"If one isn't well, the other often suffers too," says Dr Volker Köllner, medical director and chief physician of the Department of Psychosomatic Medicine at the Seehof Rehabilitation Centre in Teltow, near Berlin.
And so sometimes it's not enough to treat just one or the other, Köllner says. If you have a cardiological problem, it can be helpful to look at possible psychological causes - and vice versa. There's even a special medical discipline devoted to the interaction between the heart and mind: psychocardiology.
Many studies have shown the two to be closely linked; depression, for example, increases the risk of a heart attack almost as much as smoking does.
"We also know that stress experienced early in life can cause disease," Köllner says. "If you were a victim of violence or sexual abuse in your childhood, you're at greater risk of a heart disorder, which may not appear until decades later."
Sudden, extreme stress, such as the death of a loved one or loss of your job, can disrupt your heart's usual pumping function and mimic the symptoms of a heart attack. This phenomenon is known as broken heart syndrome and can require treatment in a hospital intensive care unit. The condition is usually transient, however.
A much more frequent cause of heart problems is chronic stress, the body's reactions to which damage the heart over time.
Playing the central role here is the autonomic nervous system, which regulates involuntary physiological processes including heartbeat, blood pressure, breathing and digestion. When we're under stress, our heart beats faster - part of the "fight or flight" response - and our blood platelets stick together more readily, helping to form clots that stop bleeding.
"Our body prepares itself for [possible] injury," says Dr Christoph Herrmann-Lingen, director of the Department of Psychosomatic Medicine and Psychotherapy at the Göttingen University Medical Centre in Germany. An unwanted consequence of this is a heightened risk of narrowed coronary arteries.
When the cardiovascular system is constantly put into a state of alert, high blood pressure can result as well, possibly damaging coronary arteries and increasing the risk of a heart attack or heart failure.
What's more, people often behave in unhealthy ways in times of stress. Some may shelve their weekly tennis workout and smoke more cigarettes, others may shift their diet to predominantly fast food. All of these things are risk factors for heart disorders. So the key to prevention is sticking to healthy routines even in stressful periods of your life.
Conversely, heart problems can impact mental health. "Heart disease, such as a heart attack, isn't like a sprained ankle," says Hermann-Lingen. "An event of this kind can undermine your fundamental trust in your body."
Anxiety and apprehensiveness are normal psychological reactions, particularly in the early aftermath of a heart attack. "Most patients' psyche normalizes after a while," Köllner says. Most, but not all.
"Some patients pay excessively close attention to their body, trying to recognize any harbingers of another heart attack," Herrmann-Lingen says. This results in high stress levels and can keep patients from making demands on their body, "although regular physical activity is important, as it lowers the risk of further heart problems as well as depression."
To break this vicious circle and align patients' concerns with their actual risks, it's advisable that they consult their doctor.
"There are many group cardiac rehab programmes that can be beneficial," says Köllner. They're offered by sport clubs and rehabilitation clinics as well as other organizations. Meanwhile,
psychotherapy can help patients regain trust in their heart and teach them better body awareness.
