Some people say depression leads to a broken heart. It's a catchy expression, but is it really true?
There is certainly a link between depression and heart disease, the most common cause of a heart attack. People with depression are 30% more likely to develop heart disease than those without it.
It seems logical then that depression could, quite literally, break your heart.
However, our new research suggests rather than cause heart disease, depression in people aged 45 or older can signal the early signs of the disease and the need for a heart check.
How are depression and heart disease linked?
To say one thing causes another, we first need to understand how the two things are linked, including which comes first.
Does depression lead to an event like a heart attack? Or are there early signs of heart disease – which make people much more likely to have a heart event – that lead to depression?
We know depression has physical effects on the body, some of which may harm the heart. Depression can increase inflammation, heart rate and blood pressure, all of which are involved in developing heart disease.
However, it's also true people with early heart disease can feel physically lousy long before a life threatening heart event.
Half of people who survive a heart attack say they had heart disease symptoms leading up to it. The most common early signs were fatigue, shortness of breath and pains in the chest, arm, neck or back. If experienced for long periods of time these symptoms can leave a person feeling depressed.
Depression can also be linked to heart disease through behaviours and other chronic diseases. Smoking, not exercising enough, heavy drinking and poor diet, and chronic conditions like diabetes, are all more common in people with depression. These are all also factors involved in developing heart disease.
So before we can claim depression breaks your heart, we must account for the fact some behaviours and chronic diseases are more common in this group, and some people may have depression because of the early signs of heart disease.
This is exactly what our study did.
What our study found
We used data from more than 150,000 people 45 years or older who had not already had a heart attack or stroke.
At the start of the study people reported their level of psychological distress, a commonly used measure of symptoms of depression and anxiety. We then followed them over five years to see how many developed heart disease.
People with the highest levels of psychological distress were 70% more likely to go on to have a heart event (like a heart attack) within the next few years than people with the lowest levels of psychological distress.
After taking smoking, exercise, alcohol, weight and diabetes into account, this dropped to just 40%.
When we excluded people with early signs of heart disease, there was little evidence psychological distress increased the risk of developing heart disease at all.
This suggests it's more helpful to view depression as something that signals a higher risk of heart disease, rather than as a direct cause of the disease.
This is in line with findings from other large-scale studies and robust trials. These have found treating depression does not reduce the risk of developing heart disease. If depression caused heart disease, we would have expected treating depression to have reduced the chance of developing heart disease.
If you have depression, get a heart check
The finding that depression is unlikely to cause heart disease suggests depression in people aged 45 or older might be an important sign of other things going on.
If you experience depression, talk to your doctor about it and how treatments can help.
If you're 45 or older, while you're with your doctor, ask for a heart check. This is the first step to assessing your future risk of heart disease. It also helps your doctor find the best way to lower your risk.
Explore further: Exercise reduces heart disease risk in depressed patients