Beyond the unhealthy trappings of mood disorders, such as smoking and a poor diet, studies link biological changes to vascular deterioration.
THE QUESTION: A close friend has been troubled by manic depression for many years. She's now in her 40s and recently found out that she already has signs of heart disease. Is there anything that actually links depression to heart problems?
THE ANSWER: Numerous studies have found that patients who suffer from either depression or bipolar disorder face elevated chances of getting heart disease at an early age.
"It is quite clear there is an increased risk of coronary artery disease, which ultimately causes heart attacks," says Dr. Benjamin Goldstein, director of the Centre for Youth Bipolar Disorder at Sunnybrook Health Sciences Centre in Toronto.
Of course, many people who struggle with major depression or bipolar disorder – also known as manic depression – adopt habits that can contribute to the development of heart disease.
For instance, their psychiatric disorders increase the likelihood that they will smoke, not exercise regularly, and fail to stick to a healthy diet. What's more, some of the medications used to treat these conditions can cause weight gain, as well as alter cholesterol and blood-sugar levels in ways that can be bad for the heart.
But even in studies that control for the effects of lifestyle and medications, these patients are still more prone to get heart disease early compared with the general population.
"Their rate of heart disease goes well beyond what we would expect to see with traditional cardiovascular risk factors," Goldstein says. "Smoking, a sedentary lifestyle and poor nutrition just doesn't explain the whole story. So, there is something else going on."
People with bipolar disorder develop heart disease an average of 17 years sooner than those without a psychiatric condition. This means that when they're in their mid-40s, they already resemble individuals in their late 50s or early 60s in terms of the condition of their blood vessels.
Similar trends, although not as extreme, are seen in people who suffer from major depression. This group show signs of heart disease an average of six years sooner than would ordinarily be the case.
"It's like premature aging – and people are literally dying early because of this," Goldstein says.
So how does depression set the stage for heart problems? Goldstein says mood disorders are linked to a wide range of biological changes that seem to speed up vascular deterioration.
In particular, people with bipolar disorder and depression tend to have increased levels of inflammation – and inflammation, in turn, is known to boost the risk of cardiovascular disease.
During a manic episode or a bout of depression, inflammatory markers – such as C-reactive protein – proliferate in the blood stream. Once the mania and depression subside, the inflammatory markers return to normal levels.
"Inflammation is your body's immediate response to any threat, such as an injury, an infection or even stress," Goldstein explains. "At the right time, and in the right amount, inflammation is superimportant for maintaining health."
However, prolonged inflammation can be harmful. The cascade of proteins released by the inflammatory process can damage the inside lining of blood vessels. This can result in a buildup of plaque and other deposits, narrowing the arteries, and ultimately leading to heart disease.
Those who suffer from bipolar disorder are particularly vulnerable to the effects of inflammation because they can experience repeated periods of manic behaviour and depressive episodes over many years.
"If you have a few weeks of depression in your whole life, the magnitude of increased risk is pretty modest," says Goldstein. "But if you're 50 years old and have spent half the past decade depressed, then the risk is probably substantially elevated."
Aside from inflammation, mood disorders can cause other changes in the body that fuel the advance of heart disease. Studies show that depression is linked to an increase in the stickiness of platelets, which cause blood to clot. As well, there is evidence suggesting depression affects the autonomic nervous system that regulates the heartbeat.
"There are many different mechanisms and we don't fully understand them all," says Dr. Brian Baker, a psychiatrist and associate professor at the University of Toronto.
Some researchers even speculate that certain genetic traits may predispose some individuals to both mood disorders and heart disease.
Goldstein believes physicians should pay more attention to the onset of heart disease in young people with mood disorders. Unfortunately, it's often overlooked because health-care providers are primarily focused on treating the depression and the mania. And the relatively young age of the patients make them less obvious candidates for cardiovascular-disease prevention.
"When you look at the data, you realize that we need to start addressing this issue early on," Goldstein says. "There is a lot to be gained by increased recognition and knowledge about the higher heart-disease risk faced by this group of patients."
Paul Taylor is a Patient Navigation Advisor at Sunnybrook Health Sciences Centre. He is a former health editor of The Globe and Mail. You can find him on Twitter @epaultaylor and online at Sunnybrook's Your Health Matters.