed that psychosocial stress, including depression, was among the leading risk factors for heart attack, alongside smoking, hypertension, and diabetes.

Why this link exists

Two broad families of mechanisms explain this association.

The first are biological. Depression comes with prolonged activation of the body's stress-response systems: cortisol and adrenaline stay elevated, which promotes hypertension, raised blood sugar, and abdominal fat accumulation. Low-grade chronic inflammation is also seen, measurable through blood markers such as C-reactive protein, which contributes to arterial wear. Blood platelets tend to clump together more easily, promoting clot formation. Finally, heart rate variability, a reflection of the heart's ability to adapt, is often reduced, which is associated with a risk of rhythm disorders.

The second are behavioral. Depression reduces energy and motivation, making it harder to exercise, eat well, quit smoking, limit alcohol, or sleep properly. It also complicates medical follow-up: missed appointments, blood pressure or cholesterol treatments taken irregularly. These behaviors are themselves cardiovascular risk factors, and they explain a significant part of the link.

The link also runs through other risk factors. Depression is associated with a higher risk of type 2 diabetes, by about 60% according to a meta-analysis published in Diabetes Care in 2008 (Mezuk et al.), and diabetes in turn increases the risk of depression. Sleep disorders, very common in depression, are themselves associated with hypertension and cardiovascular risk. If sleep is very disrupted, the Do I have sleep apnea? and Am I at risk of diabetes? tests can help you take stock.

The relationship also works the other way around. Living with heart disease, having feared for one's life, having to change habits or stop working can all contribute to depression. There's even a specific type of heart condition, tako-tsubo syndrome, or “broken heart syndrome,” triggered by intense emotional stress. It remains rare and is most often reversible.

What this means in practice

This evidence justifies including mental health in cardiovascular assessments, and conversely, thinking about the heart in people with depression. The two dimensions of health are interdependent.

An honest question arises: does treating depression reduce cardiovascular risk? Large trials have shown that depression treatments, whether psychotherapy or antidepressants such as sertraline, are effective and safe in cardiac patients. This is what the SADHART (2002) and ENRICHD (2003) trials established. However, they did not clearly demonstrate a reduction in cardiovascular events. Treating depression remains, of course, essential for quality of life, and it helps restore the energy needed to take care of your heart: resuming physical activity, quitting smoking, following treatment.

In practice, if you have a high score on the depression test, it can be useful to also take stock of your cardiovascular risk factors, with the What's my cardiovascular risk?, Do I have high blood pressure? or Am I dependent on tobacco? tools. Conversely, if you've had a heart attack or stroke and feel persistently down, talk to your cardiologist or doctor about it: this isn't a “normal” reaction to endure in silence, and it can be treated.

Physical activity is a good example of a shared lever. It improves depressive symptoms, as many trials have shown, and it reduces cardiovascular risk. Even modest and gradual, it acts on both fronts at once.

To assess your symptoms, take the “Am I depressed?” test.