Research has shown that heart attacks increase during the winter months, with Christmas and New Year’s being especially deadly. Now a new study finds that emotional stress caused by the holiday season may be to blame.

A team of researchers led by cardiologist Robert Kloner looked at factors that contributed to heart attacks in Los Angeles during 2004. They found that cardiac deaths rose 33 percent between November and January and peaked on Christmas and New Year’s. After considering a variety of possibilities for the cause, they concluded that stress associated with the holidays is a primary factor.

Dr Kloner explains that stress stimulates the sympathetic nervous system and causes the release of catecholamines, which increase heart rate, blood pressure, and the force of the heart’s contractions. This can intensify the pressure of the blood against plaque in the arteries and can cause the plaque to rupture and possibly block blood flow. These blood clots can shut off blood flow in the coronary artery and cause a heart attack.

Reducing stress is considered vital to maintaining optimum health. According to the Mayo Clinic, natural stress relief techniques include eating a healthy diet, exercising regularly and practicing techniques like yoga, meditation and tai chi.